Natural Resources Conservation Service
CONSERVATION PRACTICE STANDARD
AMENDING SOIL PROPERTIES WITH GYPSUM PRODUCTS
Using gypsum- (calcium sulfate dihydrate) derived products to change the physical and/or chemical properties of soil.
• Improve soil health by improving physical/chemical properties and increasing infiltration of the soil.
• Improve surface water quality by reducing dissolved phosphorus concentrations in surface runoff and subsurface drainage.
• Improve soil health by ameliorating subsoil aluminum toxicity.
• Improve water quality by reducing the potential for pathogens and other contaminants transport from areas of manure and biosolids application.
CONDITIONS WHERE PRACTICE APPLIES
• This practice applies where land application of gypsum products will be used to alter the physical and/or chemical characteristics of soil to help achieve one of the above purposes.
• To remediate sodic soils, use Conservation Practice Standard (CPS) Code 610, Salinity and Sodic Soil Management.
General Criteria Applicable to All Purposes
Do not apply gypsum products in watersheds where sulfate additions are restricted.
Validation of product.—It is the responsibility of the amendment provider to furnish chemical analysis documentation for the product to the producer. The chemical analysis documentation will include the calcium and sulfur content and content of heavy metals and all other potential contaminants listed in table 1.
Concentrations of potential contaminants cannot exceed maximum allowable concentrations listed in table 1. In addition, the radium-226 concentration in the gypsum-derived product cannot exceed 10 picocuries per gram (pCi/g).
Flue gas desulfurization (FGD) gypsum that is produced by forced-oxidation wet systems after the removal of fly ash is acceptable for these uses.
NRCS, NHCP June 2015 Conservation practice standards are reviewed periodically and updated if needed. To obtain the current version of this standard, contact your Natural Resources Conservation Service State office or visit the Field Office Technical Guide.
The prescribed minimum application rates are based on a calcium sulfate dihydrate equivalency of 100 percent. Application rates for products that are less than 100 percent calcium sulfate dihydrate equivalence should be adjusted accordingly.
|Table 1. Screening values for elements in gypsum-derived products for use as a soil amendment. Symbol (Element)||Units gram (g) kilogram (kg) milligram (mg)||Screening Value for Gypsum-Derived Products||Comment|
|Ag (Silver)||mg kg-1||…||No limit required|
|Al (Aluminum)||g kg-1||…||No limit required|
|As (Arsenic)||mg kg-1||13.1||…|
|B† (Boron)||mg kg-1||200.†||…|
|Ba (Barium)||mg kg-1||1000.||…|
|Be (Beryllium)||mg kg-1||2.5||…|
|Ca (Calcium)||g kg-1||…||Ca fertilizer; no limit required|
|Cd‡ (Cadmium)||mg kg-1||1.0||…|
|Co (Cobalt)||mg kg-1||20.||…|
|Cr(III) (Chromium)||mg kg-1||100.||…|
|Cu (Copper)||mg kg-1||95.||…|
|Fe (Iron)||g kg-1||…||No limit required|
|Hg (Mercury)||mg kg-1||2.5||…|
|Mg (Magnesium)||g kg-1||…||Mg fertilizer; no limit required|
|Mn (Manganese)||mg kg-1||1500.||…|
|Mo (Molybdenum)||mg kg-1||10.||…|
|Ni (Nickel)||mg kg-1||100.||…|
|Pb (Lead)||mg kg-1||30.||…|
|S* (Sulfur)||g kg-1||220.||S fertilizer; *limit access to ruminants|
|Sb (Antimony)||mg kg-1||1.5||…|
|Se (Selenium)||mg kg-1||50.||…|
|Sn (Tin)||mg kg-1||…||No limit required|
|Tl (Thallium)||mg kg-1||1.0||…|
|V (Vanadium)||mg kg-1||136.||…|
|Zn (Zinc)||mg kg-1||125.||…|
† Should not apply greater than 0.9 lb. hot water soluble B/acre with gypsum amendment application rate.
‡ Cd is 1% of Zn limit to restrict food-chain risks of soil Cd.
* Prevent ruminant livestock from ingesting gypsum from storage piles; prevent grazing on amended pastures until one rainfall (or irrigation) event to wash forage.