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

Authors: Gonzalez, Javier; DICK, WARREN - The Ohio State University; ISLAM, KHANDAKAR - The Ohio State University; Watts, Dexter; Fausey, Norman; Flanagan, Dennis; Vantoai, Tara; BATTE, MARVIN - The Ohio State University; REEDER, RANDALL - The Ohio State University; KOST, DAVID - The Ohio State University; SHEDEKAR, VINAYAK - The Ohio State University

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2022
Publication Date: 4/8/2022
Citation: Gonzalez, J.M., Dick, W., Islam, K.R., Watts, D.B., Fausey, N.R., Flanagan, D.C., VanToai, T.T., Batte, M.T., Reeder, R.C., Kost, D., Shedekar, V.S. 2022. Gypsum and cereal rye cover crops affect soil chemistry: Trace metals and plant nutrients. Soil Science Society of America Journal. 886:781-794. https://doi.org/10.1002/saj2.20394.
DOI: https://doi.org/10.1002/saj2.20394

Interpretive Summary: Food security is a pressing concern as the world’s population increases, while agricultural production remains the same or potentially decreases. Additionally, soil and water resources that food production relies upon need to be protected to avoid possible adverse effects on crop production. Thus, food production must increase while soil and water quality have to be maintained or improved. A multi-state, multi-year study was conducted to assess the effects of two conservation practices, i.e., surface application of synthetic gypsum and growing a cereal rye cover crop, on corn and soybean yields and soil and water quality. The study was conducted at four USA sites (two in Ohio, one in Indiana, and one in Alabama) where synthetic gypsum and cereal rye were implemented for five consecutive years under no-till. This paper reports the impacts of these conservation practices on soil chemistry relative to the control (no synthetic gypsum or rye cover crop), emphasizing heavy metals and plant nutrients that affect water quality. The results show that the synthetic gypsum used in this study did not contain heavy metals of environmental concern. In addition, the applications of synthetic gypsum and the implementation of cereal rye cover crops did not increase the levels of heavy metals in soils. The cover crop decreased phosphorus (P) levels in the soils, suggesting that the cereal rye residue retains P, which could reduce P transport from soils to water bodies, where it can decrease water quality. However, the remaining phosphorus in the cereal rye residue may not be available for crops. This research impacts scientists, natural resource agency personnel, extension agents, farmers, and others concerned with the use of synthetic gypsum and rye cover crops as conservation practices and how they can affect soil and water quality.

Technical Abstract: Worldwide 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 impact of two conservation practices, flue-gas desulfurization (FGD) gypsum (hereafter “gypsum”) soil amendment and cereal rye (Secale cereale) 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 five years 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)-soybean (Glycine max), and continuous soybeans]. Soils collected at 0-15 and 15-30 cm depths from each treatment at the end of the 5-year 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.