Impact of a Polymer on Calcium and Sulfur Availability in the Soil and Uptake in the Plant.

Gypsum provides soluble calcium and sulfate.  Calcium (Ca), besides being a nutrient also acts as a soil amendment to improve soil structure and remediate saline and sodic soils. Solubilized calcium does not remain free in the soil solution but is adsorbed by the soil exchange complex or reacts with carbonate forming an insoluble mineral.  Sulfur (S) is an essential plant nutrient that is vulnerable to losses by leaching or volatilization as hydrogen sulfide.  Blending an acidic polymer with gypsum enhances solubility and may provide more available Ca and S for a crop over the course of the growing season. Initial studies conducted in 2013 demonstrated that the polymer kept more calcium and sulfate available in the soil solution, even after 8 to 10 inches of rain over 65 days. Two large scale field projects were conducted, (1) with pelletized mined gypsum and (2) with by-product powdered gypsum from a lactic acid plant. The first project coated pelletized gypsum with a single rate of polymer before application. Treated and untreated gypsum was applied at 0, 280 and 560 kg/ha on an area planted to corn with 5 replications. The second project evaluated spraying 187 liters/ha of an aqueous polymer solution over by-product gypsum after application. Treated and untreated powdered gypsum was applied at 0, 1100 and 2200 kg/ha with two rates of polymer, 4.7 or 9.3 liters/ha. The area was planted to oats as a test crop.  Soil samples were collected before application and twice in-season to measure pH, extractable Ca, water soluble Ca and S, total Ca and S and sulfate. Plant samples were collected twice in season and total nutrient concentration were measured. Results show that polymer treatments resulted in more Ca and S available resulting in higher nutrient concentrations in plant tissues.