Identification, Mitigation, and Adaptation
to Salinization on Working Lands
in the U.S. Southeast
Nancy Gibson
Steven McNulty
Chris Miller
Michael Gavazzi
Elijah Worley
Dan Keesee
David Hollinger
United States Department of Agriculture
Forest Service
Southern Research Station
General Technical Report SRS-259
January 2021
Authors
Nancy Gibson, Research Assistant, USDA Southeast
Regional Climate Hub, Research Triangle Park,
NC 27709-2254; Steven McNulty, Director, USDA
Southeast Regional Climate Hub, Research Triangle
Park, NC 27709-2254; Chris Miller, Manager/Plant
Specialist, USDA-NRCS, Cape May Court House,
NJ 08210; Michael Gavazzi, Coordinator, USDA
Southeast Regional Climate Hub, Research Triangle
Park, NC 27709-2254; Elijah Worley, Research
Assistant, USDA Southeast Regional Climate
Hub, Research Triangle Park, NC 27709-2254;
Dan Keesee, Conservationist, USDA-NRCS, Temple,
TX 76501; and David Hollinger, Director, USDA
Northeast Climate Hub, Durham, NH 03824.
Disclaimer for External Links
The appearance of external hyperlinks does not constitute endorsement by the
Department of Agriculture of the linked web sites, or the information, products
or services contained therein. Unless otherwise specified, the Department
does not exercise any editorial control over the information you may find at
these locations. Please let us know about existing external links you believe are
inappropriate and about specific additional external links you believe ought to
be included.
Disclaimer of Non-endorsement
Reference herein to any specific commercial products, process, or service by
trade name, trademark, manufacturer, or otherwise, does not necessarily
constitute or imply its endorsement, recommendation, or favoring by the
United States Government. The views and opinions of authors expressed herein
do not necessarily state or reflect those of the United States Government, and
shall not be used for advertising or product endorsement purposes.
Cover Photograph: Fields of corn are flooded and crops may be ruined for the
year by the flooding waters of the Mississippi River in southern Illinois. (Photo
courtesy of Robert Kaufmann, FEMA)
January 2021
https://doi.org/10.2737/SRS-GTR-259
Forest Service
Research & Development
Southern Research Station
General Technical Report SRS-259
Southern Research Station
200 W.T. Weaver Blvd.
Asheville, NC 28804
www.srs.fs.usda.gov
Identification, Mitigation, and Adaptation
to Salinization on Working Lands
in the U.S. Southeast
Nancy Gibson
Steven McNulty
Chris Miller
Michael Gavazzi
Elijah Worley
Dan Keesee
David Hollinger
Key Messages
• Soil salinization in the coastal Southeastern
United States is becoming more prevalent as storm
surges increase in frequency and sea levels rise.
• Salinization reduces the productivity of working
lands and can prevent crops from growing.
• Resources are lacking for landowners to
understand coastal salinization and how to
manage for resilience.
• Action must be taken if the land is to remain
profitable as conditions change.
This manual describes the impacts and includes
adaptation measures that can be taken to maintain
productivity in working lands.
Keywords: Adaptation, agriculture, saline soil,
salinity, salinization, sea-level rise.
Acknowledgments
USDA Southeast Climate Hub
USDA Natural Resources Conservation Service
USDA Office of the Chief Economist
USDA Office of Sustainability and Climate
USDA Northeast Climate Hub
North Carolina Climate Office
Kate Tully
Keryn Gedan
LeeAnn Haaf
Ellie Davis
Amy Jacobs
Jackie Specht
Contents
Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
CHAPTER 1
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
CHAPTER 2
Assessing and Minimizing Salinity Risk to Soil . . . . . . . . . . . . . . . . 7
CHAPTER 3
Non-Impacted Uplands in Proximity to Impacted Lands . . . . . . . . . . . 16
CHAPTER 4
Commercial Upland Introduction of Salinity . . . . . . . . . . . . . . . . . 18
CHAPTER 5
Commercial Upland, Recurring Episodic Salinization . . . . . . . . . . . . .24
CHAPTER 6
Commercial Upland, Well Established, Chronic Salinization . . . . . . . . . 31
CHAPTER 7
Noncommercial Upland. . . . . . . . . . . . . . . . . . . . . . . . . . . .35
CHAPTER 8
Economic Case Study. . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
CHAPTER 9
Saltmarsh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
APPENDIX I
Useful Tools and Resources. . . . . . . . . . . . . . . . . . . . . . . . . .48
APPENDIX II
Native Plant Species Salt Tolerances by Condition . . . . . . . . . . . . . .50
APPENDIX III
Unit Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
APPENDIX IV
Electrical Conductivity (EC) Testing Laboratories by State . . . . . . . . . .53
APPENDIX V
Conservation and Farm Bill Programs . . . . . . . . . . . . . . . . . . . .54
Salinization Manual Glossary . . . . . . . . . . . . . . . . . . . . . . . . .57
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
Stage Zero
Stage One
Stage Two
Stage Three
Stage Four
Stage Five
vi
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Executive Summary
Droughts and heatwaves, floods, wildfires, and hurricanes dominate the
news. These disturbances can cause billions of dollars per event in damage
to agriculture and forestry. However, saltwater intrusion into the forest,
agricultural, and pastureland soils across eastern Coastal and Gulf States can
also negatively impact productivity and profitability. Saltwater intrusion’s
negative impacts include tree and crop death, reduced growth, and crop yield.
Even though biological productivity may still be possible, the economic value
in maintaining these working lands can be insufficient to justify continued use.
Although an exact number of acres being lost per year is not currently known,
low-elevation agricultural land in the Southeast is being lost. In Somerset
County, MD, 3.5 km
2
of agricultural land became tidal wetland between 2009
and 2017.
1
As the sea level rises, the number of acres impacted by salinization is
expected to increase.
Soil salinization driven by saltwater intrusion can occur due to sea-level
rise, storm surge, high tides that overtop low-elevation areas, drought, and
groundwater pumping, as well as other natural and anthropogenic events.
Increases in some types of salinization can be planned given our knowledge
of sea-level rise as predicted by the NOAA Sea Level Rise Viewer. However,
storm surges are unpredictable from tropical storms that develop quickly and
have unpredictable impacts. Storms can bring strong winds that push salts
Salt Marsh in Salcott Creek/Blackwater Estuary. (Photo courtesy of Matthew Barker, Wikimedia Commons; CC BY
2.0 license)
vii
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
inland, but they also bring precipitation that may help remove the soil salts
through leaching. This guide does not predict the rates of sea-level rise or soil
salinization but instead provides mitigation and adaptation practices that can
reduce soil salinization impacts on productivity. Managing for both storm and
sea-level rise will require different adaptation and mitigation practices. The
frequency and duration events can range from episodic (e.g., shorter duration,
but intense coastal storms and hurricanes) to chronic saltwater saturation from
sea-level rise and migrating tidal boundaries. Both climate change-induced
increases in the frequency and size of storms, and more frequent king [i.e.,
exceptionally large (perigean spring)] tides can push saltwater farther inland.
Much of the Southeast Atlantic Coast has experienced increases in nuisance
level flooding since the 1980s,
2
and sea levels have been rising at an accelerating
rate globally since the 19th century.
3
Droughts contribute to salinization by decreasing the amount of available
freshwater to flush salts out of soil and groundwater. Water management also
contributes to freshwater availability as withdrawal of surface and groundwater
for drinking water and irrigation reduce the amount of freshwater available
to prevent saltwater intrusion. Hydrological connectivity (e.g., tide gates,
valves, levees, agricultural diversions, roadside ditches, and canals) can impact
the extent of saltwater intrusion. For example, canals and ditches can act as
conduits for saltwater intrusion to reach farther inland, while tide gates and
valves can block saltwater from moving inland. Tide gates and valves can
Ghost forest in Nags Head Woods, NC. (Photo courtesy of NC Wetlands from Raleigh, NC; CC BY 2.0 license)
viii
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
be used to block intrusion. However, they can also lead to salinity issues if
saltwater is trapped behind them and unable to drain away.
Coastal Virginia, Maryland (Delmarva Peninsula), and North Carolina
(Albemarle Pamlico Peninsula) are notable areas where agricultural land is
currently negatively impacted by salinization. The area of impacted land is
expected to increase in size as sea levels rise and saltwater intrusion moves
farther inland. Additionally, hurricanes will continue to bring storm surge and
coastal flooding. Thus, there is a great need to identify the current and future
areas of soil salinization.
Mitigation measures, including leaching with freshwater and installing water
control structures to sustain land productivity at risk of salinization, can
be used when they are economically beneficial. Mitigation measures can be
attempted, but they are often costly and can be unproductive. Adaptation
measures can also be applied in preparation for potential inputs of saltwater.
Chronic saltwater inputs will inevitably require landowners to implement
adaptation measures, including planting more salt-tolerant crops to continue
gaining profit from the cultivation of the land.
This guide is designed to assist the producer (extension agents, landowners,
U.S. Department of Agriculture (USDA) Natural Resources Conservation
Service (NRCS) field staff, private consultants) in determining their land’s
stage of soil salinization. This is a general guide for the U.S. Southeast, and
specific recommendations will depend on the producer’s site characteristics.
Recommendations for mitigating soil salinization may be proposed based on
the cause and salinization stage. The guide also provides information regarding
expected production reductions for economically important crop species
and cultivars across various soil salinity levels. The salinization levels have
been divided into stages to allow the producer to assess the soil’s condition
and management options more easily. At some point, the land may no longer
be commercially profitable. Hence, the guide includes a chapter that helps
determine when farming or forestry is no longer advisable and when the land
could be better used as a conservation easement. The appendix includes lists of
useful links and resources containing information on the topics covered in this
guide. The recommendations and information provided in these chapters are
not meant to replace the need to meet with the county Extension specialist, soil
conservation district office, or other professional service providers.
1
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
CHAPTER 1
Background
Agricultural productivity provides safe, reliable, and affordable food and agricultural
products for the Southeastern United States. Agriculture is a crucial contributor to the
region’s economic growth and development. Agricultural productivity is impacted by
many factors, including soil fertility, water availability, climate, disease, insects, weed
control, pests, plant nutrients, and hybrid or variety selection. Many of these factors
cannot be controlled, but most can be managed. Salinity is an often-overlooked factor
that negatively impacts agricultural productivity in the U.S. Southeast. Salinization
in the Southeast is different from salinization in arid climates. The southeast system
is both wet and salty. Dry, salty systems, such as those found in arid and semi-arid
climates of the Western United States, have been studied for decades, but salinization
in wet systems typical of the Southeast presents unique problems. These unique
problems include the difficulty of salt removal from wet soils, compounded problems
due to waterlogging, and encroaching saline groundwater in coastal areas. Salinization
of soils can make land unfarmable. Rising sea levels contribute to soil salinization
through raising groundwater tables, increasing saltwater intrusion, and magnifying
storm surges in coastal lands.
4
Salinization is the accumulation of water-soluble salts in the soil. The accumulation
can occur very slowly (e.g., sea-level rise) or quickly (e.g., hurricane storm surge),
depending on a combination of factors driving salinization. In areas experiencing
subsidence, the relative increase in sea-level rise is faster because as the sea is rising,
the land is sinking. The Mid-Atlantic States of the Eastern U.S. have been identified
as especially vulnerable to coastal flooding due to the co-occurrence of increasing
sea-level rise and land subsidence rates. The Mid-Atlantic area has a sea-level rise rate
that is accelerating three to four times faster (3.8 mm yr
-1
) than the global average
(~1 mm yr
-1
)
5
. The timing of these impacts is variable and based on the occurrence
of tropical storms and sea-level rise, both of which vary tremendously along the east
and gulf coasts.
Often, the factors contributing to salinization are connected and work together to
accelerate salt accumulation. For example, an area experiencing chronic saltwater
intrusion may experience a drought, which concentrates the soil’s salts, leading to
a salinity spike. However, in some cases, salt-stressed coastal areas can recover to
background production levels if freshwater is returned to the system, such as following
a large precipitation event or through irrigation flushing of the soil.
Wind plays a significant role in determining how ocean water interacts with the
land. Storm surges can be more extensive and last longer depending on the wind
direction, the hurricane’s strength, the tide, and local hydrological conditions.
Large storm surges create more coastal damage from erosion, soil compaction, and
saltwater intrusion. Salinity could be introduced as droughts become more frequent.
There could be a seasonal salinity increase from groundwater and surface waters that
recover when the drought was over. There can be seasonal shifts in the freshwater-
saltwater interface due to seasonal changes in groundwater discharge rates and
2
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
water table depths. These interface changes generally occur in the summer season
when water use by vegetation is at its peak. Also, during peak water use, surface
waters can be low and subject to tidal flow.
Crop revenue, production costs, farm profitability, and land values can be
significantly reduced by salt in the soil. Many crops are yield-dependent, in that
higher yields reduce per-unit production costs. Small reductions in yield due to
salinization can adversely affect net returns per acre and erode profitability. Fully
understanding the impact of salinity on crop production is essential since adaptation
practices may extend agricultural land’s working life in many areas along the
southeast U.S. coast. Understanding how the land is changing will allow producers to
proactively plan for the future to minimize productivity declines.
Many crops have known thresholds of tolerance and slopes of decline (table 1) in
response to soil salinity.
6,7,8
Salinity is often measured through a solution’s electrical
conductivity (EC). The salinity threshold of a crop is the point of salinity (EC) at which
crop relative yield will begin to drop below 100 percent. The percent relative yield
of crops in all commodity types decreases as the salinity increases, but their average
decline rates are different (figs. 1–4). Individual crop yield decline values shown in
these figures were derived using methods from Maas and Gratten (1999).
The relative yield percentage was calculated using the equation from Maas and Gratten,
(1999):
Y
r
= 100–b (EC
e-a
)
where Y
r
is the relative crop yield, a is the salinity threshold expressed in dS m
-1
, b is the
slope expressed in percentage per dS m
-1
, and EC
e
is the mean electrical conductivity
of a saturated-soil extract taken from the root zone. The decline in percent yield in
individual crops varies within commodity type. Actual changes in yield will vary
depending on the specific crop genetic variety and site conditions. In this guide,
increasing salinity levels are described as salinity stages (table 2).
9
Understanding this
decline in productivity and the stage of salinity of the land is important to prepare for
future increases in salinity.
Soil salinity stress in trees appears as a decrease in overall vigor, increased insect
problems, sparse crown, low growth, mortality, short needle length in pines, small
foliage in hardwoods, and overall appearance of poor health. Salinity impacts forest
crops by reducing the amount of freshwater for tree use, generating osmotic stress
similar to drought stress. Salt stress can cause reduced carbon assimilation in seedlings
and produces weaker seedlings compared to non-stressed seedlings.
10
Higher salinity
levels and longer durations of exposure may cause salt burning, browning of leaves,
and eventual tree death. Salinization suppresses regeneration in tree species, and
impacted areas may be slow to recover after a storm that pushed saltwater far inland.
When soils are nonsaline, tree seedlings and saplings will regenerate after an event
as long as conditions are favorable (i.e., adequate sunlight, nutrients, moisture,
temperature, and soil characteristics). Trees can also be stressed from a saturated root
zone following a storm or due to an elevated water table due to sea-level rise. Therefore,
differentiating the cause of tree stress (i.e., soil salt or waterlogged soil) is essential. Soil
elevation often determines if forests will survive or drown. While many row crops have
experimentally determined salinity thresholds and slopes of reduction per unit
3
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Table 1—Crop thresholds and slopes as determined by experimental field and lab studies
Crop Botanical name
Threshold
(EC)
Slope
(%) Crop Botanical name
Threshold
(EC)
Slope
(%)
Artichoke, Jerusalem (Tabers) Helianthus tuberosus 0.4 9.6 Onion (bulb) Allium cepa 1.2 16.0
Asparagus Asparagus oicinalis 4.1 2.0 Onion (seed) Allium cepa 1.0 8.0
Barley Hordeum vulgare 8.0 7.1 Orange Citrus sinensis 1.3 13.1
Bean Phaseolus vulgaris 1.0 19.0 Orchardgrass Dactylis glomerata 1.5 6.2
Bean, mung Vigna radiata 1.8 20.7 Pea Pisum sativum 3.4 10.6
Bermuda grass Cynodon dactylon 12.0* 6.4 Peach Prunus persica 1.7 21.0
Blackberry Rubus macropetalus 1.5 22.0 Peanut Arachis hypogaea 3.2 29.0
Boysenberry Rubus ursinus 1.5 22.0 Pepper Capsicum annuum 1.5 14.0
Broadbean Vicia faba 1.6 9.6 Plum, prune Prunus domestica 2.6 31.0
Broccoli Brassica oleracea (Botrytis) 2.8 9.2 Potato Solanum tuberosum 1.7 12.0
Cabbage Brassica oleracea (Capitata) 1.8 9.7 Quinoa Chenopodium quinoa willd 3.0 1.9
Carrot Daucus carota 1.0 14.0 Radish Raphanus sativus 1.2 13.0
Celery Apium graveolens 1.8 6.2 Rice, paddy Oryza sativa 3.0 12.0
Clover, alsike Trifolium hybridum 1.5 12.0 Rye Secale cereale 11.4 10.8
Clover, berseem Trifolium alexandrinum 1.5 5.7 Ryegrass, perennial Lolium perenne 5.6 7.6
Clover, ladino/white Trifolium repens 1.5 12.0 Sesbania Sesbania exaltata 2.3 7.0
Clover, red Trifolium pratense 1.5 12.0 Sorghum Sorghum bicolor 6.8 16.0
Corn Zea mays 1.8 7.4 Soybean Glycine max 5.0 20.0
Cotton Gossypium hirsutum 7.7 5.2 Spinach Spinacia oleracea 2.0 7.6
Cowpea Vigna unguiculata 4.9 12.0 Squash, scallop Cucurbita pepo var. clypeata 3.2 16.0
Cucumber Cucumis sativas 2.5 13.0 Squash, zucchini Cucurbita pepo var. cylindrica 4.9 10.5
Eggplant Solanum melongena 1.1 6.9 Strawberry Fragaria x ananassa 1.0 33.0
Flax Linum usitatissimum 1.7 12.0 Sudangrass Sorghum sudanense 3.0** 9.1**
Foxtail, meadow Alopecurus pratensis 1.5 9.6 Sugar beet Beta vulgaris 7.0 5.9
Garlic Allium sativum 3.9 14.3 Sugarcane Saccharum oicinarum 1.7 5.9
Grape Vitus vinifera 1.5 9.6 Sweet Potato Ipomoea batatas 1.5 11.0
Grapefruit Citrus x paradisi 1.2 13.5 Tomato Lycoperscion lycopersicum 2.5 9.9
Guar Cyamopsis tetragonoloba 8.8 17.0 Tomato, cherry
Lycoperscion lycopersicum-
cerasiforme
1.7 9.1
Guava Psidium guajava 4.7 9.8 Triticale X Triticosecale 6.1 2.5
Guayule Parthenium argentatum 8.7 11.6 Turnip Brassica rapa (Rapifera) 0.9 9.0
Harding grass Phalaris aquatica 4.6 7.6 Vetch, common Vicia sativa 3.0 11.0
Lemon Citrus limon 1.5 12.8 Wheat Triticum aestivum 6.0 7.1
Lettuce Lactuca sativa 1.3 13.0 Wheat (semidwarf) Triticum aestivum 8.6 3.0
Muskmelon Cucumis melo 1.0 8.4 Wheat, durum Triticum turgidum 5.9 3.8
Sources: Maas and Gratten (1999),
6
NRCS Technical Notes (1996),
7
Conway (2001).
8
4
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Percent yield
Fruits
●
Row crops
●
Vegetables
●
Fruits
●
Forage/Cover Crop/Erosion Control
1
2 3 4
Commodity Type Productivity
100
90
80
70
60
50
40
30
20
10
0
Figure 1—Generalized commodity average of the decrease in yield across four stages of soil salinity.
Percent yield
Stages
100
90
80
70
60
50
40
30
20
10
0
Vegetable Crops
Asparagus
Squash, zucchini
Pea
Squash, scallop
Broccoli
Cucumber
Spinach
Cabbage
Celery
Pepper
Lettuce
Onion (seed)
Onion (bulb)
Carrot
1 2 3 4
Figure 2—Generalized vegetable crop changes in yield across four stages of soil salinity.
5
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Figure 4—Generalized row crop changes in yield across four stages of soil salinity.
Figure 3—Generalized fruit crop changes in yield across four stages of soil salinity.
1 2 3 4
Percent yield
Stages
Fruit Crops
Guava
Tomato
Plum, prune
Tomato, cherry
Grape
Eggplant
Muskmelon
Grapefruit
Peach
Orange
Lemon
Blackberry
Boysenberry
Strawberry
100
90
80
70
60
50
40
30
20
10
0
Percent yield
Stages
Row Crops
Rye
Guar
Wheat (semidwarf)
Barley
Sugarbeet/Red
Cotton
Triticale
Wheat, durum
Sorghum
Artichoke
Wheat
Soybean
Garlic
Peanut
Rice, paddy
Alfalfa
Corn
Flax
Sugarcane
Potato
Broadbean
Sweet Potato
Radish
Turnip
Artichoke
Bean, mung
Almond
Bean
100
90
80
70
60
50
40
30
20
10
0
1 2 3 4
6
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
increase in salinity, these values have not been determined for tree species. The
life cycle of trees is much longer than for crops, so long-term data are necessary to
determine the full effect of salinization. Thus, most studies have focused on seedling
impacts
11
or examining tree death following hurricanes and storms.
12
Adaptative or preventative measures or practices (e.g., field buffers, increasing
drainage capacity, cover crops to remove salinity, flushing) should be considered
along with their effectiveness and cost. For example, the plant material associated
with buffers and excavation costs to increase the width, depth, or ditching length
can be expensive. Soil salinization can also damage capital expenses like buildings,
equipment, and machinery. Equipment service life is shortened, maintenance costs
are elevated, and operating efficiency decreases due to salt corrosion. As capital items
are expensive, deciding whether to replace them can impact farm profitability. This
manual will provide some case studies as examples of the cost/benefit of managing
salinated soil crops.
Table 2—Soil salinity classes as defined by McGeorge
(1954)
9
and salinization stages as defined in this guide
Salinity class Stage Electrical conductivity (EC)
dS m
-1
or mmhos cm
-1
Nonsaline Zero 0–2
Slightly saline One 2–4
Moderately saline Two 4–8
Strongly saline Three 8–16
Extremely saline Four >16
left: Ghost forests along the Seward Highway, near Anchorage, AK. (Photo courtesy of Alan Grinberg; CC BY-NC-ND 2.0
license); right: Mangrove to marsh transition zone. (Photo courtesy of USGS)
7
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
CHAPTER 2
Assessing and Minimizing
Salinity Risk to Soil
2.1 General Discussion
Landowners and managers need science-based strategies to formulate sound
management plans in the face of climate change. Landowners need to understand
the causes of salinization and knowing how to take a soil sample for testing used to
measure salinity is useful. National Resources Conservation Service (NRCS) field staff
or the local extension agent can be contacted to assist with soil sampling or to sample
for the landowner. Salinity can change with depth in the soil profile. For certain crops,
salinity in the top soil layer can impact seed germination, in which case planting
seedlings would be better. Salinity in lower soil layers could move upward through the
soil profile during dry periods.
Salinization and Soils in the Coastal Zone
Soil salinization can occur due to changing water demands, sea-level rise, drought,
storm surge, groundwater pumping, and other natural and anthropogenic events.
13
Event frequency and duration can be episodic (e.g., intense coastal storms and
hurricanes) or chronic (e.g., saltwater saturation from sea-level rise and migrating
tidal boundaries). When saltwater along the coast inundates (i.e., floods) freshwater
and terrestrial soils, saltwater intrusion occurs at the top of the soil profile and moves
downward. The depth of intrusion during a saltwater flooding event depends on the
saltwater volume and how long saltwater remains on the soil surface. Wetter soils have
less pore space for saltwater to percolate, while dry soils allow more saltwater to move
downward. Additionally, the soil properties themselves determine the rate at which
water moves through the soil profile. Soils with higher clay content are less permeable
than those with high sand content, resulting in slower water movement in clay soils.
Saltwater can also start at the bottom of the soil profile and move upward in the form
of saline groundwater. For example, rising sea levels can impact freshwater aquifers
and increase the salinity of the groundwater. Groundwater can move upward through
the soil profile through capillary action. As water evaporates at the soil surface, deeper
water moves upward through the soil profile to replenish the evaporating water. As
the sea level rises, groundwater levels may also rise due to pressure from the saltwater-
freshwater interface, which is the point where saltwater and freshwater push against
each other. The sea level cannot rise without the upper boundary of the interface,
which makes freshwater levels rise.
The physical and chemical characteristics of soils influence the potential for salt
retention from coastal saltwater inundation (e.g., storm surge), intrusion (e.g., sea-level
rise), or both. This chapter evaluates soil properties and factors that can determine
salt retention in soils due to coastal saltwater inundation and intrusion. The soil risk
assessment evaluates the salt retention potential of soil properties alone but does
not consider the saltwater inundation, hydraulic gradients, or topography duration.
8
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Knowing the saltwater inundation duration is essential because the negative impacts
on crops will increase with more extended saltwater inundation. Inundation over 24
hours creates an oxygen-deficient condition for vegetation that are not flood-tolerant,
in addition to increasing the level of toxicity to plants from saltwater. Higher salinity
levels require the need to cultivate more salt-tolerant crops. However, if salinity levels
are reduced, less salt-tolerant crops could once again be profitable.
There is limited information regarding how the duration and frequency of saltwater
inundation impacts soil salinity. However, salinized soils may recover more fully as
the time between saltwater inundation events and freshwater inputs increase. The
long-term impact on soil productivity is dependent on the duration of inundation, soil
texture, and soil moisture conditions before inundation occurs. Producers may want
to consider irrigating non-saturated soils with freshwater before saltwater inundation
to protect against increases in salinity and long-term soil productivity consequences.
Producers may want to also consider irrigating saline soils with freshwater to assist
with flushing out salts that may have accumulated during an inundation event.
In addition to being productive working lands, non-salt-impacted coastal soils are also
a critical buffer for inland soils. Salinization, coastal erosion, and natural vegetation
loss can all occur if coastal soils become degraded. Understanding how salt is retained
and the impacts on coastal soils will increase a producer’s knowledge and ability to
cope with salinized soil migration.
The Retention of Salts and their Relation to Soil Properties
Several factors determine the retention of salts in upland soils due to saltwater
inundation. These factors are soil texture, saturated hydraulic conductivity, cation
exchange capacity, sufficient cation exchange capacity, and water table fluctuations.
Soils with higher sand content are likely to have good drainage and retain fewer salts,
while soils with higher clay content are less well-drained and more likely to retain salts.
Sandy soils have a lower cation exchange capacity, a lower extractable cation exchange
capacity, a higher saturated hydraulic conductivity, and typically have reduced impacts
from saltwater inundation. Saturated hydraulic conductivity is a measure of the
rate at which fluid moves through the soil, so soils with a high saturated hydraulic
conductivity drain well and are less susceptible to salinization. The cation exchange
capacity and the effective cation exchange capacity are two measures of the number
of exchangeable cations in the soil. If the amount of exchangeable cations in the soil is
high, the soil more readily retains soluble salts. Thus, clay soils retain salts and drain
more slowly than sandy soils due to their low saturated hydraulic conductivity and
higher cation exchange capacity.
Evaluation Criteria
Understanding the current salinization stage of the land is an essential first step toward
addressing negative salt impacts. This soil salinization manual divides salinization into
six stages, ranging from non-impacted land to chronic surface water. Several relatively
simple tests can be done to determine the current soil salinity stage. State government
and university laboratories, listed in Appendix IV, can perform these tests. Check with
the local laboratory to see if there is a testing fee.
The physical, chemical, and hydraulic properties of coastal soils determine their ability
to retain salts when exposed to saltwater inundation. Criteria have been identified by
the U.S. Department of Agriculture (USDA) Natural Resources Conservation Service
9
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
(NRCS) to evaluate the potential of soils to retain salts based on their properties and
characteristics. The evaluation criteria are:
• 1:5 Electrical Conductivity (EC 1:5)—Test that measures the existing
electrical conductivity of soil, which can be used to estimate the soil’s
current salt content.
• Percent Sand—Soils with a higher sand content are well-drained and less
likely to retain salts.
• Depth to Water Table—A shallow water table could increase salt buildup
in the soil. A shallow water table supplies water for evaporation at the soil
surface and plant water use in the root zone through upward movement.
Dissolved salts in the groundwater, when brought upward through capillary
action, build up in the soil surface. A shallow water well can be installed
near the field to measure water table depth.
• Cation Exchange Capacity (CEC)—Soluble salts are more readily retained by
soils with higher cation exchange capacity, such as clays.
• Effective Cation Exchange Capacity—Measures the total amount of
exchangeable cations in the soil. The higher the effective CEC, the more
likely the soil will retain salts.
2.2 Soil Testing for Salt
Soil analyses are required to assess the salinity level and to identify the specific solutes
that comprise the salt in the soil. A thorough sampling of the site is recommended.
Samples from an area representing the field should be taken using a soil probe from
depths of 0–15 cm (0–6 inches) and 15–30 cm (6–12 inches). Soil experts can assist with
the interpretation of analysis results.
Quick Bioassay Method
This could be an initial test prior to sending in soil samples to a lab for analysis.
Producers can perform a simple experiment (bioassay) on their own with a small
amount of soil from affected areas before planting large acreages of forage crops,
especially ryegrass and clovers. The bioassay can help predict potential crop injury. A
bioassay does not measure the amount of salt residue present in the soil, but it may
indicate whether enough salt residue is present to injure seedlings.
To begin the bioassay procedure, take soil samples in the top 3 inches from several
locations in the field suspected of having high salt content. Mix the soil samples
together in a clean plastic pail. You will need about a quart of soil for the bioassay.
If possible, also take separate samples from fields that did not receive any saltwater
intrusion. These samples can be labeled as “check” samples. Plastic bottles and boxes,
milk cartons, and cottage cheese containers are appropriate containers in which a
bioassay can be conducted.
Punch holes in the bottom of the containers to allow water drainage. Sprinkle a small
amount of seed (about a teaspoon) in each container of soil and cover the seeds with
about ½ inch of soil. Wet the soil with water, but do not saturate it. Place the containers
in a warm location (70–75 °F) where they can receive ample sunlight. Keep the
containers moist.
10
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Within 7–10 days, injury symptoms should become apparent. Possible symptoms
include no germination, partial germination, slowed emergence, or seedlings appearing
to be dried out. It is a good idea to compare the germination and growth of the
seedlings in the salt-affected containers to those in the “check” containers. Although
this is not a precise experiment, it should provide an idea of how various forage species
may germinate and grow in areas affected by saltwater intrusion.
14
Salinity Survey Techniques
Measuring the electrical conductivity (EC) of the saturated extract is the standard
method of estimating soil salinity. The saturated extract is an extract from the soil
sample following saturation with water. The electrical conductivity of the soil extract
is determined in a laboratory. Some laboratories use different methods to measure
EC, so understanding the method used is essential when viewing soil analysis results.
This guide uses EC values obtained from a saturated paste extract as its standard.
The saturated paste extract may also be used to measure pH and analyze specific
solute concentrations such as sodium, magnesium, calcium, potassium (common
salt-forming cations), bicarbonate, carbonate, sulfate, chloride, and nitrate (common
salt-forming anions).
Soil analysis should also be performed to understand the sodicity of the soil.
Differentiating between saline and sodic soils is essential because this guide addresses
saline, not sodic soils. Sodicity is the accumulation of sodium salts specifically.
Sodium salts deteriorate soil structure and create waterlogged conditions. The level of
sodicity is related to the texture, cation exchange capacity, and infiltration properties
of the soil. High levels of sodicity may lead to crop failure. Agronomic consultants
and extension agents can assist with soil testing and understanding testing results.
Soil management and the potential amendment recommendations will depend on the
results of soil analysis. Soil analysis should include soluble salts, sodium levels, EC, ESP
(exchangeable sodium percentage), pH, and texture.
Salts can accumulate at different levels of the soil profile. An analysis of individual
samples collected from each soil horizon will provide information about the chemical
differences among soil horizons. Sampling each horizon is different from the 0–15
cm and 15–30 cm samples previously mentioned. When horizon-level soil samples
are collected, they should not contaminate samples from other depths. The samples
at each depth should be crumbled, air-dried, thoroughly mixed, and placed in labeled
containers. Labels must include the date, upper and lower profile depths of the sample,
and site name and location. The soil surface conditions, crop appearance, crop history,
yield, and next crop should also be noted for each sample site. Care should be used to
prevent contamination of the samples, including keeping them dry, and they should
be sent to the same laboratory for analysis to reduce laboratory bias errors. Soil testing
laboratories for Southeastern States are in Appendix IV.
Soil testing laboratories analyze a small soil volume to generate management
recommendations for the land manager/applicant. The land manager should try to
collect samples that adequately represent the desired total land area. However, many
agricultural fields display substantial variation in soil texture, topography, and land-
use history. The number of cores needed to reduce variation within the sample varies
with the represented area size. Many agencies and university extension services
recommend a minimum of 10 cores per sample to as high as 20 cores per sample (each
sample represents one soil horizon/core). NRCS recommends that one composite sample
11
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
(a mix of the samples collected from the same soil profile depth across the cores) per
20 acres or less is sufficient for testing in uniform fields. In smaller fields, one sample
every 5 acres is recommended. Unique areas such as low spots, contour strips, and
visible salinity stress areas should be sampled separately.
The potential for a soil to retain salts is dependent on the soil’s electrical conductivity,
total dissolved solids, soil pH, water table depth, and cation exchange capacity. Soil
should be tested for these parameters in an assessment of the soil’s condition. The
parameter terms are described below.
• Electrical conductivity (EC) is a measure of the electrical current conducted
by a saturated soil extract at a specific temperature. A higher amount of
salts in the solution increases the EC and subsequent toxicity to plants.
Electrical conductivity measures the overall water-soluble salts but does not
differentiate between the types of salts. EC units of measure are decisiemens
per meter (dS m
-1
) and millimhos per centimeter (mmhos cm
-1
), which are
equivalent (1 dS m
-1
= 1 mmhos cm
-1
). In this guide, EC is used to define
the stages of salinization. Measurements of EC are used to determine
approximate crop yield reductions due to salinity.
• Total dissolved solids (TDS) are measured by evaporating a liquid solvent
and measuring the mass of the residues. TDS is an alternative way to
measure salts in a solution but contains similar information to EC. An
approximate TDS can be estimated by multiplying the EC (dS m
-1
) of
moderately saline samples by 640 or the EC of very saline samples by 800.
The units for TDS are milligrams per liter (mg l
-1
) or parts per million (ppm),
which are equivalent.
• Soil pH is a measure of the hydrogen ion concentration in soil solution. The
soil pH scale ranges from 0 to 14: pH 7 is neutral, pH <7 is acidic, and pH
>7 is alkaline or basic. Many arable soils have a pH in the range of 6.0–7.0.
Soil pH affects soluble salts because ions react differently at varying pH
levels. Therefore, soil pH is often included in soil salinity evaluations and
discussions. Soluble salts also impact the soil pH, and pH is a valuable soil
measure without being a direct measure of salinity. Changes in soil pH
bring about changes in plant nutrient availability because microbial activity
levels respond to soil pH levels. As soil pH increases, the following elements
become limiting: iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), cobalt
(Co), phosphorus (P), and boron (B).
• Water table depth (WTD) is the depth below the soil surface where the
soil saturated zone is located. The water table depth can be measured by
installing a monitoring well and using a water level meter. If the water
table is often within 30 cm (11.81 inches) of the soil surface, dissolved
salts in the saturated zone can move upward into the root zone through
capillary action and evaporation from the soil surface, thus increasing the
salts and salinity of the soil.
• Cation Exchange Capacity (CEC) is the total capacity of a soil to contain
exchangeable cations. CEC is usually measured on microscopic scales such as
soil particles smaller than 2 mm (0.08 inches). CEC is a measure of the soil’s
negatively charged particles to attract and retain positively charged ions. Soil
with a high CEC can retain a higher amount of salts and fertilizer nutrients.
12
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Soil Potential Rating Classes
After soils have been tested using the methods outlined above, the data should
be plotted on a property map to approximate where soil salinity is an issue. The
determination of the severity of salt retention potential can be categorized using the
guidelines outlined in tables 3 and 4.
The likelihood of soils to retain salt from coastal saltwater inundation is defined in
rating classes from very low to high potential. The rating is determined by taking the
average of the rating for each criterion. Table 4 can be used to find the salinity class for
each of the evaluation criteria.
Table 3—The interaction of soil texture and EC in determining salinity class
15
Degree of Salinity (salinity classes)
Texture Non-saline Slightly saline Moderately saline Strongly saline Very saline
EC
1:1
method (dS m
-1
)
Course to loamy sand 0–1.1 1.2–2.4 2.5–4.4 4.5–8.9 >8.9
Loamy fine sand to loam 0–1.2 1.3–2.4 2.5–4.7 4.8–9.4 >9.4
Silt loam to clay loam 0–1.3 1.4–2.5 2.6–5.0 5.1–10.0 >10.0
Silty clay loam to clay 0–1.4 1.5–2.8 2.9–5.7 5.8–11.4 >11.4
EC
1:5
method (dS m
-1
)
Sand 85–100% <0.05 0.05–0.15 0.15–0.3 0.3–0.9 >9.0
Sand 75–85% <0.1 0.1–0.2 0.2–0.5 0.5–1.3 >1.3
Sand 60–75% <0.15 0.15–0.3 0.3–1.0 1.0–1.65 >1.0
Sand <55% <0.2 0.2–0.35 0.35–1.5 1.5–2.0 >2.0
EC
e
method (dS m
–1
)
All textures 0–2.0 2.1–4.0 4.1–8.0 8.1–16.0 >16
Table 4—Soil factors used in determining potential soil salt retention
15
Low Potential Moderate Potential High Potential
Depth to Water Table
centimeters, (inches)
>152.4
(60)
>50.8 to 152.4
(20 to 60)
50.8
(20) or less
Depth to Restrictive Layer
centimeters, (inches)
<50.8
(20)
50.8 to 152.4
(20 to 60)
>152.4
(60)
Cation Exchange Capacity
milliequivalents per 100 grams
<3 3 to 5 >5
Eective Cation Exchange Capacity
milliequivalents per 100 grams
<3 3 to 5 >5
Soil Organic Matter
percent
<2 2 to 5 >5
Slope
percent
>15 8 to 15 <8
Saturated Hydraulic Conductivity
micrometers (inches) per second
>40.0
(0.0016)
10.0 to 40.0
(0.00039 to 0.0016)
<10.0
(0.00039)
Cation Exchange Capacity—weighted average from 0 to 12 inches from the soil surface
Eective Cation Exchange Capacity—weighted average from 0 to 12 inches from the soil surface
Soil Organic Matter—weighted average from 0 to 12 inches from the soil surface
Saturated Hydraulic Conductivity—weighted average from 0 to 60 inches from the soil surface
13
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Soil Rating Definitions
• High Potential: Soils in this rating class have the most characteristics for salt
retention due to coastal saltwater inundation. Terrestrial soils that already
contain ocean-derived salts and have a 1:5 electrical conductivity present in
the National Soils Inventory Database (NASIS) are rated high potential.
• Moderately High Potential: Soils in this rating class have a higher number
of soil properties and characteristics for salt retention than do moderate
potential soils but lower than high potential soils.
• Moderate Potential: Soils in this rating class have a higher number of soil
properties and characteristics for salt retention than low potential soils but
lower than moderately high soils.
• Low Potential: Soils in this rating class have a higher number of soil
properties and characteristics for salt retention than very low potential soils
and lower than moderate soils.
• Very Low Potential: Soils in this rating class have the least number of soil
properties and characteristics for salt retention due to coastal saltwater
inundation.
2.3 Stages of Soil Salinization
Overview of Salinization
Soil salinization dynamics are site-specific to the hydrology, location, topography,
management practices, and local weather events (e.g., floods, droughts, hurricanes),
making the exact behavior of the salt impacts challenging to predict. This guide has
combined soil degrees of EC with frequency and duration of salt inundation events to
create six stages of soil salinity (fig. 5). The mitigation (if any), adaptation (if any), and
various crops yields are presented for each stage.
0–10
Stage Zero
Non-Impacted
EC = < 2 dSm
-1
Commercial
No
No
No
Stage One
Sporadic Salinity
EC = 2 < 4 dS m
-1
Commercial
Yes
Yes
No
Stage Five
Chronic Surface
Water
EC = >25 dS m
-1
Saltwater Marsh
No
No
Yes
Stage Four
High Chronic
Salinity
EC = 16 < 25 dS m
-1
Non-Commercial
No
No
Yes
Stage Three
Low Chronic
Salinity
EC = 8 < 16 dS m
-1
Commercial
No
Yes
No
Stage Two
Recurring
Episodic Salinity
EC = 4 < 8 dS m
-1
Commercial
No
Yes
No
Uses
Mitigation:
Adaptation:
Wetland Restoration/Easement:
Stages and Causes of Coastal Soil Salinity
Causes
Storm surge Sea-level rise Groundwater
pumping
Figure 5—The stages and causes of coastal soil salinity.
14
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
• Stage Zero: Non-Impacted Land—Baseline site characteristics are established
at Stage Zero. At this stage, working land productivity is not yet impacted
by salinity. However, the soil may be at risk of experiencing salinization due
to proximity to a saltwater source. Crop relative yield is 100 percent of the
possible yield without salinity stress, though crop yield remains subject to
other stress factors (e.g., insects, disease, drought).
• Stage One: Sporadic Salinity—Stage One salinity soil is characterized as
having sporadic, episodic salinity events. Initial salinity levels can be high
or low depending on the soil conditions before and after the saltwater event.
Some sites in this stage can recover from salinization events.
• Stage Two: Recurring Episodic Salinity—Stage Two salinity soil is
characterized by having recurring episodic events. Salinization events occur
so frequently that the site cannot sustain crops with low salinity tolerance
thresholds. The soil salinization events occur at intervals that do not allow
enough time for soil salinity levels to return to a non-saline state.
• Stage Three: Low Chronic Salinity—Stage Three salinity soil is
characterized by a sustained or increasing level of soil salinity (as measured
by EC) at a stressful level to most crops. The rate of soil salinity increase is
likely to be slow and gradual (e.g., sea-level rise). Forest crops will no longer
be productive. This is the last salinization stage (except for cotton) where
commercial agricultural productivity can occur. If soil is in Stage Three, the
landowner should start planning for the possibility of converting their land
into a conservation easement or other non-commercial use.
• Stage Four: High Chronic Salinity—Stage Four salinity soil productivity
is no longer profitable for the cultivation of commercial crops due to high
salinity levels. Water levels are high, and areas of standing water emerge.
Wetland and salt-tolerant plant species begin to colonize affected areas. The
land would best be suited for use as a conservation easement.
• Stage Five: Chronic Surface Water—Stage Five salinity soils have converted
to a saltmarsh, with high salinity levels and some open water. The area is
regularly flooded by tides. The best use of this land would be for wildlife
habitat and inland protection.
Soil Salinity Stage Progression
The stages of soil salinization do not necessarily progress in order. Soil salinity can
increase or decrease depending on site characteristics and interactions with salinization
events. For example, a specific site could experience recurring episodic salinity events
(Stage Two) for some time. However, if the events were to stop, the land could recover
to the point of moving back to Stage One if conditions such as drainage and freshwater
input were favorable.
In contrast, an area could be salinized to the point of Stage Four with its first salinity
event and never recover. Unfavorable conditions such as poor drainage and low
freshwater input could impede site recovery from a storm surge with a very high salt
input (e.g., brackish water with an EC = 25 dS m
-1
). These stages are discussed in more
detail in the following chapters and outlined in figure 5.
15
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Soil Health Conservation Practices for Maintaining Cropland Resiliency to Salinization
Healthy soil will help improve crop productivity, especially under stressors such as
salinity and drought. The primary way to achieve good soil health is by utilizing four
fundamental management principles:
• Minimize soil disturbance. Minimize tillage or use no-till if the soil is
well-drained. These practices help slow/reverse soil carbon losses (improve
carbon sequestration), stabilize soil aggregates for improved infiltration, and
promote biological activity.
• Maximize soil cover. Crop residue, mulch, and/or compost protect the soil
surface from wind and water erosion forces. Organic residues on the surface
also help conserve water for plant consumption and reduce soil temperatures
at the surface.
• Maximize the biodiversity of plant species. Plant diverse crop rotations
when possible. Different plant species are associated with distinct soil
microbial communities. Aboveground, diversity can help improve soil
organic matter, promote aggregate stability for increased water infiltration,
and alleviate compaction.
• Maximize the presence of living roots in the soil. Living plant roots
exude organic compounds that feed soil microbes and help bind soil
particles together. Plant roots are also involved in complex biochemical
communication with soil microbes whereby beneficial organisms are
recruited, and pathogenic microorganisms are deterred. These combinations
of factors create a healthier soil microbial population.
Each of these management principles are described separately but can be combined
and form the basis of an Integrated Soil Health Management System (USDA-NRCS
Soil Health Technical Note 450-05).
16
These principles can and should be applied,
if possible, no matter what stage of salinity is occurring as they promote crop
productivity. Their importance is amplified as stages of salinity increase.
Applying Appropriate Conservation Practices
The USDA NRCS identifies conservation practices that promote soil health (table 5).
Appropriately selected annual cover crops can be planted to mitigate short term or
episodic saline flooding events. However, perennial plant species used in practices
such as Forage/Biomass Planting (Practice 512)
17
and Conservation Cover (Practice
327)
17
can be used to achieve more long term soil health benefits. An index of national
conservation practices
17
can be found under technical resources on the NRCS website.
Table 5—Conservation practices that can be used in a soil health management system to help achieve
improved soil health
Soil Health
Principle
Conservation
Cover
(327)
Conservation
Crop
Rotation
(328)
Cover
Crop
(340)
Forage &
Biomass
Planting
(512)
Pest Mgmt.
Conservation
System
(595)
Mulching
(484)
Nutrient
Mgmt.
(590)
Prescribed
Grazing
(528)
Residue
& Tillage
Mgmt.
(329/345)
Minimize Soil
Disturbance
✓ ✓ ✓ ✓ ✓ ✓
Maximize Soil
Cover
✓ ✓ ✓ ✓ ✓ ✓
Maximize
Biodiversity
✓ ✓ ✓ ✓ ✓
Maximize
Living Roots
✓ ✓ ✓ ✓ ✓
Source: USDA-NRCS Soil Health Technical Note 450-05.
16
16
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Zero
CHAPTER 3
Stage Zero:
Non-Impacted Uplands in Proximity
to Impacted Lands
3.1 General Discussion
Baseline site characteristics are established at Stage Zero. At this stage, working
land productivity is not yet impacted by salinity. However, the soil may be at risk of
experiencing salinization due to proximity to a saltwater source. Crop relative yield
is 100 percent of the possible yield without salinity stress, though crop yield remains
subject to other stress factors (e.g., insects, disease, drought).
Setting a baseline is essential when determining how salinization can impact working
lands. The relative impact of saltwater can be more accurately assessed once the
baseline productivity is known. Non-impacted soils in proximity to affected lands
are likely susceptible to salinization. The amount of time taken for these lands to
experience salinity increases depends on the site conditions and salinization drivers
discussed in the introduction. Soils with an electrical conductivity between 0 and 2 dS
m
-1
are considered non-saline. Salts can be flushed from the land if soil is well-drained,
and the timing and amount of rainfall is sufficient to flush the soils. Both the lack of
drainage and freshwater input contribute to salinity accumulation in the soil.
3.2 Productivity and Economic Limitations
There will be a negligible impact on crop productivity during Stage Zero, even though
there may be some small increases in salinity. Traditional crops can be cultivated in a
business-as-usual approach. However, monitoring of soil conditions is advised for early
detection of soil salinity change.
3.3 Mitigation and Adaptation Measures
No specific salinization related mitigation or adaptation measures are needed in
Stage Zero because natural flushing will take care of any salt in the system. However,
employing some basic soil health and conservation practices is advisable, regardless of
the salinization stage, to help the cropland become more resilient to changing climatic
conditions.
3.4 Environmental Impacts
Soil salinization can have direct impacts through the accumulation of salt in the
soil. There can also be indirect impacts on the ecosystem as the non-salinized soils
become more susceptible to other disturbances. Additionally, increased stress on the
impacted land can spill over onto adjacent, non-salinized areas. For example, non-
impacted lands have increased susceptibility to common reed (Phragmites australis)
when the site is near other lands that are salinized. Common reed spread is associated
with agriculture and is a problem in the coastal region of the Eastern United States.
17
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Zero
Common reed is an invasive species
that negatively impacts native
biodiversity and habitat. However,
common reed can have benefits such
as nutrient remediation and shoreline
stabilization.
18
(See photo left.)
The best way to prevent or minimize
the invasion of common reed into
a cropped field and to protect water
quality is to establish a dense
vegetative cover at the edge of the
field. Useful edge-of-field NRCS
practices to reduce invasion risks
include Field Border (386), Filter
Strip (393), Riparian Herbaceous
Cover (390), and Riparian Forest
Buffer (391).
17
Additional field scale practices may also be implemented, such as Forage
and Biomass Planting (512) and Conservation Cover (327).
17
If a field is adjacent to an
eroding shoreline, the Streambank and Shoreline Protection (580)
17
may be needed.
The practices or combination of practices recommended will vary depending on site
conditions, resource concerns to be addressed, and the producer’s land management
goals.
3.5 Probable Outcomes for Stage Zero Land
Stage Zero salinized soil would likely remain in stage zero classification indefinitely
if climate change was not increasing sea levels. However, climate change is expected
to cause an average increase in a sea-level rise of 45.4 cm (17.9 inches) across the U.S.
Southeast by the year 2050.
19
Beyond this time, studies suggest that sea-level rise could
reach up to 90 cm (35.4 inches) by 2100. In the Mid- and Upper Atlantic, 90 cm of sea-
level rise would inundate over 2,600 km
2
(642,000 acres). Along the entire eastern U.S.
coastline, from the Atlantic Ocean to the Gulf of Mexico, over 87,000 km
2
(21 million
acres) could be at risk of being inundated from storm surges by 2100.
20
The NOAA Sea
Level Rise Viewer provides the location-specific prediction of sea-level rise. Other tools
and resources are presented in Appendix I of this guide.
In addition to sea-level rise, extreme weather events such as droughts and storms are
expected to increase in frequency and intensity. Recent decades have seen an increase
in tropical cyclone activity in the Atlantic.
21
Increased temperatures and changing
precipitation regimes are expected to lead to more drought.
22
Wet areas are expected
to become wetter, and dry areas are expected to become drier. For coastal areas, less
freshwater may be available for saltwater intrusion irrigation mitigation. The salinity
of tidal rivers can increase during low flow periods.
23
Predicting coastal soil response
to climate change is difficult due to the dynamic and interactive nature of saltwater
intrusion and land. Although currently not impacted, Stage Zero lands in proximity to
Stage One areas should be closely monitored for changing conditions.
Abandoned cropland encourages the Phragmites invasion. (Photo
by Chris Miller, USDA-NRCS)
18
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage One
CHAPTER 4
Stage One:
Commercial Upland Introduction of Salinity
Stage One salinity soils are the first to show symptoms of saltwater intrusion.
The impacts may be subtle, and the producer may not notice the slight decrease in
productivity relative to yearly production variability. However, early intervention can
significantly improve the resiliency of the soil to additional salinization. This chapter
will review how to identify, mitigate, and adapt to soil salinization’s emerging problem.
Stage One Characteristics
Stage One soil salinization is characterized by low levels of salinity. In this stage, mitigation
measures may be possible to improve soil salinity levels. Stage One salinity soil is
characterized as having sporadic, episodic salinity events. Initial salinity levels can be high
or low depending on the soil conditions before and after the saltwater event. Some sites in
this stage can recover from salinization events.
EC: detectable
2<4 dS m
-1
Crop options: many
Numerous crops have a salinity threshold to produce 100 percent relative yield in this stage,
though more sensitive plants begin to have reductions in yield due to salinity.
Practically treatable? Yes
4.1 General Discussion
The initial introduction of salinity could come from salt spray from ocean water,
high tides such as king [i.e., exceptionally large (perigean spring)] tides, storm-
driven flooding, saltwater intrusion during a drought, or saline irrigation water. Soil
salinity levels could be relatively high due to an extreme event. However, if saltwater
is introduced due to a chronic condition such as the slow movement of saltwater
intrusion due to sea-level rise, the soil salinity level is likely to start at a low level and
gradually increase at a slow rate. In the latter case, the initial introduction of salinity
will be at low levels. Therefore, low lying areas are the first to be exposed to salinity.
In agriculture, heavy equipment tracks can leave depressions in fields where salt can
pool after the initial stages of saltwater intrusion. Monitor these areas for early signs of
soil salinization.
19
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage One
4.2 Productivity/Economic Limitations
The initial impacts on crop productivity from salt to the soil depend on saline
condition, salinity level, and exposure. Salinity impacts crop yield when soil salt levels
reach or exceed the tolerance threshold specific to the crop (table 1, ch. 1). The crop yield
decreases as salinity increases above a crop salt tolerance threshold (table 6). Crop yield
decline due to salinity can be estimated as described in Chapter 1. However, crop yield
is a product of multiple interacting factors, such as climate, water availability, nutrient
availability, pests and disease, and soil conditions, along with salinity. The estimates
of crop yield under various salinity levels do not account for yield reductions due to
other factors and are estimated as if other conditions are ideal (e.g., no yield loss due to
insects, disease, drought).
Table 6—Percent crop yield at the low and high limits of Stage One soil salinization for row
crops, vegetables, and fruits at 2 dS m
-1
to 4 dS m
-1
Crop Botanical name % Yield at 2 dS m
-1
% Yield at 4 dS m
-1
Row Crops
Corn
Zea mays
99 84
Flax
Linum usitatissimum
96 72
Sugarcane
Saccharum oicinarum
98 86
Potato
Solanum tuberosum
96 72
Broadbean
Vicia faba
96 77
Sweet Potato
Ipomoea batatas
95 73
Radish
Raphanus sativus
90 64
Turnip
Brassica rapa (Rapifera)
90 72
Artichoke, Jerusalem (Tabers)
Helianthus tuberosus
85 65
Bean, mung
Vigna radiata
96 54
Almond
Prunus duclis
91 53
Bean
Phaseolus vulgaris
81 43
Vegetables
Cabbage
Brassica oleracea (Capitata)
98 79
Celery
Apium graveolens
99 86
Pepper
Capsicum annuum
93 65
Lettuce
Lactuca sativa
91 65
Onion (seed)
Allium cepa
92 76
Onion (bulb)
Allium cepa
87 55
Carrot
Daucus carota
86 58
Fruits
Tomato, cherry
Lycoperscion lycopersicum- cerasiforme
97 79
Grape
Vitus vinifera
95 76
Eggplant
Solanum melongena
94 80
Muskmelon
Cucumis melo
92 75
Grapefruit
Citrus x paradisi
97 70
Peach
Prunus persica
94 52
Orange
Citrus sinensis
95 69
Lemon
Citrus limon
94 68
Blackberry
Rubus macropetalus
89 45
Boysenberry
Rubus ursinus
89 45
Strawberry
Fragaria x ananassa
67 1
20
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage One
Rates of soil recovery from saltwater events will be prolonged if hydrological features
(e.g., roads, levees, or flood gates) trap saline water inland. Salinity can also cause the
release of nutrients (e.g., nitrogen and phosphorous) and export them from the soil.
24
Loss of nutrients may increase the amount of fertilizer required to produce crops.
Increases in sodium due to increases in salinity may bring about clay dispersion,
change the soil structure, and lead to poor drainage, severely reducing crop yield.
Salinization allows the invasion of unwanted opportunistic vegetation species to
colonize existing plant communities. As salinity is introduced, a decrease in plant
community diversity is likely to be observed. Plant communities that are not adapted to
wet and/or saline soils may be vulnerable to marsh migration.
25
The control of invasive
species within crop fields will require more control measures as salinity increases,
which will reduce the total profit from the crop.
Forestry
Forest stands are likely to recover from a single salinization event but may be impacted
in the short term. At low salinity (i.e., 2–4 dS m
-1
), seedling growth of trees such as
loblolly and pond pine may be unaffected.
26
However, during a storm, inundation by
brackish water can reduce trees’ capacity to move water, leading to immediate damage
to the forest. High salinity (i.e., >16 dS m
-1
)
27
stress in trees can reduce sap flow (the
movement of fluid in the tree), slow basal area and tree height growth, and lead to
death, sometimes from a single storm event. Mature trees are more likely to be resilient
to soil salinity than young regenerating trees. Soils can recover from individual events
of Stage One salinization, especially when the event is followed by rainfall. However,
a storm surge followed by drought may amplify the impact of salinity stress on trees
as a lack of freshwater can concentrate the salinity in the soil. Tree mortality can be
delayed after experiencing flooding and salinity from a storm surge, so post-hurricane
management should consider the level of salinization. If the salinization level is high
and salinity enters the groundwater near the rooting zone, the soil could take years to
recover and cause long-term tree damage. Seedlings such as green ash, water tupelo,
and bald cypress may recover from exposure to salinity as high as 16 dS m
-1
. However,
growth rates could initially be reduced. Seedlings could die in 2–6 weeks if exposed
to saline water >25 dS m
-1
for 48 hours.
28
Revegetation after saltwater intrusion will
depend on returning the soil salinity to lower levels. High elevation plays a significant
role in the recovery as these areas are more likely to drain salt out of the soil during
precipitation events. Conversely, low-elevation sites do not permit the removal of salt
from the soil. However, during short-term, lower salinization events, trees are likely to
improve.
4.3 Environmental Impacts
Saltwater interaction with soils can release nutrients from fertilizers, leading to
nitrogen and phosphorus export. Nitrogen and phosphorus export can lead to harmful
algal blooms that later die and decompose by bacteria that then degrade the habitat
for animals and cause other harmful coastal ecosystem effects. The nutrient release
rate will depend on sea-level rise, salinity level, storms, drought, connectivity to water
bodies, and land-use decisions, including fertilizer application.
21
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage One
4.4 Mitigation Measures
Mitigation measures can be either shorter term or annual practices that can be
implemented in the early stages of soil salinization. The usefulness of these techniques
depends on salinization’s cause, extent, and depth of the water table. If the groundwater
table is shallow, many mitigation practices are not possible because the soil is too wet,
and the water will not drain. With sea-level rise, the water table will continue to get
closer to the surface, and mitigation will become less and less of an option. Soil salinity
levels are more likely to decline from infrequent salinization events (one every 10 years)
compared to chronic inputs of salt. If the salinity source is continuous, then adapting to
salinity will be necessary. The following mitigation strategies can be used in the early
stages of salinization, in addition to adaptation measures described in the next section
and the following chapters. [Mitigation measures are less viable options in the later
stages of salinity. Instead, adaptation practices should be used.]
• Water Control. Water control infrastructure such as flood gates, dikes,
levees, and valves can be used to prevent some saltwater intrusion.
However, these structures can also trap salinity behind them when they are
overtopped. Whether or not the water level exceeds the structure height is
determined by the water height of storm surges or high tides. Eventually,
due to sea-level rise, existing water control structures will be overtopped
more easily. Refer to NRCS Conservation Practice Standard 356 (Dike).
17
Commonly associated practices include: Structure for Water Control (587),
Irrigation Water Management (449), Wildlife Habitat Management (644),
and Wetland Creation (658).
17
However, structure construction could hinder
conversion options to a conservation easement when the productivity level
decreases beyond economic viability. Additional information on Wetland
Reserve Easements and Conservation Compliance Determinations is
available through the Natural Resources Conservation Service.
• Irrigation Methods. Leaching soils with freshwater can reduce salinity in
well-drained soils and conditions where the groundwater table is not close
to the surface. If leaching is suitable, irrigation with 6 inches of freshwater
can reduce salinity by up to 50 percent, though the leaching process can be
slow and take several years. As sea levels rise, leaching will become less of a
viable option. Soil amendments such as gypsum may increase the removal
of soluble salts when combined with freshwater irrigation. Gypsum is high
in calcium and may react with the soil’s exchange site to release sodium.
The composition of soluble salts in the soil, sodium, EC, ESP, pH, texture,
and fertility will influence whether gypsum use is recommended. Soil
analysis laboratories can provide a specific recommendation for using soil
amendments at a particular location. For more information, see the NRCS
Conservation Practice Standard, Amending Soil Properties with Gypsum
Products Code 333.
17
• Soil Health. Utilize soil health management techniques described in Stage
Zero by employing no-till or minimum tillage, improving year-round
cover, adding organic amendments, and diversifying crop rotations.
Refer to Conservation Practice Standards 329/345,
17
Residue and Tillage
management, for more information.
22
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage One
• Helpful Strategies. Additional strategies include shifting planting dates to
avoid field operations during wet/flooded conditions, controlling/limiting
heavy machinery traffic to minimize soil compaction, and land leveling or
subsurface drainage if hydrologic conditions allow. In more salinized fields,
leave a field fallow for a season with weeds controlled through herbicides or
shallow mechanical tillage (discing). Leaving the field fallow for a season
will reduce plant water use and promote salt leaching deeper into the soil
profile through increased drainage. Cover crops such as barley and vetch
also promote salt leaching in irrigated systems. Cover crops may have
the added benefit of reducing soil salt accumulation at the next cash crop
planting.
29
Planting crops on shallow ridges or raised beds will keep plant
roots above the more saline soil zone. In some exceptional circumstances,
dredge or spoil material may be available for land application to add
elevation to low lying fields. Refer to NRCS conservation practice standard
Spoil Spreading, Code 572
17
to adequately spread this material.
• Deep Tillage and Organic Amendments. Deep tillage (plowing), along
with soil amendments, may be a viable method to reduce salts if salt is
only concentrated in the upper depth (5–10 cm or 2–4 inches) of the soil.
For example, organic amendments such as mulch, leaf compost, or biochar
can be incorporated into the soil to reduce the salt concentration. These
amendments help improve soil organic carbon and “dilute” the salt effect
by reducing sodium on a large percentage of the soil exchange sites (clays
and silts). However, deep tillage does not work in shallow groundwater
tables. Refer to NRCS Conservation Practice Standard 324, Deep Tillage.
17
As
climate change continues to raise groundwater tables in coastal areas, this
will become increasingly less useful.
4.5 Adaptation Measures
Adaptation measures are long-term techniques that adjust business-as-usual
agricultural practices to remain productive. Examples include crop-pasture rotation,
grass crop rotation, cover cropping, and silvopasture. Crop-pasture rotation is an
adaptation strategy to continue profitably managing the land. Grass crop rotation
with row crop systems can reduce runoff, erosion rates, and environmental impacts
in non-salinized lands. Cover cropping provides many benefits, including erosion
management, increased soil organic carbon sequestration, and improved soil physical,
chemical, and biological characteristics. The integration of livestock with these systems
increases the net return, though integration demands more skill and knowledge
because a two-crop system is more complex.
30
The NRCS employs a host of conservation practice standards and specifications to plan
best management practices on farms to solve various natural resource problems. These
practice standards in the Field Office Technical Guide (FOTG) are updated and revised
periodically with new vegetative planting and engineering design recommendations.
Many of the vegetation conservation practices
17
such as Riparian Herbaceous Buffers
(390), Filter Strips (393), Field Border (386), Streambank and Shoreline Protection (580),
Cover Crop (340), Conservation Cover (327), and Forage and Biomass Planting (512)
are useful practices in helping a farmer buffer crop fields from coastal flood damage
and salinization problems. Plant species recommended to be used in these practices
provide water quality improvement by plant nutrient removal from potential soil legacy
23
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage One
nutrients released by saltwater flooding. Contact the county NRCS Field Office for
information on conservation practices and plant recommendations given specific soils
and site conditions.
Producers should consider crop insurance programs regardless of the crops that are
planted. The USDA Noninsured Crop Disaster Assistance Program (NAP) provides
financial assistance to producers that are not able to be insured when low yields, loss
of inventory, or prevented planting occur due to natural disasters. Consult the local
extension agent regarding insurance program options.
Changing Planted Species and Crop Rotations
During the early stages of salinization, switching crops is not required but could
become a viable option as salinization continues. If salinization occurs due to
infrequent weather events, continuing business as usual agricultural practices could
make economic sense. If salinity levels are steadily increasing, converting to more
salt-tolerant crops may make more economic sense. The salinity tolerance of traditional
crops is shown in table 1. Traditional crops with higher thresholds for salinity should
be considered when salt initially appears in the soil. Switching to alternative crops
could also be done at this point, but cultivating traditional crops may be best to
continue while possible. Alternative crops are described more fully in Chapters 5 and 6.
Cover crops are useful for erosion control, while salts are leaching from the soil. If the
salinity is in the top 5–7 cm (2–3 inches) of the soil profile, deep plowing combined
with cover crops such as barley, tall fescue, or perennial ryegrass can assist with salt
leaching. A permanent vegetative crop established before the salinization occurred
can be left in place and combined with gypsum application where applicable, and
freshwater irrigation can be used to reduce salinity. The salt content in most soils in
Stage One will recover in 6–12 months.
Table 1 includes the salinity and electrical conductivity (EC) thresholds for salt-tolerant
plants. The EC threshold is the maximum value that does not reduce relative yield
below the species’ yield under non-saline conditions. The reduction of yield due to an
increase of one decisiemen EC (expressed as a slope) is also factored into determining
a species’ salt tolerance. Species with a steep slope have a high reduction in yield as EC
increases. Therefore, species with a steep yield loss slope are less salt-tolerant than a
crop with a low slope. If the initial salinity levels are low, there could be few noticeable
effects, and salt-sensitive plant species may still produce acceptable yields. However, as
the salinity levels increase, more salt-tolerant varieties of plants will remain resilient to
unpredictable climate conditions and weather events.
4.6 Probable Outcomes
Coastal areas will continue to experience impacts from salinity due to natural
climate-related drivers. The hydrology, soil type, connectivity to saltwater intrusion,
and proximity to the ocean of a site will determine the rate at which soil experiences
salinization, combined with unpredictable climate-driven events. Saltwater
intrusion, along with rising sea levels and increasing drought severity, is expected
to impact a growing extent on the Southeast coast. Continuous saltwater intrusion
combined with storms stress upland ecosystems and convert them to saline wetlands
or emergent marsh.
4
24
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Two
CHAPTER 5
Stage Two:
Commercial Upland, Recurring
Episodic Salinization
As salt concentrations continue to increase in the soil, productivity reductions will be
more pronounced at this stage. Additionally, the salt crust may be more noticeable on
the soil surface. These soils are still productive, but there are fewer crop choices that
will tolerate elevated salt levels. This chapter discusses these options.
Stage Two Characteristics
Stage Two soil salinization is characterized by more frequent episodic salinity events.
Salinity levels in this stage increase and exhibit less recovery. The more frequent
occurrence of salinity events provides less time for recovery between events, and salinity
levels increase. Salinization events occur so frequently that the site cannot sustain crops
with low salinity tolerance thresholds. The soil salinization events occur at intervals that do
not allow enough time for soil salinity levels to return to a non-saline state.
EC: detectable
4<8 dS m
-1
Crop options: some
Some crops (n=14) are available that have a salinity tolerance threshold to produce 100
percent relative yield at this stage. However, at the higher end of salinity stage, few crops
produce >70 percent yield (n=11).
Practically treatable? No
5.1 General Discussion
Recurring episodic salinization events will build up soil salinity and push systems past
their ability to recover. In Stage Two soil salinization, electrical conductivity values
range from 4 to 8 dS m
-1
. However, 4–8 dS m
-1
electrical conductivity can also briefly
occur in other stages. In Stage Two, increasing pressure from natural climate-related
drivers and decreasing time between events leaves less time for recovery and increases
soil salinity. The increase in salinity could happen gradually over a long period, or an
increase could happen rapidly due to an extreme event.
5.2 Productivity/Economic Limitations
Under salt stress, wetland forest production is reduced, and tree seedling mortality
occurs.
10
Agricultural crop yields also decline with increasing salinity levels, though
they have varying thresholds. These thresholds determine the rate of yield decline
(tables 7 and 8).
25
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Two
Table 7—Percent crop yield at the low and high limits of Stage Two soil salinization for row crops,
vegetables, fruits, and forage/cover crops/erosion control at 4 dS m
-1
to 8 dS m
-1
Crop Botanical name % Yield at 4 dS m
-1
% Yield at 8 dS m
-1
Row Crops
Barley Hordeum vulgare 100 100
Sugar beet/Red beet Beta vulgaris 100 94
Cotton Gossypium hirsutum 100 98
Triticale X Triticosecale 100 95
Wheat, durum Triticum turgidum 100 92
Sorghum Sorghum bicolor 100 81
Artichoke Cynara scolymus 100 78
Wheat Triticum aestivum 100 95
Soybean Glycine max 100 40
Garlic Allium sativum 99 41
Quinoa Chenopodium quinoa willd 98 91
Alfalfa Medicago sativa 85 56
Corn Zea mays 84 54
Flax Linum usitatissimum 72 24
Sugarcane Saccharum oicinarum 86 63
Potato Solanum tuberosum 72 24
Broadbean Vicia faba 77 39
Sweet Potato Ipomoea batatas 73 29
Radish Raphanus sativus 64 12
Turnip Brassica rapa (Rapifera) 72 36
Artichoke, Jerusalem (Tabers) Helianthus tuberosus 65 27
Rice, paddy Oryza sativa 88 40
Vegetables
Asparagus Asparagus oicinalis 100 92
Squash, zucchini Cucurbita pepo var. cylindrica 100 66
Pea Pisum sativum 94 51
Squash, scallop Cucurbita pepo var. clypeata 87 23
Broccoli Brassica oleracea (Botrytis) 81 18
Cucumber Cucumis sativas 81 29
Spinach Spinacia oleracea 85 54
Cabbage Brassica oleracea (Capitata) 79 40
Celery Apium graveolens 86 62
Pepper Capsicum annuum 65 9
Lettuce Lactuca sativa 65 13
Onion (seed) Allium cepa 76 44
Carrot Daucus carota 58 2
Fruits
Guava Psidium guajava 100 68
Tomato Lycoperscion lycopersicum 85 46
Tomato, cherry Lycoperscion lycopersicum- cerasiforme 79 43
Grape Vitus vinifera 76 38
Eggplant Solanum melongena 80 52
Muskmelon Cucumis melo 75 41
Grapefruit Citrus x paradisi 70 16
Orange Citrus sinensis 69 16
Lemon Citrus limon 68 17
Forage/Cover Crops/Erosion Control
Ryegrass, perennial Lolium perenne 100 81
Cowpea Vigna unguiculata 100 63
Sudangrass Sorghum sudanense 91 55
Vetch, common Vicia sativa 89 45
Clover, berseem Trifolium alexandrinum 86 63
Clover, alsike Trifolium hybridum 70 22
Foxtail, meadow Alopecurus pratensis 76 38
Clover, red Trifolium pratense 70 22
Clover, ladino/white Trifolium repens 70 22
Orchardgrass Dactylis glomerata 85 60
Species with zero yield at the high end Stage Two salinity include: almond, bean, bean (mung), blackberry, boysenberry, bnion (bulb), beach, beanut, blum (prune),
strawberry
26
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Two
Forestry
The moderate levels of salinity in Stage Two are likely to negatively impact forest
growth and productivity. Signs of salinity stress will begin to persist (i.e., decrease
in overall vigor, increase in insect problems, sparse crown, low growth, mortality,
short needle length in pines, small foliage in hardwoods, and overall appearance of
poor health). Forests in poor health are at a higher risk for pests and diseases. Forest
recovery between salinity events will depend on the frequency and intensity of their
reoccurrence. After an event, the forest’s health should be assessed and may need to be
harvested. In some cases, trees should be harvested before their quality deteriorates.
Once harvested, the condition of the land and options for land-use change should be
assessed. Seedlings are not adapted to continuous moderate to high salinity levels and
may have difficulty reestablishing and maintaining productivity if soil salinity remains
elevated. Production in mature forests declines with moderate to high levels of salinity.
In areas where salinization events happen often and include intense storms, tree
mortality could increase up to 85 percent with soil salinity in the 4–8 dS m
-1
range.
12
5.3 Environmental Impacts
Ecosystem carbon dynamics can change due to saltwater intrusion, meaning ecosystem
productivity and carbon storage potential can be reduced. For example, saltwater
intrusion can cause forest death, and vegetation change to shrubs and grasses. As
soils become slightly saline, forests become stressed and seedling survival declines.
Reduced seedling vigor can inhibit forest regeneration. Without regenerating, the forest
community will change to shrubs and grasses. Following forest death, salt-tolerant
species will invade. The rate of forest retreat coincides with the rate of sea-level rise.
31
5.4 Adaptation Measures
Managing the impact of saltwater intrusion will require producers to use more adaptive
and innovative agricultural practices. Producers in these impacted areas may not need
to completely abandon their affected fields if site assessment tools and appropriate
Table 8—Crops that would be suitable for growing under Stage Two soil
salinization
Common name Botanical name EC threshold (dS m
-1
)
Row Crops
Guar Cyamopsis tetragonoloba 8.8
Barley Hordeum vulgare 8.0
Cotton Gossypium hirsutum 7.7
Sugar beet/Red beet Beta vulgaris 7.0
Sorghum Sorghum bicolor 6.8
Triticale X Triticosecale 6.1
Artichoke Cynara scolymus 6.1
Wheat Triticum aestivum 6.0
Wheat, durum Triticum turgidum 5.8
Quinoa Chenopodium quinoa willd 3.0
Forage/Cover Crop/Erosion Control
Bermuda grass Cynodon dactylon 12.0
Fescue, tall Festuca arundinacea 7.0
27
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Two
conservation practices are used. However, in some cases, wetland conservation
easements may be the best option. Easements would result in previous cropland
being converted to wetlands either through natural regeneration or planned wetland
creation. The benefit to the producer would be a one-time acreage payment for the
land acquisition. The ecosystem benefit would be the additional floodwater storage
that may help protect and buffer adjacent cropland. One consideration is water control
structures. Structure construction could hinder conversion options to a conservation
easement when the productivity level decreases beyond economic viability.
Additional information on Wetland Reserve Easements and Conservation Compliance
Determinations are available through NRCS. Check with the local extension agent or
NRCS field staff for more information on conservation easements.
Agricultural practices that can manage the impacts of salinity stress include planting
more salt-tolerant crops, using crop-pasture rotation, and applying conservation
practice standards. Another alternative strategy would be growing value-added
alternative niche conservation plants. Alternative crops on these marginal lands may
provide valuable ecosystem services and potentially provide additional farm income.
The opportunity to profit from alternative crops depends on locating specialized
markets for the product. Some potential options are discussed below.
Saltmarsh Hay Production
Native salt meadow cordgrass (Spartina patens), or saltmarsh hay, was historically
harvested from natural tidal marshes and used for a wide array of applications:
bedding for horses and cattle, cattle feed, weed-free mulch (due to the inability of
seeds to germinate outside the salt environment) for nursery and vegetable production,
biodegradable packing material to ship fragile items, increased traction on roads,
protecting and curing concrete, and production of saltmarsh hay rope. However, most
of these “farmed” wetland areas on the East Coast are no longer accessible due to sea-
level rise and storm damage to dikes and levees through the years. Opportunities exist
for farmers to plant a crop of salt meadow cordgrass in the marginal, salt-impacted
transition zone between the wetland and the upland. These marginal lands were once
traditionally farmed, but they are no longer economically productive due to periodic
flooding and salt concentrations. However, they may be suitable for the production of
salt meadow cordgrass. Salt meadow cordgrass markets vary locally and may not be
applicable or profitable everywhere.
‘Flageo’, ‘Sharp’, and ‘Avalon’ are three varieties developed by the USDA-NRCS Plant
Materials Program. ‘Flageo’ is best used to stabilize high saltmarshes, interdune swales,
low coastal dunes, and highly erodible inland sites with deep sands. ‘Avalon’ is best
used for marsh habitat restoration purposes, dune stabilization and restoration projects,
and shoreline protection applications at high energy sites. ‘Sharp’, a Gulf Coast strain,
appears to produce the most biomass of the three. Further testing is being done by the
NRCS Cape May Plant Materials Center. These varieties all have some degree of natural
tolerance for saline environments and will also grow in higher elevation, sandy dune,
and shoreline sites. (See photos on the following page.)
In Delaware, annual dried biomass production ranged from 3175 kilograms (3.5 tons)/
acre to 5806 kilograms (6.4 tons)/acre in a study examining multiple harvest dates and
single harvest dates on research plots. There was no advantage of multiple harvests
during the growing season in terms of biomass production.
32
As with any farming
operation, harvesting should only be done when soil conditions are appropriate to
28
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Two
reduce compaction. Fertilization can significantly improve yields in saline soils.
Fertilizing cordgrass in a Stage One (8 ppt salinity) salt meadow can significantly
improve crop yield.
Seashore Mallow
Seashore mallow (Kosteletzkya virginica) is another plant that provides ecosystem services,
as well as potential income. Seashore mallow is a wetland species that is native to the
Mid-Atlantic and Gulf Coast States. Seashore mallow has been studied for its potential
use as an ecosystem engineering tool in the transition zone between wetland and
upland in agricultural fields experiencing saltwater flooding. Planting seashore mallow
in these riparian areas can increase organic matter in the soil, utilize nutrients coming
from upland fields, and encourage other desirable native species to volunteer while
discouraging the invasion of common reed. In addition to these ecosystem benefits,
various value-added products could potentially be marketed from seashore mallow. The
oilseed produced by the mallow has been researched as a biodiesel product. The chopped,
dormant stems of native grasses and seashore mallow have highly absorbent fibers and
show promise as poultry house bedding material and cat litter. Research has shown that
seashore mallow is more adsorbent than sawdust, which has been the poultry industry
standard for years. The use of native grass bedding also results in less footpad dermatitis
on the birds. Additionally, the chopped biomass residue is used to manufacture products
associated with the erosion control industry and in the natural gas extraction industry.
Seashore mallow can be readily seeded as well as harvested using conventional farm
equipment. (See photos below and on following page.)
lef t: Natural stand of salt meadow cordgrass. (Photo by Marilee Lovit, Go Botany); right: Harvesting salt hay. (Photo by
Joseph Smith)
Seashore mallow seeding: conventional left and no-till right. (Photos courtesy of Dr. Jack Gallagher and Dr. Denise Seliskar
of the University of Delaware)
29
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Two
Integrated Multifunctional Buers
One conservation best management practice is establishing or maintaining existing
natural buffer systems adjacent to waterways or wetlands. These buffers provide
ecosystem services for erosion control, water quality improvement, and wildlife habitat
and potentially slow the invasion of Phragmites into fields if present on the wetland
margins. Where potential markets exist, the possibility of establishing multifunctional
buffers of deep-rooted native warm-season grasses such as switchgrass (Panicum
virgatum), coastal panicgrass (Panicum amarulum), prairie cordgrass (Spartina pectinata),
Eastern gamagrass (Tripsacum dactyloides), and wetland forbs such as seashore mallow
(Kosteletzkya virginica) for biomass harvesting may be profitable as an alternative
income source. (See photos below.)
Farmers may be able to extend productivity on impacted land by planting salt-tolerant
crops. Research is being conducted to find the tolerance of crops (e.g., varieties of barley,
sorghum, soy, switchgrass) planted and harvested with equipment that farmers already
have. Conservation practices may provide protection for non-impacted areas, improve
water quality, and provide income sources.
left: Crops protected in a Maryland field with buffer planting ; right: Unprotected field with no buffer planting (right).
(Photos by Chris Miller, USDA-NRCS)
left: An established stand of seashore mallow; right: Closeup of the mallow flowers. (Photos courtesy of Dr. Jack Gallagher
and Dr. Denise Seliskar of the University of Delaware)
30
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Two
Refer to Plant Materials Technical Note # 3 Planting and Managing Switchgrass as a
Biomass Energy Crop
33
for more specific information on establishing bioenergy crops.
The ground stem can also be used in various erosion control products.
Regardless of the crops planted, landowners use insurance and disaster recovery
programs to buffer against loss. For example, the USDA Farm Service Agency
Noninsured Crop Disaster Assistance Program (NAP) provides financial assistance
to producers of crops that cannot be insured when low yields, loss of inventory, or
prevented planting occur due to natural disasters. Consult with the local extension
agent, NRCS, and FSA field offices to learn more.
5.5 Probable Outcomes
Sea-level rise will continue to bring saltwater further inland, reducing the soil’s ability
to recover and changing land to the point where salinity is well-established. Ecosystem
biogeochemistry could be influenced by processes that occur along with salinization.
Alkalinization and sulfidation occur with chronic salinization and may become
more rapid with each event. Alkalinization raises soil pH and may reduce phosphorus
availability. Sulfidation increases sulfide of soil and may produce hydrogen sulfide,
which is toxic to plants.
13
Forest and cropland will decline in productivity to the point
where adaptation measures will be required to continue keeping the land productive.
31
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Three
CHAPTER 6
Stage Three:
Commercial Upland, Well Established,
Chronic Salinization
If soil is in Stage Three, the landowner should start planning for the possibility of
converting their land into a conservation easement or other non-commercial use.
Stage Three salinized soils are at the transition from marginally productive to non-
productive. Therefore, careful soil sampling and consideration of species selection
are needed before row crops are planted. These lands are no longer suitable for tree
replanting even if a seedling would initially grow at Stage Three levels of soil salinity.
The likelihood that a seeding would reach a commercially viable sawtimber stage is
low due to the long (i.e., 25+ year) rotation length and continued sea-level rise.
Stage Three Characteristics
Stage Three sites experience chronic salinization and a steady increase in soil salinity
levels. The options for economically feasible yields are increasingly limited due to increasing
soil salinity. Stage Three salinity soil is characterized by a sustained or increasing level of
soil salinity (as measured by EC) at a stressful level to most crops. The rate of soil salinity
increase is likely to be slow and gradual (e.g., sea-level rise). Forest crops will no longer
be productive. This is the last salinization stage (except for cotton) where commercial
agricultural productivity can occur.
EC: detectable
8<16 dS m
-1
Crop options: few
At the high end of Stage Three, no crops have a salinity tolerance threshold that allows
for 100 percent relative yield, though some crops can still be cultivated at the lower end of
salinity levels.
Practically treatable? No
6.1 General Discussion
Stage Three salinization would fall under the traditional classification of “strongly
saline” soil salinity class
9
with an electrical conductivity ranging from 8 to 16 dS m
-1
.
During chronic salinization, sulfidation begins to occur. Examples of well-established
salinization can be seen in the Delmarva and North Carolina Albemarle-Pamlico
peninsulas. In these areas, saltwater intrusion causes farmland to become unprofitable
with traditional planting practices. Sea-level rise will cause further saltwater intrusion
into aquifers. Salt spray, a continuous source of salt in coastal areas, will continue, and
its reach will move farther inland as shorelines move due to sea-level rise.
32
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Three
6.2 Species Tolerance
At 8–16 dS m
-1
electrical conductivity, species with higher salt tolerance are best suited
for cultivation. However, not many plant species can tolerate waterlogged and saline
environmental conditions (table 9).
Forestry
Stage Three salinity stress makes commercial forestry no longer a viable option for
the impacted land. In Stage Three, trees exhibit a severe decrease in overall vigor,
increase in insect problems, sparse crown, inferior growth, increased mortality, short
needle length in pines, small foliage in hardwoods, and increased overall appearance
of poor health. Forestry operations in these areas are unlikely to be successful. Chronic
salinity can be identified in forests by encroaching salt-tolerant species, such as Wax
myrtle (Morella cerifera).
34
The land can be left to transition naturally into saltmarsh,
converted to a conservation easement, or cultivated with alternative salt-tolerant crops.
For these reasons, there will not be any further discussion of forestry management
beyond this stage.
6.3 Productivity/Economic Limitations
Coastal forests will be experience high levels of water stress and mortality at this
stage of salinization. At the point of chronic salinization, alternative crops and
conservation easements are the sustainable choice to gain additional profit off the
land. Few crops can perform at 100 percent yield in these sustained levels of salinity
(table 10). The market for alternative crops is less well established than traditional
crops and varies by region. Consumer demand may also be low for some of the
products from alternative crops. The approximate percent yield for some common
crops are shown below (table 10).
Table 9—Threshold tolerance of species that will grow
in Stage Three salinized soils
Common name Botanical name EC threshold (dS m
-1
)
Row Crops
Rye Secale cereale 11.4
Wheat (semidwarf) Triticum aestivum 8.6
Barley Hordeum vulgare 8.0
Sugar beet/Red beet Beta vulgaris 7.0
Cotton Gossypium hirsutum 7.7
Triticale X Triticosecale 6.1
Wheat, durum Triticum turgidum 5.8
33
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Three
6.4 Environmental Impacts
Saltwater intrusion will expand the range of invasive halophytes. Common reed is
likely to be the dominant species in salt-impacted coastal ecosystems. Invasive species
can rapidly colonize abandoned agricultural fields due to their high nutrient levels and
low organic matter.
Saltwater intrusion will impact the biogeochemistry of the environment. Saltwater
contains sulfides, which react with iron oxides in the soil. Once the soil’s sulfide
buffering capacity has been reached, available iron causes an accumulation of free
sulfides in soils and sediments. Sulfur inputs from saltwater impact biogeochemical
reactions, including phosphorus cycling and phosphorous export to surrounding
waters. Sulfidation creates a toxic environment for plants and causes plant stress and
death.
13
6.5 Adaptation Measures
Halophyte agriculture may allow impacted lands to remain viable and productive.
Management practices (e.g., crop-pasture rotation, salt-tolerant buffers) and
conservation practices may help prolong cultivation practices. Alternative crops, such
as salt meadow cordgrass (Spartina patens), seashore mallow (Kosteletzkya virginica),
switchgrass (Panicum virgatum), coastal panicgrass (Panicum amarulum), prairie
cordgrass (Spartina pectinata), and Eastern gamagrass (Tripsacum dactyloides) can
be planted in an entire field, not just in buffers or field edges as recommended in
previous salinization stages. If continued cultivation of the land is not pursued, field
abandonment will allow the inward migration of wetlands and marshes.
Specialty markets for halophytic crop products harvested from the natural tidal
marsh or limited commercial production are being investigated on a small scale in the
Table 10—Percent crop yield at the low and high limits of Stage Three soil
salinization for row crops and vegetables at 8 dS m
-1
to 16 dS m
-1
Crop Botanical name % Yield at 8 dS m
-1
% Yield at 16 dS m
-1
Row Crops
Rye Secale cereale 100 50
Wheat (semidwarf) Triticum aestivum 100 78
Barley Hordeum vulgare 100 83
Sugar beet/Red beet Beta vulgaris 94 47
Cotton Gossypium hirsutum 98 57
Triticale X Triticosecale 95 75
Quinoa Chenopodium quinoa willd 91 75
Wheat, durum Triticum turgidum 92 61
Wheat Triticum aestivum 95 74
Sorghum Sorghum bicolor 81 0
Sugarcane Saccharum oicinarum 63 16
Vegetables
Asparagus Asparagus oicinalis 92 76
Celery Apium graveolens 62 12
Species with zero yield at the high end of Stage Three salinity include: alfalfa, artichoke, broadbean, broccoli, cabbage,
carrot, cherry tomato, corn, cucumber, eggplant, flax, garlic, grape, grapefruit, guar, guava, lemon, lettuce, muskmelon, onion
(seed), orange, pea, pepper, potato, radish, rice, sorghum, soybean, spinach, squash, squash (scallop), sweet potato, tomato,
turnip, and zucchini.
34
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Three
Mid-Atlantic States and on a larger scale in Europe. Restaurateurs in the Netherlands
are creating a demand for Glasswort (Salicornia) to be used in salads, soups, and as a
garnish for various foods. Demand is very high in Europe for glasswort, but there is
currently limited commercial production of this species. The demand may be slow to
evolve in the United States as markets are slow to develop. Halophyte agriculture may
eventually need to be adopted in localized geographic areas of the Eastern United States
to remain viable and productive.
Regardless of the crops planted, insurance and disaster recovery programs are available.
For example, the USDA Farm Service Agency Noninsured Crop Disaster Assistance
Program (NAP) provides financial assistance to producers of crops that cannot be insured
when low yields, loss of inventory, or prevented planting occur due to natural disasters.
Consult with the local extension agent, NRCS, and FSA field offices to learn more.
6.6 Probable Outcomes
As salinity levels continue increasing, fewer crops will be cultivated as a sustainable
income source. The profit from cultivation will decline as crop yield declines, up to
the point where continuing farming the land no longer makes economic sense. The
groundwater table will increase as sea level increases, making flooding more likely
and decreasing drainage rates following flooding. At this time, the soil may become
too wet to farm.
Forage field with salinity. (Photo coutesy of USDA Photo Library)
35
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Four
CHAPTER 7
Stage Four:
Noncommercial Upland
Stage Four salinized soils are no longer commercially viable with traditional farming
approaches. Although some crops will still have limited production in these soils,
the economic benefit will be marginal. Additionally, these soils frequently flood, so
harvesting becomes an increasing challenge. Therefore, this chapter focuses on using
these soils as a pasture or as a conservation easement to protect more inland areas
from decline.
Stage Four Characteristics
Stage Four is characterized by having high levels of salinity. Halophytes dominate the
landscape, and areas with standing water will become more prevalent. Stage Four salinity
soil productivity is no longer profitable for the cultivation of commercial crops due to high
salinity levels. Water levels are high, and areas of standing water emerge. Wetland and salt-
tolerant plant species begin to colonize aected areas. The land would best be suited for
use as a pasture or conservation easement.
EC: detectable
16<25 dS m
-1
Crop options: Halophytes
Halophyte grass species
Practically treatable? No
7.1 General Discussion
As saltwater intrusion progresses, soil salinity levels will exceed 16 dS m
-1
. Productivity
will be reduced, and traditional crop operations will no longer be economically feasible.
Almost none of the standard row crops grown across the Atlantic Coast will tolerate
these conditions, leaving room for the establishment of halophytic, salt-tolerant species.
Land managers might want to convert their salt-affected agricultural land directly to
wetland, receiving a one-time property payment through a conservation easement.
However, in some areas, conversion to non-cultivated working land may be possible,
which might give land managers more profitable opportunities. These options include
the conversion of cropland to biomass production or livestock-pasture operations. The
decision to pursue these should be discussed with a local extension agent.
7.2 Species Tolerance (Upper Threshold Limit)
NRCS has identified salt-tolerant herbaceous plants and their upper pH limits
recommended for conservation practices in Stage Four of salinity (table 11). The plant’s
upper pH limit must fall within the site’s soil pH class range to be effective (table 12).
36
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Four
Table 11—Relative alkaline pH/salt-tolerant herbaceous conservation plants
Upper pH limit Soil salt tolerances
Plant species/varieties/selections
Cordgrass, Saltmeadow (Spartina patens) ‘Flageo’ (NC), ‘Sharp’ (FL) 8.0 Strong
Cordgrass, Smooth (Spartina alterniflora) 8.0 Strong
Dropseed, Seashore (Sporobolus virginicus) 8.0 Strong
Paspalum, Seashore (Paspalum vaginiflorum) 8.0 Strong
Bermudagrass (Cynodon dactylon) ‘Coastal’, ‘Tifway’ 7.5 Strong
Coastal Panicgrass (Panicum amarum var. amarulum) ‘Atlantic’ (VA) 7.6 Moderate-Strong
Switchgrass (Panicum virgatum) High Tide Germ. (MD), Timber Germ. (NC), ‘Miami’ (FL) 7.5 Moderate-Strong
Bluestem, Little (Schizachrium socparium) Dune Crest Germ. (NJ) 8.5 Moderate
Cordgrass, Prairie (Spartina pectinata) Southampton Germ. (NY) 8.5 Moderate
Dropseed, Sand (Sporobolus cryptandrus) 8.0 Moderate
Te (Eragrostis tef) 8.0 Moderate
Lovegrass, Purple (Eragrostis spectablilis) 7.5 Moderate
Zoysiagrass (Zoysia japonica) ‘Meyer’, ‘SR9100’ 7.5 Moderate
Bluestem, Big (Andropogon gerardii) Suther Germplasm (NC) 8.0 Slight
Little Bluestem (Schizachyrium scoparium) Suther Germplasm 8.0 Slight
Bluestem, Splitbeard (Andropogon scoparius) Ft. Cooper Germ. (FL) 7.5 Slight
Gamagrass Eastern (Tripsacum dacyloides) ‘Highlander’ (MS), ‘Meadowcrest’ (NY) 7.5 Slight
Indiangrass (Sorghastrum nutans) ‘Americus’, Newberry Germplasm 7.5 Slight
Millet, Japanese (Echinochloa frumentacea) ‘Chiwapa’ (MS) 7.5 Slight
Paspalum, Florida (Paspalum floridanum) Mid-Atlantic Germ. (MD) 7.5 Slight
Cool Season Grasses
Alkaligrass (Puccinellia distans) ‘Fults’, ‘Salty’ 8.5 Strong
Sudangrass (Sorghum halpense) 7.5 Strong
Barley (Hordum vulgare) ‘Seco’ 8.5 Moderate-Strong
Fescue, Tall (Lolium arundinacea) ‘KY-31’, ‘Arid’, ‘Alta’, ‘Goar’,‘Mohave’ 8.5 Moderate
Fescue, Slender Creeping Red (Festuca rubra var. rubra) ‘Dawson’, ‘Shoreline’ 8.0 Moderate
Wildrye, Canada (Elymus canadensis) ‘Mandan’ 8.0 Moderate
Rye (Secale cereale) 8.0 Moderate
Ryegrass, Annual (Lolium multiflorum) 8.0 Moderate
Bentgrass, Creeping (Agrostis palustris) ‘Seaside’, ‘Southshore’ 7.5 Moderate
Ryegrass, Perennial (Lolium perenne) ‘Brightstar SLT’, ‘Manhattan 3’, ‘Catalina’, ‘Fiesta
III’, ‘Paragon’, ‘Divine’, ‘Williamsburg’
7.5 Moderate
Sweetgrass (Hierochloe odorata) 7.5 Moderate
Oats (Avena sativa) 8.5 Slight
Wheat (Triticum aestivum) 8.0 Slight
Fescue, Hard (Festuca trachyphylla) ‘Durar’, ‘Warwick’ 8.5 None
Fescue, Sheep (Festuca ovina) ‘Covar’ 8.0 None
Wildrye, Virginia (Elymus virginicus) Kinchafoonee Germplasm (FL) 7.5 None
Legumes/Forbs
Seaside goldenrod (Solidago sempervirens) Monarch Germplasm 7.5 Strong
Alfalfa (Medicago sativa) 8.5 Moderate
Yellow sweetclover (Melilotus oicinalis) 8.0 Moderate
Rape (Brassica napus) 7.5 Moderate
Clovers; (Trifolium spp.) White Dutch, Red, Ladino, Alsike 7.5 Slight
Table 12—Soil pH classes
pH Class pH
Ultra acid <3.5
Extremely acid 3.5-4.4
Very strongly acid 4.5-5.0
Strongly acid 5.1-5.5
Moderately acid 5.6-6.0
Slightly acid 6.1-6.5
Neutral 6.6-7.3
Slightly alkaline 7.4-7.8
Moderately alkaline 7.9-8.4
Strongly alkaline 8.5-9.0
Very strongly alkaline >9.0
37
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Four
7.3 Impacts
High salinity levels will initiate a transitional period in which colonization and the
eventual dominance by halophytic plant species will occur. The location of transition is
difficult to predict because the factors that cause the transition are complex. However,
the speed at which the transition process happens mainly depends on landscape slope
and disturbance pressures such as the area’s rate of sea-level rise and frequency of
storm surge/coastal flooding events.
Saltwater intrusion into the water table moves salinity levels farther inland while
storm surge events push standing water and marsh farther past the seaward boundary.
Shallow slope gradients increase the rate at which these boundaries move inland. As
water tables rise closer towards the soil surface, drainage capacity and productivity
will decrease, resulting in frequently saturated conditions. Due to the reduction in
drainage capacity, areas of standing water occur after heavy precipitation. These areas
may further enable halophyte and marshland pioneer species growth, resulting in more
significant management needs or abandonment of areas.
Most crops are reduced to zero yields in Stage Four. Table 13 shows an approximate
percent yield for the plants that tolerate EC values from 16 dS m
-1
to 25 dS m
-1
. As
these yield estimates are based on otherwise ideal growing conditions, even these are
unlikely to prove profitable in real growing conditions of Stage Four salinized lands.
Forestry
Forests can survive at Stage Four, though their productivity will be very low. Tree
mortality will lead to salt-tolerant vegetation such as cattail (Typha sp.), common reed,
and sawgrass (Cladium sp.) moving into the open spaces left by the dead trees. Salt-
tolerant species may pull additional salt to the soil surface due to their shallow roots.
Freshwater tree seedlings are unlikely to grow in a more saline environment.
28
7.4 Adaptation Measures
Potential marketability for biomass products is improving, especially within areas of
the Northeast. Livestock bedding materials created from cultivated salt-tolerant grass
species prove to be more effective than standard materials while also showing reduced
disease transmission in livestock. Implementation of these grass species creates
opportunities for biomass production and profit, and it may also work to stabilize soils
eroded by traditional crop rotations.
Table 13—Percent crop yield at the low and high limits of Stage Four soil
salinization for row crops and vegetables at 16 dS m
-1
to 25 dS m
-1
Crop Botanical name % Yield at 16 dS m
-1
% Yield at 25 dS m
-1
Row Crops
Wheat (semidwarf) Triticum aestivum 78 51
Cotton Gossypium hirsutum 57 10
Triticale X Triticosecale 75 53
Wheat, durum Triticum turgidum 61 27
Wheat Triticum aestivum 74 51
Vegetables
Asparagus Asparagus oicinalis 76 58
Species with zero yield at the high end of Stage Four salinity include: barley, celery, rye, sugar beet/red beet, and
sugarcane.
38
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Four
Conversion of cropland to livestock-pasture operations appears to have a much more
sizeable risk potential (e.g., hoof diseases and injury risk from the uneven ground) than
biomass production. Livestock systems require land managers to possess an alternative
skill set compared to traditional crop rotation systems.
30
While livestock readily digests
halophytic plant tissues, these species possess high mineral content and low energy
content levels that have been linked to weight loss and other detrimental effects.
However, studies have shown the feasibility of mixed halophyte forage implementation
in livestock diets. With proper freshwater access, forages containing a blend of high
energy components (i.e., legumes) and halophytic plant species may be used in
livestock production. The economic feasibility of conversion to livestock-pasture
operations would rely on conversion costs (i.e., equipment, inventory, planting costs)
and the ability to produce high-energy forage components on non-impacted land.
Other options to consider include leasing the land for hunting, selling, or donating land
into a conservation easement. Conservation easements reduce the property tax on the
land, which is economically beneficial, protects the land during transition to saltmarsh,
and allows the landowner to retain property rights and amenities while agreeing
not to use the land for development purposes. They can also provide recreational
opportunities in hunting, fishing, and wildlife-related recreation, which also brings
economic benefits to the surrounding community. Additional Conservation Programs
by the NRCS are discussed further in Appendix V.
Regardless of the crops planted, every landowner should take advantage of available
insurance and disaster recovery programs. For example, the USDA Farm Service Agency
Noninsured Crop Disaster Assistance Program (NAP) provides financial assistance
to producers of crops that cannot be insured when low yields, loss of inventory, or
prevented planting occur due to natural disasters. Consult with the local extension
agent, NRCS, and FSA field offices to learn more.
7.5 Probable Outcomes
Eventually, soil-water content and regular standing water will become too high and
frequent to maintain pastureland and livestock. Many of the potential forage plant
species will not tolerate both high salinity levels and inundation. Land managers
should consider enrolling in wetland easements or promoting the restoration of native
wetland vegetation. The local NRCS field staff or extension agent can provide details
on options and how to enroll. Despite the loss of profitable land, conversion to wetland
entails other benefits such as monetary compensation, tax incentives, and added flood
and erosion protection for adjacent farmlands. To maximize the benefits of conversion,
proper planning and communication between the land manager and specialists, such
as local extension agents, is crucial.
39
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
CHAPTER 8
Economic Case Study
An economic case study was carried out to determine certain crops’ economic
profitability in the first four salinization stages. The case study was based solely on
crop prices without the consideration of government incentives and subsidies. The
study area was the Tidewater Area in eastern North Carolina, an area of roughly 2.8
million acres (11,600 km
2
) that includes the cities of Creswell, Edenton, Elizabeth City,
Kitty Hawk, Morehead City, Pantego, and Swan Quarter as well as Capes Hatteras and
Lookout and Ocracoke Island.
Converting tidewater wetlands for agricultural purposes has occurred by section over
a long time. By the late 18th century, the first large-scale drainage of deep organic soils
had begun in Washington County for rice production. A century later, large areas in the
northeastern part of the State around the Great Dismal Swamp and on the Albemarle-
Pamlico Peninsula had been converted to cropland. Around this time and into the
early 20th century, timber companies acquired large tracts of coastal swampland for
logging, especially for shingles from Atlantic white cedar. With the desirable timber
removed, much of this land was sold for development. In the years after World War II,
as equipment and cultural practices improved and competition for land increased, land
conversion to cropland gained momentum in the Tidewater Area.
The area is a nearly level coastal plain crossed by broad, shallow valleys containing
meandering river channels. Elevation ranges from sea level to <25 feet (7.6 m).
Generally, local relief is <3 feet (1 m). Most valleys terminate in the estuaries along the
coast, where tidal marshes are being created by sea-level rise.
The Tidewater Area has extensive pocosins, formations of decomposed peat. Pocosins
form from accumulating dead plant material and its transformation into a muck, and
are found on broad, flat inter-stream divides with few dissecting streams for water
removal. The soil materials underlying them are slowly permeable clayey to sandy
mineral sediments that remain water-logged almost perpetually.
Together, these factors led to the formation of cypress and Atlantic white-cedar
forests. Under the anaerobic and acidic conditions, organic matter decayed slowly
and accumulated while the forests eventually drowned in the accumulating muck or
burned and fell.
Since 1890, sea level has risen about 1 foot (0.3 m), with implications for the long-
term, continued intensive use of this area. Much of the land on the Albemarle-Pamlico
Peninsula is <5 feet (1.52 m) above sea level. Coastal shoreline erosion is symptomatic
of long-term, continuing sea-level rise.
Methods
Crop budgets were developed using North Carolina State University (NCSU)
Agricultural and Resource Economics (ARE) Enterprise Budgets for the Tidewater
Area for each crop and production system combination. All crop budgets were for the
crop year 2019. All variable and fixed costs, input rates, and amounts used were those
40
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
contained in the budgets. All costs were adjusted to 2019 prices using the Bureau of
Labor Statistics CPI Inflation Calculator. Labor and tractor/machinery cost estimates
were for those directly associated with field operations (i.e., planting and harvesting).
Production systems considered in this analysis included conventional tillage (CV), no-
tillage (NT), strip-tillage (ST), and organic (O). Corn and soybean were analyzed using
all four production systems. Cotton was analyzed using conventional and no-tillage,
while wheat was analyzed using conventional tillage and organic production.
The switchgrass budget assumed that there was already an established stand.
Establishment costs were allocated to fixed costs and depreciated over 20 years.
Switchgrass yield declines were 74 percent at EC=5 and 44 percent at EC=10. Crop
yields in the enterprise budgets were considered from non-saline settings, i.e., EC=0,
and adjusted by the percentage decline associated with the electrical conductivity levels
of 2, 4, 8, and 16 (see tables 6, 7, and 10 above).
Corn, soybean, and wheat prices and basis were averages taken from the usual month
of harvest at elevators and feed mills in Cofield, Creswell, Elizabeth City, and LaGrange,
NC, and Norfolk and Wakefield, VA. Cotton prices were those provided by the cotton
enterprise budgets. Switchgrass biomass prices were taken from the Internet Hay
Exchange.
Results
Net returns and yields per acre for each crop and production system combination at the
soil electrical conductivity (EC) levels of 0, 2, 4, 8, and 16 (0, 5, and 10 for switchgrass)
are given in the tables below. Net returns are returns to land, labor, capital, and
management calculated as gross revenue minus all variable and fixed costs following
harvest. Gross revenue was estimated by multiplying crop yield times the crop price at
harvest.
Corn
Most Tidewater corn is planted in April and the early part of May. Usually, the crop is
harvested in September or early October, but harvesting may extend to as late as mid-
November. Much of the crop is used in livestock feed. However, the use of corn for
biofuel production fuel has risen substantially over the last 15 years.
Corn is sensitive to salinity, and yields begin to decline early in the onset of Stage One
salinity levels. Corn is generally not commercially viable by Stage Two levels regardless
of the production system employed. However, organic production may remain
profitable into Stage Two’s lower salinity levels due to the product’s premium per-
bushel price. Price drops of as little as 5–10 percent can significantly erode profitability.
Net returns varied by cropping systems. The non-organic systems’ per-acre net
returns were positive ($40 to $76 per acre) in Stage One salinity levels, although 6- to
13-percent lower than at Stage Zero. With the onset of Stage Two salinity levels, net
returns became negative (-$4 to -$41 per acre) and continued to decline as salinity
increased. Organic production net returns were positive ($274 per acre) in Stage One
and remained so through Stage Two levels ($123 per acre). However, organic corn
was the only corn production system with a positive return at the beginning of Stage
Two, which highlights the dependence of the crop’s success on premium (organic)
per-unit prices.
41
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Table 14—Crop yield under varying production systems and electrical conductivity (EC)
Soil electrical conductivity (EC) (dS m
-1
)
0 2 4 8 16
| Stage 0 | Stage 1 | Stage 2 | Stage 3 |
Crop
Production
System Crop Yield (tons per acre)
Corn CV
1
149 148 125 80 0
Corn NT
2
149 148 125 80 0
Corn ST
3
148 147 124 80 0
Corn O
4
107 106 90 58 0
Cotton CV
830 830 830 813 473
Cotton NT
900 900 900 882 513
Soybean CV
41 41 41 16 0
Soybean NT
41 41 41 16 0
Soybean ST
41 41 41 16 0
Soybean O
30 30 30 12 0
Wheat CV
50 50 50 50 39
Wheat O 43 43 43 43 34
Soil electrical conductivity (EC) (dS m
-1
)
1.2# 5# 10#
Switchgrass bio-mass 6 4 3
1
Conventional tillage
2
No tillage
3
Strip tillage
4
Organic
#Sun, Y.; Niu,G.; Ganjegunte, G.; Wu, Y. 2018. Salt tolerance of six switchgrass cultivars. Agriculture. 8(5): 66. https://doi.org/10.3390/agriculture8050066.
Table 15—Net returns for crops under varying production systems and electrical conductivity (EC)
Soil electrical conductivity (EC) (dS m
-1
)
0 2 4 8 16
| Stage 0 | Stage 1 | Stage 2 | Stage 3 |
Crop
Production
System Net Return (dollars per acre)
Corn CV
1
69 64 (17) (179) (470)
Corn NT
2
46 40 (41) (202) (494)
Corn ST
3
81 76 (4) (165) (454)
Corn O
4
283 274 123 (180) (726)
Cotton CV 47 47 47 34 (232)
Cotton NT 106 106 106 92 (196)
Soybean CV 4 4 4 (198) (332)
Soybean NT (12) (12) (12) (214) (348)
Soybean ST 34 34 34 (167) (301)
Soybean O 124 124 124 (225) (457)
Wheat CV (30) (30) (30) (30) (76)
Wheat O (62) (62) (62) (62) (160)
Soil electrical conductivity (EC) (dS m
-1
)
1.2# 5# 10#
Net Return (dollars per acre)
Switchgrass bio-mass 30 (74) (194)
1
Conventional tillage
2
No tillage
3
Strip tillage
4
Organic
#Sun, Y.; Niu,G.; Ganjegunte, G.; Wu, Y. 2018. Salt tolerance of six switchgrass cultivars. Agriculture. 8(5): 66. https://doi.org/10.3390/agriculture8050066.
42
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Cotton
In Tidewater cotton fields, planting season begins early in May and usually concludes
by mid-June. Cotton harvest peaks in October and November but may run into mid-
December. Most Tidewater cotton is upland or short-staple cotton used in clothing, and
for home and hospital/medical uses.
Cotton can tolerate higher soil salinity levels, maintaining high productivity levels
through Stage Two and into the lower salinity levels of Stage Three. However, once
salinity levels exceed an EC of ~8 dS m
-1
, productivity falls off rapidly. In the lower
range of salinity in Stage Three, the net returns were positive for both conventionally
tilled ($34) and no-tillage ($92) cotton production systems. However, as salinity
increased, net returns fell significantly.
Soybeans
Soybeans are generally planted in late May and June in the Tidewater Area. Harvesting
is usually completed in November but may begin in October and extend to mid-
December. Tidewater producers tend to have lower yields and higher per-bushel
production costs relative to producers in other soybean producing areas of the United
States. Higher yields reduce per-bushel production costs.
Soybean yields are unaffected by Stage One salinity levels. However, as salinity levels
move into Stage Two, the crop’s yields rapidly decline. Net returns using CV, ST, and
organic production systems were positive through Stage One and the lower levels of
Stage Two, while those using NT were negative in all salinity stages. Returns were
marginal ($4 per acre) using conventional tillage systems. Strip tillage returns ($34 per
acre) were higher, but the organic production system offered even higher returns. The
per-acre net returns for organic production were the second highest of all the crop-
production systems analyzed. Remembering that the high net returns from organic
soybean production are dependent on premium per-bushel prices that may or may not
be sustainable is important. In Stage Three salinity levels, soybean net returns for all
production systems were negative (-$167 to -$225 per acre).
Wheat
Soft red winter (SRW) wheat is grown in the Tidewater Area of North Carolina. The
wheat is sown in the fall, giving the crop time to establish before becoming relatively
dormant with the arrival of cold winter temperatures. The crop resumes growth in the
spring and is usually harvested in early summer. By late July in North Carolina, most
wheat has been harvested.
Wheat is one of the few crops relatively unaffected by higher Stage Three soil salinity
levels. Even at the onset of Stage Four, wheat yields remain high relative to almost all
other species. However, the yields are probably not commercially viable.
Despite wheat’s resilience to increasing soil salinity, net returns remained negative
across the entire EC spectrum. Even the premium per-bushel prices associated with
organic production could not push returns into the positive. Relative to other wheat-
producing regions, Tidewater Area growers may face marginal yields and high
production costs, which reduces profitability. Warmer, humid growing conditions there
may reduce yields and increase pest pressures, which increase production costs. Higher
yields reduce per-bushel production costs.
43
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Switchgrass
Percentage yield declines available for switchgrass were not as detailed as those of
the other crops. Yield decline estimates for electrical conductivities of 1.2, 5, and 10
were available, and those corresponded with Stages Zero, Two, and Three soil salinity
ranges. In Stage Zero, returns for switchgrass biomass were positive ($30 per acre) but
became negative (-$74 per acre) in Stages Two and Three.
Conclusions
Except for wheat and no-tillage soybeans, net returns per acre were positive at the
beginning of Stage One. Cotton had the highest salinity tolerance and was able to
produce a positive net return at the beginning of Stage Three. Once a species’ threshold
soil salinity tolerance was reached, net returns quickly became negative.
Despite being the most salt-tolerant crop, wheat net returns were never positive across
all soil salinity levels, including non-saline. Even premium prices could not push
organic wheat production into positive territory. The negative wheat returns reflect
overall market conditions for the commodity. For several years, wheat plantings
and production have been on a long-term downward trend. According to the USDA
Economic Research Service, since peaking in 1981, U.S. wheat planted has dropped by
more than 30 million acres, with production falling by close to 900 million bushels.
35
Across all soil salinity levels, organic corn and soybean production yields were 25- to
30-percent lower than those for all tillage-based production systems. Despite the yield
reductions, organic corn and soybean production offered attractive net returns for 2019.
However, those returns are most likely anchored in the premium per-bushel prices paid.
Small declines in product prices can quickly erode positive net returns.
There seems to be a soil salinity level threshold for all crops but cotton. Net returns
from cotton production remained positive for all but the highest soil salinity levels.
Once salinity levels enter the Stage Two range, net returns decline quickly into the
negative, and aside from cotton, few cropping options remain.
44
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Five
CHAPTER 9
Stage Five:
Saltmarsh
The soil in a Stage Five field has transitioned into a semi-aquatic system, with standing
or tidal brackish water often present. Grazing is no longer a likely option, as water, foot
rot, and potential for unseen holes pose a danger to livestock. Although not viable for
commercial production, saltmarshes are important waterfowl and wildlife habitats,
and these areas could have the potential for inland protection, hunting leases, and
recreational or aesthetic value. Additionally, the land has value as a conservation
easement. The environmental characteristic of different wetland ecosystems is shown
in table 16.
Stage Five Characteristics
Stage Five is characterized by having high salinity and being influenced by the tides.
Saltmarsh species and open water become present in the landscape. Stage Five salinity
soils have converted to a saltmarsh, with high salinity levels and some open water. The area
is regularly flooded by tides.
EC: detectable
>25 dS m
-1
Crop options: none
Practically treatable? No
9.1 General Discussion
As further saltwater intrusion occurs, the cost-effectiveness of cultivation and running
operations will decrease. However, managing these areas may still provide benefits
in the form of ecosystem services. Saltmarsh environments sequester more carbon
annually compared to agricultural lands
36
and can help stabilize eroding shorelines.
Many native species occupy saltmarsh environments leading to greater biodiversity
rates. Natural lands tend to increase public attention and the desire for recreational
areas as well. Marshes and wetlands also improve water quality through their ability
Table 16—The environmental characteristics of dierent wetland ecosystems
Site characteristics Saltmarsh Brackish wetland
Water classification Saltwater Mix of fresh and salt
Salinity High (20–35 ppt) Varies (0.5–20 ppt)
Vegetation Herbaceous Woody and herbaceous
Ocean influence Tidal Tidal and event-based
Location Coastal Transition zone
45
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Five
to filter contaminants and sediments. Saltmarsh ecosystems can reduce impacts
from coastal flooding and damages associated with hurricane activity. Reductions in
coastal mangrove/marshland areas raise the potential for severe damages to vulnerable
infrastructure, cities, and inland ecosystems.
37
Working lands may be converted to a
wetland easement where the landowner receives payment for converted acreage. The
benefits of conversion would protect adjacent farmland and provide benefits to the
surrounding ecosystems and communities.
9.2 Impacts
As sea levels continue to rise, saltmarsh ecosystems move farther inland in a
phenomenon called “marsh migration.” As these areas migrate, the threat of invasive
plant species increases. For example, the common reed is known to outcompete and
replace critical native species. Saltwater intrusion and marsh migration inland also
pose a severe threat to forest land along the coast. Hardwood species (e.g., oak, maple,
and hickory) that are sensitive to soil salinity and inundation start to die and rot from
the bottom up. Eventually, as salinity increases, more salt-tolerant species such as
loblolly pine, holly, beech, and sweetgum will also die.
38
These decaying forest areas are
referred to as “ghost forests” due to the large-scale mortality and discoloration of the
rotting bark. Ghost forest formation is typically followed by conversion to saltmarsh.
Areas such as ghost forests provide a space for marshes to migrate inland, which is
necessary for tidal marsh ecosystem persistence as sea levels rise.
9.3 Species Tolerance
Saltmarshes are inhabited by plant species able to tolerate moderate to high salinity
ranges. Soil salinity and inundation state are variable within different marsh zones.
The low marsh zone area is usually at a low elevation and in direct contact with open
water or the saltwater source; therefore, the low marsh experiences frequent flooding
associated with the tidal activity. Species that are salt-tolerant and can withstand long
periods of inundation thrive in the low marsh zone.
The zone residing above the low marsh is referred to as the high marsh zone. The
high marsh may encompass large swaths of the area and tends to be saturated with
infrequent inundation. High marshes can be saltier than low marshes because of
evaporation, and less frequent tidal flushing increases soil salt concentrations. This
zone contains few grass and flowering species.
At higher elevations, high marsh begins to blend into an area referred to as the upland
border. This zone has high biodiversity due to low saturation levels and reduced soil
salinity. Depressions within the high marsh area’s microtopography are referred to
as pannes and frequently fill with stagnant water. Salinity levels within and around
pannes tend to be significantly higher than the surrounding high marsh. Deep pannes
that remain filled for extended periods are denoted as pools. Species that occupy the
various saltmarsh zones can be found in table 17 on the following page.
46
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Five
9.4 Adaptation Measures
During the conversion of cropland to saltmarsh,
proper management must promote the valuable native
species that will yield the most benefits to the area
and landowner. Leaving the area unmanaged results
in a deficient wetland environment and the promotion
of salt-tolerant and invasive plant species. Many of
the plant species used as traditional forages will not
tolerate salinity levels above the Stage Four threshold.
When going through the conversion process, land
managers, in cooperation with a local extension agent,
should select a sensible variety of salt-tolerant species
or nurse plants that may help with the transitioning
of the working land. These species help to create an
environment where key species are unhindered by soil
quality or invasive species.
Regardless of the crops planted, every landowner
should take advantage of available insurance and
disaster recovery programs. For example, the USDA
Farm Service Agency Noninsured Crop Disaster
Assistance Program (NAP) provides financial
assistance to producers of crops that cannot be
insured when low yields, loss of inventory, or
prevented planting occur due to natural disasters.
Consult the local extension agent, NRCS, and FSA
field office for more information.
9.5 Probable Outcomes
As sea levels continue to rise at an accelerated rate,
saltmarsh ecosystems will eventually transition into
open water areas. The amount of time saltmarshes
can persist is uncertain and depends on the natural
and anthropogenic drivers of saltwater intrusion.
39
If accretion levels are high, marshes may persist for
long periods due to their ability to maintain elevations
relative to sea level. The impacts of climate change
near coastal areas are not entirely known, though
inland drought frequency may play a significant role
in saltmarsh ecosystems changes.
9.6 Stage Six: Open Water
As water inundation continues, the site transitions
to a fully aquatic ecosystem. The characteristics of
different types of marine ecosystems in shown in table
18. In the southeast Atlantic Coast, roughly 44 km
2
(10,873 acres) of dry land and wetlands were converted
to open water from 1996 to 2011.
40
From 1985 to 2010,
Louisiana’s coast lost an average of 42.99 km
2
(10,623
Table 17—Common species present in
Stage Five salinity soils
Low marsh
Smooth cordgrass (Spartina alterniflora)
Seashore alkali grass (
Puccinellia maritima
)
Seaside arrow grass (Triglochin maritimum)
Narrowleaf cattail (Typha angustifolia)
Sea cavender (Limonium nashii)
Glasswort (Salicornia spp.)
High marsh
Saltmarsh aster (Symphyotrichum subulatum)
Spike grass (Distichlis spicata)
Black grass (Juncus gerardii)
Needlegrass (Juncus roemerianus)
Saltmeadow grass (Spartina patens)
Seashore gaspalum (Paspalum vaginatum)
Coastal dropseed (Sporobolus virginicus)
Rose mallow (Hibiscus moscheutos)
Seashore mallow (Kosteletzkya virginica)
Upland border
Switchgrass (Panicum virgatum)
Coastal panicgrass (Panicum amarulum)
Sweet gale (Myrica gale)
Wax myrtle (Myrica cerifera)
Groundsel (Baccharis halimifolia)
Marsh elder (Iva frutescens)
Seaside goldenrod (Solidago sempervirens)
Pannes
Glasswort (Salicornia ssp.)
Smooth cordgrass (Spartina alterniflora)
Pools
Widgeon grass (Ruppia Maritima)
Eelgrass (Zostera marina)
47
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Stage Five
acres) of land per year to open water.
41
Depending on the topography, tides, fresh- and
saltwater water input ratios, and other factors, the area could range from slightly
brackish to seawater. Management of this newly created marine ecosystem is beyond
the scope of this guide.
Table 18—Characteristics of dierent types of marine ecosystems
Classification EC in dS m
-1
EC in uS cm
-1
mM NaCl ppt ppm mg Cl L
-1
Freshwater 0.8 800 8 0.5 500 280
Slightly brackish 1.7 1700 17 1 1000 600
Medium brackish 1.7 - 8 1700 - 8000 17 - 80 1 - 5 1000 - 5000 600 - 2800
Brackish 8 - 25 8000 - 25000 80 - 250 5 - 15 5000 - 15000 2800 - 9000
Strong brackish 25 - 58 25000 - 58000 250 - 580 15 - 35 15000 - 35000 9000 - 18000
Seawater 58 58000 580 35 35000 18000
Brine > 58 > 58000 > 580 <35 >35000 >18000
Saltmarsh. (Photo courtesy of Needpix)
48
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
APPENDIX I
Useful Tools and Resources
Resources
NC State tool useful for cost-revenue analysis of implementing SRWC within North Carolina
https://projects.ncsu.edu/project/bioenergy/SR_Hardwoods.html
Factsheet guidance from Mississippi State Extension on SRWC
http://extension.msstate.edu/sites/default/files/publications/publications/p3019.pdf
BioSAT
Host of tools and factsheets on SRWC cost assessment and suitability
Suitability Index: http://www.biosat.net/index.html
Factsheets: http://www.biosat.net/FactSheets.html
Harvesting and Transportation cost tools: http://www.biosat.net/Toolset.html
NOAA Sea Level Rise Map Viewer
Useful large-scale map viewer showing sea-level rise, marsh migration, high-tide flooding
potential, and population vulnerability for the United States
https://coast.noaa.gov/slr/#/layer/slr/0/-11581024.663779823/5095888.569004184/4/
satellite/none/0.8/2050/interHigh/midAccretion
Union of Concerned Scientists SLR Fact Sheet
A factsheet detailing causes and measurement of sea-level rise along with vulnerable land
areas and populations
https://www.ucsusa.org/sites/default/files/legacy/assets/documents/global_warming/
Causes-of-Sea-Level-Rise.pdf
Smithsonian SLR
Smithsonian sea-level rise resource on impacts and measurement
https://ocean.si.edu/through-time/ancient-seas/sea-level-rise
U.S. Climate Resilience Toolkit
Shows sea-level rise estimates from 2020–2100 corresponding with emission/climate change
scenarios. Provides NOAA’s interactive relative sea-level trends map
https://toolkit.climate.gov/
Coastal Salinity Index
Developed by USGS in cooperation with NOAA and National Integrated Drought
Monitoring System (NIDIS)
https://www2.usgs.gov/water/southatlantic/projects/coastalsalinity/home.php
Noninsured Crop Disaster Assistance Program (NAP): provides financial assistance to
producers of uninsurable crops when low yields, loss of inventory, or prevented planting
occur due to natural disasters
https://www.fsa.usda.gov/programs-and-services/disaster-assistance-program/
noninsured-crop-disaster-assistance/index
49
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Regional Variability in Alternative Crop Markets
Advice on alternative crop systems and markets—University of Maryland
https://extension.umd.edu/agmarketing/alternative-enterprises
Alternative Crop Resource—USDA
https://www.nal.usda.gov/afsic/list-alternative-crops-and-enterprises-small-farm-
diversification
Alternative/Specialty Crop Marketing—NCSU
https://newcropsorganics.ces.ncsu.edu/specialty-crops/specialty-crops-marketing/
Crop Selection and Market Implications—UGA
https://extension.uga.edu/publications/detail.html?number=B1398&title=Nursery%20
Crop%20Selection%20and%20Market%20Implications
Halophytes
http://www.biosalinity.org/halophytes.htm#Why_Halophytes_Economic
_&_Environmental_
Food and Agriculture Organization of the United Nations Factsheet/Portal
http://www.fao.org/agriculture/crops/thematic-sitemap/theme/spi/scpi-home/managing-
ecosystems/integrated-crop-livestock-systems/en/SARE Presentations
https://www.sare.org/Learning-Center/Conference-Materials/2014-National-
Conference-on-Cover-Crops-and-Soil-Health/Grazing-Cover-Crops-and-Benefits-for-
Livestock-Operations
USDA NRCS Pennsylvania
https://www.nrcs.usda.gov/wps/portal/nrcs/detail/pa/soils/health/?cid=nrcseprd1204610
50
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
APPENDIX II
Native Plant Species Salt Tolerances
by Condition
Plant species have varying tolerance levels to salt spray, soil saturated with saltwater,
and infrequent flooding of brackish water. In table A1, the more tolerant species are
denoted by “X” and “*” denotes low/medium tolerance species. Plant species can be
tolerant to direct salt spray or indirect/infrequent salt spray. The tolerance of plant
species to soil saturated with saltwater and flooding with brackish water is based on
the salinity (ppt) they can withstand.
Table A1—Native plant species salt tolerances by condition
Botanical name Plant Salt spray Saltwater Flooding
SHRUBS/VINES/GROUNDCOVER
Amorpha fruticosa Indigobush X *
Arctostaphyllos uva-ursi Bearberry * * *
Aronia arbutifolia Red chokeberry * *
Aronia melanocarpa Black chokeberry * *
Baccharis halimifolia Groundsel bush X X X
Cephalanthus occidentalis Buttonbush * *
Clethra alnifolia Sweet pepperbush * * *
Ilex glabra Inkberry * * X
Ilex decidua Possumhaw * *
Iva frutescens Marsh elder X X X
Juniperus conferta Seashore juniper X * X
Lindera benzoin Spicebush * *
Magnolia virginica Sweetbay * *
Morella pensylvanica Bayberry X * *
Myrica cerifera Wax myrtle X * X
Parthenocissus quinquefolia Virginia creeper * * *
Prunus maritima Beach plum X * X
Rosa carolina Pasture rose * * X
Rosa rugosa Rugosa rose X * X
Rosa virginiana Virginia rose * * *
Rhus copallina Winged/Dwarf sumac * * *
Salix discolor Pussy willow * *
Sambucus canadensis Elderberry * *
Vaccinium corymbosum Highbush blueberry * *
Viburnum dentatum Southern arrowwood * *
51
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Botanical name Plant Salt spray Saltwater Flooding
TREES
Alnus serrulata Smooth alder *
Amelanchier canadensis Serviceberry/Shadbush * * *
Celtis occidentalis Hackberry X *
Juniperus virginiana Eastern red cedar X * *
Ilex opaca American holly X * *
Populus deltoides Eastern cottonwood * * *
GRASSES/GRASSLIKES
Ammophila breviligulata American beachgrass X X X
Distichlis spicata Saltgrass X X X
Juncus gerardii/roemarianus Blackgrass/Needlerush X X X
Panicum virgatum Switchgrass * * X
Panicum amarum Bitter panicgrass X X X
Panicum amarulum Coastal panicgrass X * X
Schizachyrium littorale Seacoast bluestem X X X
Scirpus tabernaemontanii Hardstem bulrush * * *
Scirpus americanus Three square * * *
Scirpus robustus Saltmeadow bulrush * X X
Spartina alterniflora Smooth cordgrass X X X
Spartina cynosuroides Giant cordgrass * * *
Spartina pectinata Prairie cordgrass * * *
Spartina patens Saltmeadow cordgrass X X X
Tripsacum dactyloides Eastern gamagrass * * *
Typha angustifolia Narrow-leaf cattail * * *
FORBS
Hibiscus moscheutos Marsh hibiscus * * *
Kosteletzkya virginica Seashore mallow X * *
Lathyrus maritimus Beach pea X * *
Solidago sempervirens Seaside goldenrod X X X
1. Salt spray
X = tolerance to direct salt spray
* = tolerance to indirect/infrequent salt spray
2. Saltwater (soil saturated)
X = strong tolerance (up to 25–35 ppt sodium chloride concentration)
* = low/medium tolerance (up to 10–15 ppt sodium chloride concentration)
3. Flooding tolerance = tolerance to infrequent flooding of brackish water
X = strong tolerance (up to 25–35 ppt sodium chloride concentration)
* = low/medium tolerance (up to 10–15 ppt sodium chloride concentration)
52
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
APPENDIX III
Unit Conversions
The following conversions produce approximate total dissolved solids (TDS) and parts
per million (ppm) values and should not be taken as absolute and accurate values.
Handy Unit Conversions:
Milligrams per liter (mg/l or mg l
-1
) equals parts per million (ppm).
Example: 125 mg l
-1
= 125 ppm.
Percentage multiplied by 10,000 equals parts per million (ppm), or conversely, parts per
million (ppm) divided by 10,000 equals percentage (%).
Example: To convert 2% (0.02 x 100) to ppm, multiply 2 times 10,000 to get
20,000 ppm. Do not confuse the fraction 0.02 with 2 percent when converting.
However, if the percentage were actually 0.02% (0.02/100 or 0.0002), then the
conversion would correctly be 0.02 x 10,000 = 100 ppm.
Milligrams per liter (mg l
-1
) = parts per million (ppm).
Example: 20 mg l
-1
= 20 ppm.
Electrical Conductivity (EC) x 640 = Total dissolved solids (TDS) of lesser saline soils
Electrical Conductivity (EC) x 800 = Total dissolved solids (TDS) of highly saline soils
Example: the TDS of a very slightly saline soil with an EC of 2.5 dS cm
-1
can be
approximated by multiplying 2.5 X 640 = 1,600 ppm or 0.16 percent or 0.0016.
53
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
APPENDIX IV
Electrical Conductivity (EC) Testing
Laboratories by State
Alabama—Special Soil Analysis https://ssl.acesag.auburn.edu/anr/soillab/
Delaware—Soluble Salts Test https://www.udel.edu/canr/cooperative-extension/
environmental-stewardship/soil-testing/
Florida http://edis.ifas.ufl.edu/ss186
Georgia http://aesl.ces.uga.edu/
Louisiana—Optional Soil Test https://www.lsuagcenter.com/portals/our_offices/
departments/spess/servicelabs/soil_testing_lab
Maryland https://extension.umd.edu/hgic/topics/soil-testing
Mississippi—only measures TSS http://extension.msstate.edu/lawn-and-garden/
soil-testing
New Jersey https://njaes.rutgers.edu/soil-testing-lab/
North Carolina—only gives soluble
salt index (10-5 mho/cm) http://www.ncagr.gov/agronomi/uyrst.htm
South Carolina—same as NC https://www.clemson.edu/public/regulatory/
ag-srvc-lab/soil-testing/index.html
Virginia—same as NC https://www.soiltest.vt.edu/fees-and-forms.html
lef t: Soil pH test kit. (Photo courtesy of CSIRO Forestry and Forest Products, Wikimedia Commons; CC BY 3.0 license);
right: Well testing. (Photo courtesy of USDA Photo Library)
54
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
APPENDIX V
Conservation and Farm Bill Programs
The following programs can be used in most of the salinization stages. To find
programs available in your area, contact your local NRCS field staff. Conservation and
Farm Bill programs should be discussed with your local NRCS field staff. NRCS field
office staff are more knowledgeable on these programs and work with producers and
landowners to determine which one(s) are more feasible depending on farm-specific
resource concerns and farmer objectives.
Conservation Programs Administered by the Natural Resources
Conservation Service
On the public side, the U.S. Government has established financial incentive programs
intended to preserve wetlands and other ecosystems that promote compensation, not
avoidance or minimization. The Agricultural Conservation Easement Program (ACEP)
and the Conservation Reserve Program/Conservation Reserve Enhancement Program
(CRP/CREP) are the NRCS’s two main wetland programs.
Agricultural Conservation Easement Program (ACEP)
The Agricultural Conservation Easement Program replaced the Wetlands Reserve
Program (WRP) in 2014 under the new Farm Bill. The wetlands portion of ACEP is a
continuation of the WRP, now referred to as the WREP (Wetland Reserve Enhancement
Partnership). The WREP/ACEP is specifically intended to assist landowners in
protecting, restoring, and enhancing wetlands on their property. The WREP/ACEP is
a joint effort between the USDA-NRCS and State and local governments. The WREP/
ACEP encompasses three different enrollment options—permanent easements, 30-year
easements, and restoration cost-share agreements. Most easements fall into the first
category and are protected for perpetuity.
Agricultural Management Assistance Program (AMA)
The Agricultural Management Assistance program helps agricultural producers
manage financial risk through diversification, marketing, or natural resource
conservation practices. NRCS administers the conservation provisions while the
Agricultural Marketing Service and the Risk Management Agency implement the
production diversification and marketing provisions.
Environmental Quality Incentives Program (EQIP)
The Environmental Quality Incentives Program provides financial and technical
assistance to agricultural producers to address natural resource concerns and delivers
environmental benefits. The objectives include improving water and air quality,
conserving ground- and surface water, increasing soil health, reducing soil erosion
and sedimentation, improving or creating wildlife habitat, and mitigating against
increasing weather volatility.
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Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Conservation Stewardship Program (CSP)
The Conservation Stewardship Program helps agricultural producers maintain and
improve their existing conservation systems and adopt additional conservation
activities to address priority resource concerns. Participants earn CSP payments for
conservation performance—the higher the performance, the higher the payment.
CSP Grasslands Conservation Initiative
This new initiative helps producers protect grazing land use, conserving and improving
soil, water, and wildlife resources; and achieving related conservation values by
conserving eligible land through grassland conservation contracts. Eligible lands are
limited to cropland for which base acres have been maintained under the Farm Service
Agency’s Agricultural Risk Coverage/Price Loss Coverage and were planted to grass
or pasture, including idle or fallow, during a specific period. Enrolled acreage must be
managed consistently with a grassland conservation plan. Producers will have a single
opportunity to enroll eligible land in a 5-year contract.
Healthy Forests Reserve Program (HFRP)
The Healthy Forests Reserve Program helps landowners restore, enhance, and protect
forest land resources on private and tribal lands through easements and financial
assistance. Through HRFP, landowners promote the recovery of endangered or
threatened species, improve plant and animal biodiversity, and enhance carbon
sequestration.
Regional Conservation Partnership Program (RCPP)
The Regional Conservation Partnership Program promotes coordination between NRCS
and its partners to deliver conservation assistance to producers and landowners. NRCS
provides support to producers through partnership agreements and RCPP conservation
program contracts.
Mangroves. (Photo courtesy of James St. John; CC BY 2.0 license)
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Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Conservation Programs Administered by the Farm Service Agency (FSA)
Biomass Crop Assistance Program (BCAP)
The Biomass Crop Assistance Program provides incentives to help farmers grow
bioenergy feedstocks, i.e., crops well suited for conversion to energy such as warm-
season grasses and woody trees and shrubs.
Conservation Reserve Program (CRP)
The CRP was established in 1985 as part of the Farm Bill and is managed by the USDA’s
Farm Service Agency in collaboration with State agencies. The CRP assists landowners
in taking farmland out of agricultural production. Farmers receive funding from
the CRP to establish native vegetation on these lands and implement various land
management practices that enhance the ecosystem services of the land as a natural
habitat. Land can be enrolled in a 10- to 15-year CRP contract. CRP designates different
conservation practices that target specific environmental outcomes and specify which
vegetation types must be planted and maintained. The CRP is federally funded only.
The CREP, a program within the CRP, is a partnership between the Federal Government
and State governments. Other non-governmental groups may also contribute
funding to CREP. Landowners receive payments for part of the cost of establishing
the conservation measure and annual rental payments while the land is enrolled in
the program. When the contract expires, the land can be placed back into agricultural
production, or the contract can be renewed for another 10–15 years with State approval.
This program does not guarantee that these restored ecosystems remain in perpetuity.
Research has shown that the number of acres enrolled in this program fluctuates with
the crop price market, and farmers will take marginal lands out of CRP if they feel the
payments are too low. However, farmers are not likely to attempt to put lands heavily
affected by saltwater intrusion back into agricultural production. CRP/CREP may
provide a right way for farmers to transition their lands out of production and into a
more permanent conservation easement.
Emergency Conservation Program (ECP)
The ECP provides funding and technical assistance for farmers and ranchers to
restore farmland damaged by natural disasters and for emergency water conservation
measures in severe droughts.
Emergency Forest Restoration Program (EFRP)
The EFRP provides funding to restore privately owned forests damaged by natural
disasters.
Tree Assistance Program (TAP)
The TAP provides financial cost-share assistance to qualifying orchardists and nursery
tree growers to replant or rehabilitate eligible trees, bushes, and vines damaged by or
lost due to a natural disaster.
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Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Salinization Manual Glossary
Adsorb, Adsorption: The process by which atoms, molecules, or ions are taken up from
the soil solution or soil atmosphere and retained on the surfaces of solids by chemical
or physical binding.
Adaptation: The alteration or adjustment of land management strategies to better
function under new environmental stressors.
Alkali Soil: See Sodic Soil.
Altered Drainage: Soils that have had some modification to their natural drainage
condition.
Alkalinity: Refers to the ability or inability of water to neutralize acids. The alkalinity of
the soil is measured by pH (potential hydrogen ions).
Alkalinization: The process of becoming alkaline, i.e, increasing in pH.
Anions: An element or molecule with a negative charge. This negative charge occurs
when the number of electrons in the atom or molecule exceeds the number of protons.
Anthropogenic: The influence of human beings on nature.
Atmospheres (atm): The force exerted by the atmosphere measured at sea level. One
atmosphere equals 14.7 pounds per square inch, or one bar.
Available Water Capacity (AWC): The portion of water in a soil that can be readily
absorbed by plant roots of most crops, expressed in inches per inch, inches per foot,
or total inches for a specific soil depth. AWC is the amount of water stored in the
soil between field capacity (FC) and permanent wilting point (WP). AWC is typically
adjusted for salinity (electrical conductivity) and rock fragment content. Also called
available water holding capacity (AWC).
Available Soil Water: The difference between the actual water content of soil and the
water held by that soil at the permanent wilting point.
Bars: One bar equals 0.9869 atmospheres of pressure. For field use, the units of bars and
atmospheres are interchangeable.
Biochar: Charcoal produced from partially burned plant matter and stored in the soil as
a means of adding organic matter to the soil.
Brine: Precipitates left after highly saline water has evaporated.
Capillary Water: Water held in the capillary or small pores of the soil, usually with soil
water pressure (tension) greater than 1/3 bar. Capillary water can move in any direction.
Capillary Action: Flow of water through soil micropores in unsaturated soil due to
adhesive and cohesive forces. Capillary action is the process by which most soil water
moves to plant roots. (See Capillary Forces)
Capillary Forces: The two types of forces that cause capillary flow are adhesion and
cohesion. Adhesion is the attraction of liquid (water) molecules to solid (soil) surfaces.
Cohesion is the attraction of liquid (water) molecules to each other. Adhesive forces act
in the direction from wet soil to drier soil in unsaturated conditions. In unsaturated
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Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
soils, if the adhesive forces in the upward direction exceed the force of gravity, water
molecules are able to move upward. In saturated soils, adhesive forces are zero, and
water moves under the influence of gravity.
Cation Exchange Capacity (CEC): The sum of exchangeable cations (usually Ca, Mg, K,
Na, Al, H) that the soil constituent or other material can adsorb at a specific pH, usually
expressed in centimoles of charge per Kg of exchanger (cmol Kg
-1
), or milliequivalents
per 100 grams of soil at neutrality, or pH=0.7 (meq 100g
-1
). There are several laboratory
procedures by which CEC is estimated.
Cations: An isotope, or a compound with a positive charge.
Cohesive Forces: The attractive force between the molecules of the liquid.
Conservation Practices: Specific land management practices that control runoff of
sediment and nutrients and protect soil and water quality. Also referred to as best
management practices (BMPs).
Crop Rooting Depth: Crop rooting depth is typically taken as the soil depth containing
80 percent of plant roots, measured in feet or inches.
Datum: A base elevation used as a reference point. In soil-plant-water relations, the
datum is a horizontal reference. The datum is usually set at a depth below the root zone
such that the downward movement of water within the root zone always results in a
decrease of potential.
DeciSiemens Per Meter (dS m
-1
): A unit for electrical conductance used in evaluating
soil salinity. One deciSiemen per meter is equivalent to one millimho per centimeter.
Millimhos per centimeter were formerly used as the unit for reporting electrical
conductance of soils.
Deep Percolation (DP): Water that moves downward through the soil profile below the
plant root zone and is not available for plant use. It is a major source of groundwater
pollution in some areas.
Degradation: Displacement of soil material by water and wind; in-situ deterioration by
physical, chemical, and biological processes. This process describes human-induced
phenomena which lower the current and/or future capacity of the soil to support
human life.
Electrical Conductivity (EC): A measure of the ability of the soil water to transfer
an electrical charge. Used as an indicator for the estimation of salt concentration,
measured in mmhos cm
-1
(dS m
-1
), at 77 °F (25 °C).
Emitter: A small device that controls the irrigation water flow going to the soil.
Emitters (also known as “drippers”) come in many different flow rates and styles.
Epidermal Cells: The outer layer of cells. On a leaf, the epidermis is covered with a waxy
substance to prevent water loss.
Equivalent, or Equivalent Weight: The atomic weight or formula weight of a substance
divided by its valence. The amount of a substance in grams numerically equivalent to
its equivalent weight is one gram equivalent weight. (See Milliequivalents)
Evaporation: The physical process by which a liquid is transformed to the gaseous state,
which in irrigation generally is restricted to the change of water from liquid to vapor.
This process occurs from the plant leaf surface, ground surface, water surface, and
sprinkler spray.
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Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Evapotranspiration (ET): The combination of water transpired from vegetation and
evaporated from soil and plant surfaces. Sometimes called consumptive use (CU).
Exchange Capacity: The total ionic charge of the absorption complex active in the
adsorption of ions. See Cation Exchange Capacity (CEC).
Exchangeable Cation: A positively charged ion held on or near the surface of a solid
particle by a negative surface charge of a colloid, and which may be replaced by other
positively charged ions in the soil solution.
Exchangeable Sodium Percentage (ESP): The fraction of the cation exchange capacity of
a soil occupied by sodium ions, expressed as a percentage: exchangeable sodium (meq
100 gram soil
-1
) divided by CEC (meq 100 gram soil
-1
) times 100. ESP is unreliable in
soil containing soluble sodium silicate minerals or large amounts of sodium chloride.
Fallow: The 6- to 18-month process of replenishing soil moisture by not planting field
crops or disturbing the soil.
Field Capacity (FC): The amount of water retained after saturated soil has drained freely
by gravity. FC can be expressed as inches, inches per inch bars suction, or percent of
total available water.
Free Water: The water in the soil that is not held by adhesive forces. Also called
gravitational water, it is the water in the soil between saturation and field capacity.
Free Drainage, or Free Water Drainage: Movement of free water by gravitational forces
through and below the plant root zone. This water is unavailable for plant use except
while passing through the soil. (See Deep Percolation)
Fugitive Dust: A nonpoint source air pollution—small airborne particles that do not
originate from a specific point such as a gravel quarry or grain mill. Fugitive dust
originates in small quantities over large areas. Significant sources include unpaved
roads, agricultural cropland, and construction sites.
Geomorphology: The academic study of features found and processes operating upon
the surface of the Earth.
Glycophytes: Non-halophytic plants or plants that do not grow well when the osmotic
pressure of the soil solution rises above 2 bars.
Gravitational Water: Water in the soil that moves under the force of gravity.
Gravitational forces exceed the adhesive forces that attract water to the soil. Generally,
the water in a soil with a matric potential greater than negative 1/3 bar (water with
matric potential between that for field capacity and full saturation).
Gravity Potential, or Gravitational Potential: Potential energy of water expressed as a
distance above or below a reference line or datum. The gravitational component of soil-
water potential acts in a downward direction and is the major component of soil-water
potential for saturated conditions.
Groundwater: Water occurring in the zone of saturation in an aquifer or soil.
Gypsum: A rock-forming mineral chemically comprised of calcium sulfate dihydrate
(CaSO
4
2H
2
0). Available commercially, this product can be used to reduce sodium (Na
+
)
by replacing soil exchange sites with Ca
++
, which is a plant nutrient.
Halophytes: Defined as rooted seed-bearing plants (i.e., grasses, succulents, herbs,
shrubs, and trees) that grow in a wide variety of saline habitats from coastal dunes,
saltmarshes, and mudflats to inland deserts, salt flats, and steppes. Halophytes
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Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
can sequester sodium ions in vacuoles (pockets) within the cell by active transport
mechanisms and intracellular pumps that help maintain constant levels of salt within
the cytoplasm. This inhibits ion toxicity and helps maintain cell turgor (rigidity) while
slight accumulations of water, potassium, and manufactured organic proteins (i.e.,
proline, mannitol, sucrose, and glycine betaine) keep the cell sap from dehydrating
and allow for the proper function of essential metabolic processes. Increased protein
production, which requires additional carbon synthesis, is a direct response to the
increased salt content and changing osmotic requirements of the cell.
Hardness: The concentrations of calcium and magnesium ions expressed in terms of
calcium carbonate.
Homogeneous: Of uniform structure or composition throughout the material.
Humid Climates: Climate characterized by high rainfall and low evaporation potential.
A region generally is considered humid when precipitation averages >40 inches (1,000
mm) per year.
Humus: Organic matter. Decomposed organic compounds in soil excluding undecayed
or partially decayed plant and animal tissues and excluding the soil biomass (roots and
soil organisms).
Hydraulic Conductivity (K): The ability of a soil to transmit water flow through the
soil by a unit hydraulic gradient. Hydraulic conductivity is the coefficient k in Darcy’s
Law. Darcy’s Law is used to express flux density (volume of water flowing through a
unit cross-sectional area per unit of time). Hydraulic conductivity is usually expressed
in length per time (velocity) units (i.e., cm s
-1
, ft d
-1
). In Darcy’s Law, where V = ki, k is
established for a gradient of one. Sometimes called permeability.
Hydrostatic Pressure: The pressure at a specified water depth that is the result of the
weight of the overlying column of water.
Hypersalinity: Concentration of dissolved mineral salts such as cations Na, Ca, Mg, K,
and the major anions of Cl, SO
4
, HCO
3
, CO
3
, and NO
3
, including B, Sr
2
, SiO
2
, Mo, Ba,
and Al. This is measured as mg L
-1
.
Infiltration, Infiltration Rate: The downward flow of water into the soil at the air-soil
interface. Water enters the soil through pores, cracks, wormholes, decayed-root holes,
and cavities introduced by tillage. The rate at which water enters soil is called the
intake rate or infiltration rate.
Intake Rate: The rate at which irrigation water enters the soil at the surface. Expressed
as inches per hour. (See Infiltration)
Interception: That fraction of water from precipitation or an irrigation system captured
on the vegetation and prevented from reaching the soil surface.
Infiltration: Entry of rainwater or irrigation water into the soil at the soil-atmosphere
interface.
Interflow: The flow of groundwater in the lateral direction from one aquifer (usually a
perched aquifer) to another aquifer of lower elevation.
Interveinal Chlorosis: A yellowing or bleaching effect of cells in leaf structure between
the veins that move photosynthates through the plant.
In-situ: In its original place, unmoved, unexcavated, remaining at the site, or in the
subsurface.
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Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Ion: An atom or group of atoms that has an electric charge due to an imbalance in
the number of protons and electrons. If protons outnumber electrons, the charge is
positive; if electrons outnumber protons, the charge is negative. (See also Cation and
Anion)
Ionic Concentration: The amount of solute in a water body or water sample.
Concentrations of ions are usually expressed in milligrams per liter, milliequivalents
per liter, or in parts per million.
Leaching Fraction (L
f
): The ratio of the depth of subsurface drainage water (deep
percolation) to the depth of infiltrated irrigation water. (See Leaching Requirement)
Leaching Requirement: (1) The amount of irrigation water required to pass through the
plant root zone to reduce the salt concentration in the soil for reclamation purposes.
(2) The fraction of water from irrigation or rainfall required to pass through the soil to
prevent salt accumulation in the plant root zone and sustain production. (See Leaching
Fraction)
Leaching: Removal of soluble material from soil or other permeable material by the
passage of water through it.
Macropores: Secondary soil features such as root holes or desiccation cracks that can
create significant conduits for the movement of non-aqueous phase liquids (NAPL) and
dissolved contaminants, or vapor-phase contaminants.
Matric Potential: A dynamic soil property that will be near zero for a saturated soil.
Matric potential results from capillary and adsorption forces. Formerly called capillary
potential or capillary water.
Mesophytic: Land plant growing in surroundings having an average supply of water;
compare xerophyte and hydrophyte.
Micropore: Smaller soil pores through which water can move by capillary forces. (See
Macropores)
Milliequivalent: 1/1000 of one gram equivalent weight. (See Equivalent Weight)
Millimoles: One one-thousandth of a gram-mole.
Millimhos: Older reference designation of mmhos cm
-1
of electrical conductivity of soil
paste extract.
Milligram Per Liter: A unit of concentration for water quality reports. For water, one
milligram per liter is essentially equivalent to one part per million.
Mitigation: Short-term strategy to lessen the impact or damage from environmental
stresses such as drought, flooding, saltwater impacts, etc.
Monovalent: An element or compound with an electric charge of plus or minus one.
Potassium, hydrogen, and sodium are examples.
Necrosis: Unprogrammed death of cells/living tissue.
Non-Saline Sodic Soil: A soil containing soluble salts that provide electrical
conductivity of the saturation extract (ECe) <4.0 mmhos cm
-1
and an exchangeable
sodium percentage (ESP) >15. Commonly called black alkali or slick spots.
Osmotic Potential, or Solute Potential: Arises because of soluble materials (generally
salts) in the soil solution and the presence of a semi-permeable membrane. Osmotic
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Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
potential is the force exerted across the semi-permeable membrane due to differing
concentrations of salts on each side.
Orthophotography: The ortho process corrects for distortions caused by the terrain, the
orientation of the airplane, and the camera lens. An orthoimage is like a photo that has
been draped over the ground over an uneven surface. The ground is represented by an
elevation model. Orthophotography is a product that has the geometric accuracy of a
map but contains the immense detail of a photograph.
Overburden Potential: The pressure due to the weight the soil exerts on the water in the
soil. Overburden potential is zero for unsaturated conditions.
Parts Per Million (ppm): A unit of concentration for water quality reports. For water, one
part per million is approximately equivalent to one milligram per liter.
Percolation: Movement of the water through the soil profile. The percolation rate is
governed by the permeability or hydraulic conductivity of the soil. Both terms are used
to describe the ease with which soil transmits water.
Permanent Wilting Point (PWP): The moisture percentage, on a dry weight basis, at
which plants can no longer obtain sufficient moisture from the soil to satisfy water
requirements. Plants will not fully recover when water is added to the crop root zone
once the permanent wilting point has been experienced. Classically, 15 atmospheres (15
bars), or 1.5 mPa, soil moisture tension is used to estimate PWP.
Permeability: (1) Qualitatively, the ease with which gases, liquids, or plant roots
penetrate or pass through a layer of soil. (2) Quantitatively, the specific soil property
designating the rate at which gases and liquids can flow through the soil or porous
media.
Permeameter: An instrument for rapidly measuring the permeability of a sample
of iron or steel with sufficient accuracy for many commercial purposes. A constant
head permeameter that measures in-situ hydraulic conductivity. The method involves
measuring the steady-state rate of water recharge into unsaturated soil from a 2-inch
cylindrical hole, in which a constant head of water is maintained.
Piezometer: An open-ended tube inserted into the soil for measuring pressure potential.
Plant Available Water (PAW): Water available in the soil for plant use, the difference
between field capacity (FC) and wilting point (WP).
Plant Biomass: The top growth or vegetative (leafy) portion of the plant. This material
is grazed by livestock when green (forage) but can be harvested and used after
senescence (residue) to create heat from burning, as animal bedding, or as a component
of erosion control products.
Pressure Potential: A component of soil-water potential, represented by the distance of
submergence. For unsaturated conditions, pressure potential is zero.
Primordial: Having existed from the beginning; in an earliest or original stage or state.
Rhizosphere: The region of the soil immediately surrounding the roots.
Root Zone: Depth of soil that plant roots readily penetrate and in which the
predominant root activity occurs. The preferred term is the plant root zone.
Runoff, Runoff Loss: Surface water leaving a field or farm, resulting from surface
irrigation tailwater, applying water with sprinklers at a rate higher than soil infiltration
and surface storage, overirrigation, and precipitation.
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Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
SAR: Measures the relative proportion of sodium ions in a soil or water sample to
those of calcium and magnesium. A relation between soluble sodium and soluble
divalent cations that can be used to predict the exchangeable sodium percentage of soil
equilibrated with a given solution.
Saline Soil: A non-sodic soil containing sufficient soluble salts to impair its
productivity for growing most crops. The electrical conductivity of the saturation
extract (ECe) is >4 mmhos cm
-1
, and the exchangeable sodium percentage (ESP) is <15
(i.e., non-sodic). The principal ions are chloride, sulfate, small amounts of bicarbonate,
and occasionally some nitrate. Sensitive plants are affected at half this salinity, and
highly tolerant ones at about twice this salinity.
Saline-Sodic Soil: Soil containing both sufficient soluble salts and exchangeable
sodium to interfere with the growth of most crops. The exchangeable sodium
percentage (ESP) is ≥15, and the electrical conductivity of the saturation extract (ECe)
is >4 mmhos cm
-1
. Saline-sodic soil is difficult to leach because the clay colloids are
dispersed.
Salinity: The concentration of dissolved mineral salt in water and soil on a unit volume
or weight basis. May be harmful or nonharmful for the intended use of the water.
Salinization: The process of a building up of salts in soil eventually to toxic levels.
Saltwater Intrusion: The process of saltwater infiltrating groundwater/aquifer systems.
Saltwater Inundation: Surface water impacts from saltwater related to sea-level rise and
coastal storm flooding.
Satiation: To fill most voids between soil particles with water.
Saturation: To fill all (100 percent) voids between soil particles with water.
Saturated Hydraulic Conductivity: A quantitative measure of a saturated soil’s
ability to transmit water when subjected to a hydraulic gradient. Saturated hydraulic
conductivity can be thought of as the ease with which pores of a saturated soil permit
water movement.
Solute: The dissolved substance in a solution (water).
Soil Aeration: Process by which air and other gases enter the soil or are exchanged.
Soil Crusting: Compaction of the soil surface by droplet impact from sprinkle irrigation
and precipitation. Well-graded, medium textured, low organic matter soils tend to crust
more readily than other soils.
Soil Horizon: A layer of soil differing from adjacent genetically related layers in
physical, chemical, and biological properties or characteristics.
Soil Moisture Tension: See Soil-Water Tension.
Soil Organic Matter: Organic fraction of the soil, including plant and animal residue
in various stages of decomposition, cells, and tissues of soil organisms, and substances
synthesized by the soil population.
Soil pH: is a measure of the hydrogen ion concentration in soil solution and represents
the chemical status of the soil. The soil pH scale ranges from 0 to 14; pH=7 is neutral,
pH <7 is acidic, and pH >7 is alkaline or basic. Many arable soils have a pH in the range
of 6.0–7.0.
Soil Profile: Vertical section of the soil from the surface through all its horizons.
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Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Soil Resilience: The ability of a soil to maintain some level of productivity after being
exposed to negative environmental stressors.
Soil Sealing: The orientation and consolidation of soil particles in the intermediate
surface layer of soil so that the layer of soil becomes almost impermeable to water.
Soil Structure: The combination or arrangement of primary soil particles into
secondary particles, units, or peds that make up the soil mass. These secondary
units may be arranged in the soil profile in such a manner as to give a distinctive
characteristic pattern. Principal types of soil structure are platy, prismatic, columnar,
blocky, granular, and massive.
Soil Texture: Classification of soil by the relative proportions of sand, silt, and clay
present in the soil. USDA uses 12 textural classes.
Soil Water, Soil Moisture: All water stored in the soil. (See Water Holding Capacity)
Soil-Water Content: The water content of a given volume of soil. Soil-water content is
determined by gravimetric sampling and oven drying field samples (to a standard
105 °C), neutron moisture probes, time-domain (TDR) and frequency domain
reflectometry (FDR) devices commonly called RF capacitance probes, tensiometers,
electrical resistance blocks, thermal dissipation blocks, and feel and appearance methods.
Soil-Water Deficit or Depletion: Amount of water required to raise the soil-water content
of the crop root zone to field capacity. The amount of water is measured in inches.
Soil-Water Potential: Expresses the potential energy status of soil water relative to
conditions associated with pure, free water. Total soil-water potential consists of
osmotic potential, gravitational potential, and matric potential.
Soil-Water Tension: A measure of the tenacity with which water is retained in the soil.
Soil-water tension is the force per unit area that must be exerted to remove water from
the soil and is usually measured in bars or atmospheres. Soil-water tension is a measure
of the effort required by plant roots to extract water from the soil. Measurements are
made using a tensiometer in the field (limited to 1 atm) and a pressure plate apparatus
in the laboratory.
Specialty Crop: A unique or locally grown crop, usually grown on smaller acreages, that
has a niche market.
Specific Conductance: A measure of how well water can conduct electrical current for
a unit length and unit cross-section at a certain temperature. Expressed in units of
milliSiemens per centimeter (mS∙cm
-1
), the conductivity normalized to a temperature
of 25 °C.
Subhumid Climate: Climate characterized by a moderate rainfall and moderate to high
evaporation potential. A region is usually considered subhumid when precipitation
averages >20 inches (500 mm) per year, but <40 inches (1,000 mm) per year.
Sulfidation: A process of increasing sulfide ions in a material or molecule.
Stoma [pl. Stomata]: An opening or pore, usually in plant leaves, that provides access
for gaseous exchange between the tissues and the atmosphere.
Tensiometer: Instrument, consisting of a porous cup filled with water and connected to
a manometer or vacuum gauge, used for measuring the soil-water matric potential.
Terrestrial Systems: The interactions between soil, water, vegetation, and the
atmosphere take place in the unsaturated soil layers.
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Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
Total Dissolved Solids (TDS): The total dissolved mineral constituents of water.
Translocation: Movement of water from an area other than where the water was
applied.
Transpiration: The process of plant water uptake and use, beginning with
absorption through the roots and ending with transpiration at the leaf surfaces. (See
Evapotranspiration)
Unavailable Soil Water: That portion of water in soil held so tightly by adhesion and
other soil forces that the water cannot be absorbed by plants rapidly enough to sustain
growth without permanent damage. The soil water remaining at the permanent wilting
point of plants.
Tortuous Path: The non-straight nature of soil pores.
Total Soil-Water Potential: See Soil-Water Potential.
Transpiration: The movement of water through plant tissues and into the atmosphere.
(See Evapotranspiration)
Unsaturated Soil: Soil in which air exists in the soil pore spaces.
Vadose Zone: The unsaturated zone in a soil where chemical processes are at their most
active.
Viscosity: Refers to the quality of a liquid being thick and slow-to-flow. For instance,
cold honey has a much higher viscosity than water.
Water Holding Capacity: Total amount of water held in the soil per increment of depth.
Water holding capacity is the amount of water held between field capacity (FC) and
oven-dry moisture level, expressed in inches per inch, inches per foot, or total inches for
a specific soil depth. Soils that are not freely drained because they have impermeable
layers can have temporary saturated conditions just above the impermeable layers. This
can temporarily increase water holding capacity. Sometimes called total water holding
capacity. (See Available Water Capacity)
Wilting Point: See Permanent Wilting Point.
Soil affected by high salinity. (Photo courtesy of IFPRI; CC BY-NC-ND 2.0 license)
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Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
References
1. Gedan, K.B.; Epanchin-Niell, R.; Qi, M. 2020. Rapid land cover change in a
submerging coastal county. Wetlands. https://doi.org/10.1007/s13157-020-01328-y.
2. Sweet, W.; Park, J.; Marra, J. [et al.]. 2014. Sea level rise and nuisance flood frequency
changes around the United States. NOAA Tech. Rep. NOS CO-OPS 073 58.
3. Church, J.A.; White, N.J. 2006. A 20th century acceleration in global sea-level rise.
Geophysical Reseach Letters. 33: 94-97. https://doi.org/10.1029/2005GL024826.
4. Fagherazzi, S.; Anisfeld, S.C.; Blum, L.K. [et al.]. 2019. Sea level rise and the
dynamics of the marsh-upland boundary. Frontiers in Environmental Science.
7: 1-18. https://doi.org/10.3389/fenvs.2019.00025.
5. Sallenger, A.H.; Doran, K.S.; Howd, P.A. 2012. Hotspot of accelerated sea-level
rise on the Atlantic Coast of North America. Nature Climate Change. 2: 884-888.
https://doi.org/10.1038/nclimate1597.
6. Maas, E.V.; Grattan, S.R. 1999. Crop yields as affected by salinity. Agricultural
Drainage. 38: 55–108. Agronomy Monographs, Chapter 3. https://doi.org/10.2134/
agronmonogr38.c3.
7. NCRS. 1996. Plant materials for saline-alkaline soils. Technical Notes—Plant
Materials No. 26-96-MT-26 (Revised). Bridger, MT: U.S. Department of Agriculture
Natural Resources Conservation Service. 5 p. (ID#13126). Available at: https://www.
nrcs.usda.gov/Internet/FSE_PLANTMATERIALS/publications/mtpmstn13126.pdf.
[Date last accessed: November 2020].
8. Conway, T. 2001. Plant materials and techniques for brine site reclamation. Plant
Materials Technical Note No. 26. 7 p. Available at: https://www.nrcs.usda.gov/
Internet/FSE_PLANTMATERIALS/publications/kspmstn260201.pdf. [Date last
accessed: November 2020].
9. McGeorge, W.T. 1954. Diagnosis and improvement of saline and alkaline soils.
Soil Science Society of America Journal. 18(3): 348. https://doi.org/10.2136/
sssaj1954.03615995001800030032x.
10. Pezeshki, S.R.; Delaune, R.D.; Patrick, W.H. 1990. Flooding and saltwater
intrusion: Potential effects on survival and productivity of wetland forests along
the U.S. Gulf Coast. Forest Ecology and Management. 33-34: 287-301. https://doi.
org/10.1016/0378-1127(90)90199-L.
11. Conner, W.H.; Mcleod, K.W.; McCarron, J.K. 1997. Flooding and salinity effects on
growth and survival of four common forested wetland species. Wetlands Ecology
and Management. 5: 99-109. https://doi.org/10.1023/A:1008251127131.
12. Hoeppner, S.S.; Shaffer, G.P.; Perkins, T.E. 2008. Through droughts and hurricanes:
Tree mortality, forest structure, and biomass production in a coastal swamp
targeted for restoration in the Mississippi River Deltaic Plain. Forest Ecology and
Management. 256(5): 937-948. https://doi.org/10.1016/j.foreco.2008.05.040.
67
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
13. Tully, K. et al. 2019. The invisible flood: The chemistry, ecology, and social
implications of coastal saltwater intrusion. Bioscience. 69(5): 368-378. https://doi.
org/10.1093/biosci/biz027.
14. Twidwell, E.; Stevens, J.C. 2006. Dealing with saltwater intrusion in pastures and
hayfields. Disaster Information Resources. LSU AgCenter Research and Extension.
Available at: https://www.lsuagcenter.com/~/media/system/2/a/4/e/2a4eb08ad0d
950023c822b5a9122b295/pub2949epasturesaltwaterintrusionfinal.pdf. [Date last
accessed: November 2020].
15. NRCS. 2017. Potential mobility of road salt. Soil survey of the State of
Connecticut—Interpretations [web site]. U.S. Department of Agriculture, Natural
Resources Conservation Service. 19 p. Available at: https://www.nrcs.usda.gov/wps/
portal/nrcs/detail/ct/soils/?cid=stelprdb1143068. [Date last accessed: November
2020].
16. Chessman, D.; Moebius-Clune, B.N.; Smith, B.R.; Fisher, B. 2019. The basics of
addressing resource concerns with conservation practices within integrated soil
health management systems on cropland. Soil Health Technical Note No. 450-04.
U.S. Department of Agriculture, Natural Resources Conservation Service. [Not
paged].
17. U.S. Department of Agriculture, Natural Resources Conservation Service (USDA-
NRCS). [No date]. Conservation practice standards. In: NRCS online Field Office
Technical Guide. Available at https://efotg.sc.egov.usda.gov/. [Date last accessed:
November 2020].
18. Alldred, M.; Baines, S.B.; Findlay, S. 2016. Effects of invasive-plant management
on nitrogen-removal services in freshwater tidal marshes. PLoS One. 11: e0149813.
https://doi.org/10.1371/journal.pone.0149813.
19. U.S. Army Corps of Engineers (USACE). 2014. Procedures to evaluate sea level
change: impacts, responses, and adaptation. Technical Letter. 1100-2-1: 254.
Available at: https://www.publications.usace.army.mil/Portals/76/Publications/
EngineerTechnicalLetters/ETL_1100-2-1.pdf. [Date last accessed: November 2020].
20. Maloney, M.C.; Preston, B. L. 2014. A geospatial dataset for U.S. hurricane storm
surge and sea-level rise vulnerability: Development and case study applications.
Climate Risk Management. 2: 26-41. https://doi.org/10.1016/j.crm.2014.02.004.
21. Bell, G.D.; Blake, E.S.; Landsea, C.W. [et al.]. 2012. Tropical cyclones-Atlantic basin.
In: Blunden, J.; Arndt, D., eds. State of the Climate in 2011. Bulletin of the American
Meteorological Society. 93: S99-S105.
22. McNulty, S.; Baca, A.; Bowker, M. [et al.]. 2019. Managing effects of drought in the
Southeast United States. In: Vose, J.M.; Peterson, D.L.; Luce, C.H.; Patel-Weynand,
T., eds. Effects of drought on forests and rangelands in the United States: translating
science into management responses. Gen. Tech. Rep. WO-98. Washington, DC: U.S.
Department of Agriculture, Forest Service, Washington Office: 191-220. Chapter 9.
23. Keighton, W.B. 1966. Fresh-water discharge-salinity relations in the tidal delaware
river resh-water discharge- salinity relations in the Tidal Delaware River. Geological
Survey Water-Supply Paper 1586-G. U.S. Department of the Interior, U.S. Geological
Survey, in cooperation with the City of Philadelphia and the Delaware Geological
Survey. 16 p. Available at: https://pubs.usgs.gov/wsp/1586g/report.pdf. [Date last
accessed: November 2020].
68
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
24. Weston, N.B.; Dixon, R.E.; Joye, S.B. 2006. Ramifications of increased salinity
in tidal freshwater sediments: Geochemistry and microbial pathways of organic
matter mineralization. Journal of Geophysical Research. 111: 1-14. https://doi.
org/10.1029/2005JG000071.
25. Taillie, P.J.; Moorman, C.E.; Poulter, B. [et al.]. 2019. Decadal-scale vegetation
change driven by salinity at leading edge of rising sea level. Ecosystems. 22: 1918-
1930. https://doi.org/10.1007/s10021-019-00382-w.
26. Poulter, B.; Christensen, N.L.; Qian, S.S. 2008. Tolerance of Pinus taeda and
Pinus serotina to low salinity and flooding: Implications for equilibrium
vegetation dynamics. Journal of Vegetation Science. 19: 15-22. https://doi.
org/10.3170/2007-8-18410.
27. Teobaldelli, M.; Mencuccini, M.; Piussi, P. 2004. Water table salinity, rainfall and
water use by umbrella pine trees (Pinus pinea L.). Plant Ecology. 171: 23-33. ht t p s://
doi.org/10.1023/B:VEGE.0000029384.40192.cc.
28. McLeod, K.W.; McCarron, J.K.; Conner, W.H. 1996. Effects of flooding and salinity
on photosynthesis and water relations of four southeastern coastal plain forest
species. Wetlands Ecology and Management. 4: 31-42. https://doi.org/10.1007/
BF01876133.
29. Gabriel, J.L;, Almendros, P.; Hontoria, C.; Quemada, M. 2012. The role of cover crops
in irrigated systems: soil salinity and salt leaching. Agriculture, Ecosystems &
Environment. 158: 200-207. https://doi.org/10.1016/j.agee.2012.06.012.
30. Russelle, M.P.; Entz, M.H.; Franzluebbers, A.J. 2007. Reconsidering integrated crop-
livestock systems in North America. Agronomy Journal. 99: 325-334. https://doi.
org/10.2134/agronj2006.0139.
31. Schieder, N.W.; Kirwan, M.L. 2019. Sea-level driven acceleration in coastal forest
retreat. Geology 47: 1151-1155. https://doi.org/10.1130/G46607.1.
32. Gallagher, J.L. 1985. Halophytic crops for cultivation at seawater salinity. Plant and
Soil. 89: 323-336. https://doi.org/10.1007/978-94-009-5111-2_22.
33. NRCS. 2006. Planting and managing switchgrass as a biomass energy crop. Plant
Materials Technical Note No. 3. Available at: https://www.nrcs.usda.gov/Internet/
FSE_PLANTMATERIALS/publications/npmptn3-13079.pdf. [Date last accessed:
November 2020].
34. Liu, X.; Conner, W.H.; Song, B.; Jayakaran, A.D. 2017. Forest composition and
growth in a freshwater forested wetland community across a salinity gradient in
South Carolina, USA. Forest Ecology and Management. 389: 211-219. https://doi.
org/10.1016/j.foreco.2016.12.022.
35. USDA-ERS. 2020. Wheat sector at a glance. Available at: https://www.ers.usda.gov/
topics/crops/wheat/wheat-sector-at-a-glance. [Date last accessed: June 2020].
36. Drake, K.; Halifax, H.; Adamowicz, S.C.; Craft, C. 2015. Carbon sequestration in
tidal salt marshes of the Northeast United States. Environmental Management. 56:
998-1008. https://doi.org/10.1007/s00267-015-0568-z.
37. Brisson, C.P.; Coverdale, T.C.; Bertness, M.D. 2014. Salt marsh die-off and recovery
reveal disparity between the recovery of ecosystem structure and service provision.
Biological Conservation. 179: 1-5. https://doi.org/10.1016/j.biocon.2014.08.013.
69
Identification, Mitigation, and Adaptation to Salinization on Working Lands in the U.S. Southeast
38. Velasquez-Manoff, M. 2019. As sea levels rise, so do ghost forests. The New York
Times. Available at: https://www.nytimes.com/interactive/2019/10/08/climate/
ghost-forests.html. [Date last accessed: November 2020].
39. White, E.; Kaplan, D. 2017. Restore or retreat? Saltwater intrusion and water
management in coastal wetlands. Ecosystem Health and Sustainability. 3: 1-18.
https://doi.org/10.1002/ehs2.1258.
40. U.S. Environmental Protection Agency (US EPA). 2016. Climate change indicators
in the United States: 2016. Fourth edition. EPA 430-R-16-004. Available at: ht t ps://
www.epa.gov/sites/production/files/2016-08/documents/climate_indicators_2016.
pdf. [Date last accessed: November 2020].
41. Couvillion, B.R.; Fischer, M.R.; Beck, H.J.; Sleavin, W.J. 2016. Spatial configuration
trends in coastal Louisiana from 1985 to 2010. Wetlands. 36: 347-359. https://doi.
org/10.1007/s13157-016-0744-9.
Gibson, Nancy; McNulty, Steven; Miller, Chris; Gavazzi, Michael;
Worley, Elijah; Keesee, Dan ; and Hollinger, David. 2021.
Identification, mitigation, and adaptation to salinization on
working lands in the U.S. Southeast. Gen. Tech. Rep. SRS-259.
Asheville, NC: U.S. Department of Agriculture Forest Service,
Southern Research Station. 69 p. https://doi.org/10.2737/
SRS-GTR-259.
Key Messages:
• Soil salinization in the coastal Southeastern United States is
becoming more prevalent as storm surges increase in frequency,
and sea levels rise.
• Salinization reduces the productivity of working lands and can
prevent crops from growing.
• Resources are lacking for landowners to understand coastal
salinization and how to manage for resilience.
• Action must be taken if the land is to remain profitable as
conditions change.
This manual describes the impacts and includes adaptation
measures that can be taken to maintain productivity in working
lands.
Keywords: Adaptation, agriculture, saline soil, salinity,
salinization, sea-level rise.
www.srs.fs.usda.gov
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