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

Abstract

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 mays L.) rotation and a 4year oat (Avena sativa L.)/alfalfa (Medicago sativa L.)-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 2year rotation, but was 19 and 15% lower with the LEI 2and 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. Introduction Long-term agronomic studies integrate environmental and cropping effects to provide a realistic picture of the impact of production practices on crop yield and yield stability, net return, economic risk, pest populations, and soil properties. Long-term research is especially important when evaluating rotations of several crops which may be grown only once within a 4to 5-year cycle. The Morrow Plots, established in 1876 in Illinois, are the oldest example of cropping systems research in the United States (34). This experiment has shown the value of crop rotations with a forage legume in maintaining longterm corn yield compared to continuous corn. The Morrow Plots were also among the first to show the value of manure and fertilizer inputs for sustaining crop yields and soil organic C (2,34). More recently, long-term experiments in the Midwest have re-confirmed the value of forage legumes in crop rotations and have demonstrated the economic and agronomic potential of OI and LEI systems in rotations (7,8,10,13,17,37). However, with the availability of inexpensive fertilizers and pesticides and the decline of livestock on farms beginning in the mid-1900s, many farmers in the Midwest made the transition from diversified cropping systems containing forages to more specialized grain cropping systems (19). Risks associated with these simpler cropping systems were supported by strong commodity markets for grain, federal price supports, and crop insurance programs. 29 April 2013 Crop Management Published June 13, 2014