Productivity, Economics, and Soil Quality in the Minnesota Variable-Input Cropping Systems Trial

Organic input (OI) and low external input (LEI) cropping systems with extended crop rotations have potential to maintain crop yields while enhancing net return and soil quality. From 1992 to 2007, contrasting cropping systems were evaluated in a 2-year soybean [Glycine max(L.) Merr.]-corn (Zea maysL.) rotation and a 4-year oat (Avena sativaL.)/alfalfa (Medicago sativaL.)-alfalfa-corn-soybean rotation in southwestern Minnesota. When compared to the high external input (HEI) 2-year rotation, corn grain yield was not reduced with LEI and OI 4-year rotations, and soybean yield was not reduced with the LEI 4-year rotation over all 16 years or with the LEI 2-year rotation in the last 4 years. Across years and crops, net return was 88% greater with the OI 4-year rotation than the HEI 2-year rotation, but was 19 and 15% lower with the LEI 2- and 4-year rotation, respectively. Particulate organic matter and potentially mineralizable C in 2001 were higher with the OI system than the other systems in both rotations. These results demonstrate that with diversified rotations, organic systems can produce high and profitable crop yields while enhancing soil quality, and that corn and soybean yields can be maintained in LEI systems. However, OI and LEI systems are constrained by greater management and labor requirements and pest management challenges than HEI systems.