Ohio farmers and university researchers have experimented with gypsum as a source of crop nutrients and as a tool to increase water infiltration, decrease erosion, expand rooting and reduce nutrient losses.

Some results indicate that application of gypsum may improve soil structure and help to prevent compaction and problems with runoff, ponding and erosion on certain types of soils.

Gypsum or calcium sulfate (CaSO4) is one of the earliest forms of fertilizer used in the United States. Gypsum amendments can improve the physical and chemical properties of soils, thus reducing erosion losses of soils and nutrient concentrations – especially phosphorus – in surface water runoff.

It is important to note that pure gypsum is not a liming agent, and it cannot be used to raise soil pH, since both calcium and sulfur are released. However, gypsum has the potential to relieve aluminum (Al3+) toxicity in acid soils and to supply calcium and sulfur (S) for plant nutrition.

Gypsum contains about 20 percent calcium and 16 percent sulfur in sulfate form on a dry matter basis, however nutrient values vary depending on the specific source of the product.

Beyond providing valuable nutrients, soil scientists have observed gypsum can improve the physical properties of certain soils, particularly those with high clay content. The calcium in gypsum helps to build soil aggregates and create pore spaces within the soil profile.

Ohio State University researchers have studied gypsum’s impact on water quality http://southcenters.osu.edu/soil- and-bioenergy and http://agnr.osu.edu/ news/fall-gypsum-applications-improve- soil-increase-sulfur-and-calcium-next- crop

In a study at multiple commercial sites, the Ohio researchers are demonstrating gypsum reduces soluble phosphorus concentrations in tile water runoff. In the first two years of the ongoing study, farm fields treated with gypsum had an average 55-percent reduction in soluble phosphorus concentrations based on tests of water samples collected from field drainage tiles

For news on the use of gypsum to improve soils, there a number of fact sheets from OSU at http://fabe.osu.edu/ sites/fabe/files/imce/files/Soybean/ Gypsum%20Bulletin.pdf and a fact sheet located at http://ohioline.osu.edu/anr- fact/0020.html

Ohio farmers wishing to use gypsum to improve soil quality now have access to USDA technical information and possible financial assistance through their local Natural Resources Conservation Service (NRCS) office.

Ohio and Indiana’s state NRCS technical staff recently adopted an interim practice standard providing guidelines for how gypsum can be incorporated as part of various conservation programs including the Environmental Quality Incentives Program (EQIP).

"An interim standard is put in place for a new conservation practice and used generally for 3-5 years during which time the practice will be evaluated for both its effectiveness as a practice and its effectiveness when used as part of a conservation system," said Chris Coulon, public affairs specialist for Ohio NRCS.

The Ohio practice standard stipulates qualified gypsum applications must be used to alter the physical or chemical characteristics of soil to help achieve one of the program purposes. In addition to technical information, the new standard spells out NRCS financial assistance options for gypsum applications.

In Ohio, approved growers are eligible to apply to receive approximately $21 to $36 per acre depending on the application rate.

For Ohio growers that operate in the Western Lake Erie Basin watershed, additional incentives may also be available through the Regional Conservation Partnership Program grants as part of the Tri-State Western Lake Erie Basin Phosphorus Reduction Initiative.

For more about using gypsum as part of on-farm conservation programs, visit an Ohio NRCS office, www.nrcs.usda. gov/wps/portal/nrcs/sitenav/national/ states or find links to NRCS documents at www.gypsoil.com/conservation

Those interested in learning more about the gypsum and soil quality research being performed or if you would like to join our Horticulture or Soil and Water resources email lists visit the OSU South Centers website http://southcenters.osu. edu or contact Horticulture Specialist and Extension Educator Brad Bergefurd, Bergefurd.1@osu.edu or call the OSU South Centers 800-860-7232 or 740-289-2071, ext. 132.