Gypsum May Save Salt Damaged Lawns

COURT HOUSE- Homeowners who had their lawns flooded with saltwater as a result of Hurricane Sandy maybe wondering how they can prevent a brown, dead lawn.
Jenny S. Carleo, agricultural and natural resource management agent for Rutgers New Jersey Agricultural Experiment Station, Cooperative Extension of Cape May County, consulted with Stephanie Murphy, director of the Soil Testing Lab at Rutgers, on the matter and recommended the following for saltwater inundated lawns:
* Get a Rutgers soil test kit from office at 355 Court House-So. Dennis Rd. in Court House or go online: http://njaes.rutgers.edu/soiltestinglab/ to determine the extent of the damage and the need for remediation.
* Ask Rutgers for the $10 salt test on the form.
* Follow the Rutgers directions on soil remediation in the report that you receive back.
* If you have questions about the results form you can call the Rutgers Master Gardeners of Cape May County at 609-465-5115.
Carleo said she received calls from homeowners and farmers with saltwater concerns. She said farmers reported death of grape vines and turf grass.
“We also had saltwater get into fresh water irrigation ponds,” said Carleo.
She said farmers have had saltwater intrusion in the past but nothing of the level produced by Hurricane Sandy.
Carleo said if there is excessive sodium in the soil it is likely that Rutgers will recommend an application of gypsum. Gypsum can be used to displace sodium from the soil. She said it requires fresh water to solubilize the gypsum and leach the sodium away, out of the root zone.
A Rutgers blog post by James Murphy, extension specialist in turf grass management and Stephanie Murphy notes saltwater will burn plant tissue, dehydrate plants caused by increased osmotic potential in soil and cause a loss of soil structure and soil infertility caused by increased soil pH (excessive alkalinity).
Testing for salt is recommended. Soil testing for “soluble salts” by electrical conductivity is a special test (typically not included with a standard fertility test) with modest additional fee of $10 at the Rutgers Soil Testing Laboratory.
Test of soil pH is part of the standard soil fertility test. Evaluation of the sodium level in soil can also be determined by an evaluation of exchangeable cations (with or without evaluation of cation exchange capacity).
The lab’s soil test reports include a brief interpretive statement along with the data. A document on the Soil Testing website has interpretations of EC values and related information: http://njaes.rutgers.edu/soiltestinglab/pdfs/ec-interpret.pdf
For finer-textured soil, it is important to add gypsum before leaching is practiced otherwise the loss of soil structure due to excess sodium could result in a waterlogged site. Gypsum (calcium) is useful because it helps to displace sodium from the soil (exchange sites).
Gypsum should be finely ground and well mixed into topsoil for best results. Gypsum is moderately soluble (dissolves slowly), and its solubility is actually enhanced by the presence of salt. Therefore, apply 1 to 2 ton per acre if gypsum can be mixed into the root zone; otherwise make multiple applications of gypsum in smaller amounts before leaching (heavy rain or irrigation) events.
Excess sodium is problematic because it destroys soil structure. Excess sodium disperses the small soil particles (colloids), which can then clog soil pores and inhibit drainage and leaching.
This may not be a critical factor in the case of many coastal soils (sands, loamy sands) since very sandy soils are “single-grained” and lack the small particles (clay and organic matter) that can be dispersed and clog pores. However, tidal river floodplains (including the inner coastal plain) will have finer textured soils that will be adversely affected by excess sodium inhibit drainage and leaching.
Elemental sulfur is an effective alternative to gypsum in calcareous (high pH) soils/sands such as those with high shell (calcium carbonate) content. Sulfur is converted by bacteria in soil) into sulfuric acid which reacts with shells calcium carbonate to produce calcium. The calcium is then available to help displace and leach sodium from the soil, which improves soil permeability and reduces the hazards of sodium. Sulfur amendment is not as widely available as gypsum, so you may have to make a special request from a supplier should you need to treat a calcareous soil.
You should expect damage to cool season grasses that were inundated by saltwater flooding. Of the most common turf grasses grown in New Jersey, annual bluegrass, rough bluegrass, colonial bent grass, some Kentucky bluegrasses, and some creeping bent grasses will be the most sensitive to salinity. Most fine fescue species as well as some Kentucky bluegrasses and some creeping bent grasses are thought to be moderately tolerant of salinity.
Perennial ryegrass, slender creeping red fescue, and tall fescue are generally considered to have the best tolerance to salinity of the cool season turf grasses that are commonly grown in our region.
If you need to assess whether the turf is dead or dormant, you can simply remove a core or spade full of sod (turf and soil) from the site of interest and place it in a planting pot or pan containing some good (not salt-affected) potting mix.
Place the replanted sod sample in a warm (65 to 75 degrees) sunny location and water. Water to leach excess salts out of the soil and potting mix; you may want to lightly sprinkle gypsum over the sod before watering. New leaves should start to regrow from the damage piece of sod within a week or so if the plants have not died.
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