Gypsum and Carbon Amendments Influence Leachate Quality from Two Soils in Ohio, USA

Interest and awareness by farmers and land managers of the potential impacts of gypsum and crop residues to improve soil quality is increasing. However, how these amendments affect water quality of two contrasting soil types in Ohio is not well understood. A greenhouse experiment was conducted to study the leachate quality in response to addition of crop residues (0 and 13.4 Mg ha–¹), glucose (0 and 4.5 Mg ha–¹), and gypsum (0, 8.9, and 26.9 Mg ha–¹) to Wooster silt loam (mixed, mesic Typic Fragiudalfs) and Hoytville clay loam (fine, illitic, mesic Mollic Epiaqualfs) soils. Constant head of water was used to generate leachate for 25 min and samples were analyzed for pH, nutrients, and heavy metals. In Hoytville soil, gypsum significantly increased Ca, Mg, S, and Na concentrations in leachates and decreased P and Fe. However, no significant differences were observed between gypsum low and high rates on P reductions in leachate water. In Wooster soil, gypsum reduced K and increased Ca and S concentrations. Residues and glucose increased P concentration significantly in leachates collected from both soils. Glucose addition increased Ca and Mg concentrations in leachates from the less pH buffered Wooster soil, but these elements were decreased for the Hoytville soil. Concentration of trace elements in leachates were found to be below maximum contaminant limits as prescribed by USEPA in drinking water standards. The lower rate of gypsum (8.9 Mg ha–¹) application is sufficient to reduce P loads in leachate water and reduces cost compared with higher application rates.