Short-term responses of soils and crops to gypsum application on organic farms

Gypsum is a high calcium (Ca) and sulfur (S) containing mineral used to improve soil fertility and physical characteristics in organic cropping systems. However, evidence regarding short-term improvements in soil properties and increased crop yield is lacking. We conducted replicated experiments on 14 different organic dairy farm fields in five Ohio counties in 2017 and 2018. Our analysis evaluated short-term effects of gypsum application on (a) nutrient concentrations in soils and crop tissues, (b) yield of corn (Zea mays L.) and forage (alfalfa [Medicago sativa L.] or alfalfa-mixed grasses], and (c) and soil health properties. There were no effects on the yield of corn and forage after one or two annual gypsum applications. Still, gypsum consistently increased S concentrations (P < .1) in soil and crop tissues as soon as 5 mo after each application. Gypsum had no measured effects on soil mineralizable carbon (C), penetrometer resistance, or unsaturated hydraulic conductivity in the short term. Soil protein, permanganate oxidizable C, and Mehlich-3 magnesium levels were lower after the second application (P < .1). Our results indicate a short-term effect on some soil and crop nutrients but no additional benefits to soil health or crop yield in the short term when gypsum was applied to organically managed soils.