Gypsum and cereal rye cover crops affect soil chemistry: Trace metals and plant nutrients

Abstract

AbstractWorldwide food security is a pressing concern as population increases. Thus, there is a need to increase food production on existing farmland while improving soil health and water quality. We report the effect of two conservation practices, flue‐gas desulfurization (FGD) gypsum (hereafter “gypsum”) soil amendment and cereal rye (Secale cereale L.) cover crop, on soil chemistry. Emphasis was placed on extractability of trace metals (Cd, Cr, Cu, Ni, and Zn) and plant nutrients (Ca, K, Mg, Mn, Mo, P, and S). Research was conducted under no‐till management for 5 yr at four sites. Treatments consisted of annual gypsum soil surface application (0, 1.1, and 2.2 Mg ha–1), with and without cover crops, and two crop rotations [corn (Zea mays L.)–soybean [Glycine max (L.) Merr.], and continuous soybean]. Soils collected at 0‐to‐15‐ and 15‐to‐30‐cm depths from each treatment at the end of the 5‐yr study were microwave‐digested with 3:1 HNO3/HCl and analyzed for trace metals and nutrients. Gypsum chemical analysis indicated it did not provide trace metals that impair soil/water quality. However, it did provide Ca, S, and other nutrients supporting plant growth. Furthermore, gypsum and cereal rye winter cover crop, relative to the control and under the conditions of this study, did not increase extractability of most trace metals from soils. The cover crop, relative to the control, also significantly decreased P extractability, suggesting cereal rye immobilizes P, potentially decreasing off‐site transport to water bodies. Under the conditions of this study, gypsum and winter cover cereal rye did not increase extractable trace metals.