Legume Cover Crops and Tillage Impact Nitrogen Dynamics in Organic Corn Production

Core Ideas Reduced tillage of legume cover crops releases significant amount of N coupled with corn N uptake. Roller crimper termination of legumes releases nitrogen at similar total amounts to disking. Increased experimentation needed to improve corn population and yields in roller crimped stands. Cover cropping and reduced tillage are two management practices that increase ecosystem services in agroecosystems. However, their interactive effects on N dynamics and cash crop yield are underexplored. In this study, four different termination approaches, employing no‐till and tillage, and organic and conventional techniques were used with four winter annual leguminous cover crop species to investigate the combined effect on plant‐available nitrogen (PAN) and subsequent organic corn (Zea mays L.) yield. Termination treatments included roller‐crimping, flail‐mowing, disking, and herbicide application with cover crops of Austrian winter pea (Pisum sativum L. subs. arvense, AWP), hairy vetch (Vicia villosa var. AU Early Cover, HV), balansa clover [Trifolium michelianum Savi ssp. balansae (Boiss.) Ponert, BC] and crimson clover (Trifolium incarnatum var. Dixie, CC). Plant‐available N (NO3− and NH4+) was determined using biweekly soil inorganic N extractions and resin probes. Cover crop biomass, cover crop C/N ratio, and cover crop total N were measured prior to termination. Nitrogen was most available from AWP and HV across termination methods at 6 to 10 wk after termination. Disked HV contributed highest levels of N across all 16 cropping by termination combinations. Highest biomass N was found in HV (226 kg ha−1), followed by AWP (189 kg ha−1) and CC (181 kg ha−1). Corn yield ranged widely, from 0.23 Mg ha−1 in 0 N control to >9 Mg ha−1 in HV and AWP treatments. Cover crop species plays an important role in N dynamics, frequently influencing soil processes to a more significant degree than termination approach.