Short-Term Stover, Tillage, and Nitrogen Management Affect Near-Surface Soil Organic Matter

Corn (Zea mays L.) stover removal for biofuel or forage has implications on soil organic C (SOC). The objective of this study was to evaluate short-term (3-yr) stover management (retained or removed [79% removed, across treatments and years]), tillage system (chisel tillage, strip-tillage, and no-till [CT, ST, and NT, respectively]), and fertilizer N (0 and 224 kg N ha-1) effects on particulate and total soil C and N in continuous corn (CC) cropping systems on fine-textured soils in the Upper Midwest. Soil samples were collected at study initiation in 2008 and at its conclusion in 2011. Stover removal decreased SOC in the surface depth (D1) by 15% compared to when it was retained and 11% when compared with the baseline level. In the same depth, SOC with CT was 10 and 9% less than with ST and NT, respectively, and 10% less than the baseline. Particulate organic matter C (POM-C) decreased in D1 between sampling times with stover removal in all tillage systems. When stover was retained, POM-C in D1 increased 36 and 40% over the baseline with ST and NT, respectively, but decreased 18% with CT. Chisel tillage decreased POM-C in the sampled soil profile by 13 and 17% compared with ST and NT, respectively, and by 21% when compared with the baseline. These results demonstrate that annually harvesting the maximum quantities of stover in CC allowable by field-scale machinery can reduce near-surface particulate and total soil organic matter in the Upper Midwest after 3 yr, but losses can be reduced by tillage systems that reduce soil disturbance.