Gypsum, crop rotation, and cover crop impacts on soil organic carbon and biological dynamics in rainfed transitional no-till corn-soybean systems

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

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2022
Publication Date: 9/27/2022
Citation: Islam, K.R., Dick, W.A., Watts, D.B., Gonzalez, J.M., Fausey, N.R., Flanagan, D.C., Reeder, R.C., Vantoai, T.T., Batte, M.T. 2022. Gypsum, crop rotation, and cover crop impacts on soil organic carbon and biological dynamics in rainfed transitional no-till corn-soybean systems. PLOS ONE. 17(9). Article e0275198. https://doi.org/10.1371/journal.pone.0275198.
DOI: https://doi.org/10.1371/journal.pone.0275198

Interpretive Summary: Soil organic carbon is an indicator of soil quality, influenced by management practices. We investigated the effect of management practices on soil organic carbon quantity and quality under no-till rainfed field experiments at four different sites in the USA. The treatments were annually applied gypsum (0, 1000, and 2000 lbs/acre), cover crop cereal rye implementation (or not) to continuous soybeans or corn-soybean rotation. After the 5-year study, soil samples were collected and analyzed for soil organic carbon, total nitrogen, the mass of soil microbes, labile carbon (readily available food and energy source for soil microbes), and soil organic carbon management indices. The results indicated that gypsum, cover crops, and crop rotation affected soil organic carbon quantity and quality within and across the sites. Gypsum applied annually at 2000 lbs/acre increased the mass of soil microbes within individual sites and by 41% when averaged across all sites compared to the control. Also, across all sites, gypsum increased labile carbon. The corn-soybean rotation compared to continuous soybeans increased soil organic carbon and labile carbon and soil organic carbon management indices but decreased the mass of soil microbes within and across the sites. The above results suggest that increasing soil organic carbon significantly decreased its lability. Measuring these variables can indicate management-induced changes in soil organic carbon storage or depletion and soil organic carbon lability.

Technical Abstract: Soil organic carbon (SOC), a composite indicator of soil quality, is influenced by management practices. The objective of our study was to elucidate the impact (2012- 2016) of gypsum, crop rotation, and cover crop on SOC pools and on several soil biological variables. No-till rainfed field experiments at four different sites in the United States were conducted using a three-factorial randomized complete block design with gypsum (broadcasted at 0, 1.1, and 2.2 Mg/ha annually), a plus or minus cereal rye (Secale cereal) cover crop, and crop rotation [continuous soybean (Glycine max, SS) or corn (Zea mays)-soybean CS phases] in a two-year rotation. Soil samples were analyzed for microbial biomass C SMBC), SOC, total N (TN), active C (AC), cold (CWC) and hot (HWC) salt-water extractable C, SMBC: SOC as qR, C pool index (CPI), C lability index (CLI), and SOC management indices (CMIs). Results showed variable main effects of gypsum, crop rotation, and cover crop on SOC pools, TN, and SOC lability within and across the sites without any consistent interactions. Gypsum applied at the 2.2 Mg/ha rate increased the SMBC within individual sites and by 41% when averaged across all sites compared to the control. Likewise, the qR, AC, and HWC, indicators of the labile SOC pool, were increased by gypsum when averaged across all sites. The CS rotation compared to SS increased SOC, AC, CPI, and CMIs but decreased SMBC and qR within and across the sites. Our results suggest that the sensitive dependent variables that responded to the combined treatments of gypsum (2.2 Mg/ha), crop rotation (CS), and cover crop (rye) were SMBC, qR, AC, and CMISMBC. Increasing SOC (accumulation) significantly decreased its lability. Measuring these variables can provide an early indication of management-induced changes in SOC storage or depletion and on SOC lability.