Can Cover Crop Use Allow Increased Levels of Corn Residue Removal for Biofuel in Irrigated and Rainfed Systems?

Corn (Zea mays L.) residue removal at high rates can result in negative impacts to soil ecosystem services. The use of cover crops could be a potential strategy to ameliorate any adverse effects of residue removal while allowing greater removal levels. Hence, the objective of this study was to determine changes in water erosion potential, soil organic C (SOC) and total N concentration, and crop yields under early- and late-terminated cover crop (CC) combined with five levels of corn residue removal after 3 years on rainfed and irrigated no-till continuous corn in Nebraska. Treatments were no CC, early- and late-terminated winter rye (Secale cereale L.) CC, and 0, 25, 50, 75, and 100% corn residue removal rates. Complete residue removal reduced mean weight diameter (MWD) of water-stable aggregates (5 cm depth) by 29% compared to no removal at the rainfed site only, suggesting increased water erosion risk at rainfed sites. Late-terminated CC significantly increased MWD of water-stable aggregates by 27 to 37% at both sites compared to no CC, but early-terminated CC had no effect. The increased MWD with late-terminated CC suggests that CC when terminated late can offset residue removal-induced risks of water erosion. Residue removal and CC did not affect SOC and total soil N concentration. Particulate organic matter increased with late-terminated CC at the irrigated site compared to no CC. Complete residue removal increased irrigated grain yield by 9% in 1 year relative to no removal. Late-terminated CC had no effect on corn yield except in 1 year when yield was 8% lower relative to no CC due to low precipitation at corn establishment. Overall, late-terminated CC ameliorates residue removal-induced increases in water erosion potential and could allow greater levels of removal without reducing corn yields in most years, in the short term, under the conditions of this study.