Research results in Indiana show gypsum reduces soluble reactive phosphorus on agricultural lands

Poor soil conditions in Midwest agricultural lands can reduce plant uptake of nutrients leading to over-application of fertilizers and pesticides. Excess nutrients run off fields into waterways where they contribute to toxic algal blooms that threaten public health, as well as eutrophication that harms aquatic life. One best practice that improves soil conditions is the use of calcium sulfate (gypsum) as a soil amendment; it improves nutrient uptake by the plants and reduces loss from the fields into the waterways.

Dr. Pierre Jacinthe of Indiana University-Purdue University Indianapolis (IUPUI) just completed the first year of gypsum research in the Walnut Creek Watershed in Indiana. Indianapolis Power & Light and GYPSOIL sponsored this project that Greenleaf originated and oversaw. Ron Chamberlain of GYPSOIL provided agronomic consultancy. Dr. Jacinthe’s team selected two fields near North Salem, IN and managed them with identical crop rotation, fertilizer application, and other farm practices. The researchers collected and analyzed soil and water samples.

The results: gypsum application reduced soluble reactive phosphorus (SRP) concentrations by an average of 41% during the growing season. SRP is the limiting factor in many regional waterbodies; this means that it is the primary contributing factor to problematic algal blooms.   In the study, gypsum application also increased electrical conductivity, microbial biomass carbon, and soil respiration. Microbial biomass carbon and soil respiration are related to soil health.

The Indiana study complements a research project underway in Ohio, where Greenleaf assists Dr. Warren Dick of The Ohio State University in the Maumee River Basin.  This three-year study has reduced soluble reactive phosphorus concentrations in tile water runoff at the gypsum-treated fields by an average of 54% compared to the untreated fields. The phosphorus reductions in tile drainage water persisted at least 20 months after gypsum treatment.

Read more about this research into the use of gypsum as a best management practice here.

View our other work with partners in soil and water health.