Cropping systems with less reliance on external inputs could improve agricultural sustainability if they can produce high and stable crop yields over time. A 16-yr experiment was conducted in southwestern Minnesota to evaluate the effects of zero external input (ZEI), low external input (LEI), high external input (HEI), and organic input (OI) systems on crop yield and yield stability in a 2-yr soybean [Glycine max (L.) Merr.]-corn (Zea mays L.) rotation and a 4-yr oat (Avena sativa L.)/alfalfa (Medicago sativa L.)-alfalfa-corn-soybean rotation. Oat yield was stable and highest with the LEI, HEI, and OI systems. Alfalfa yield was highest with the LEI, HEI, and OI systems in the fi rst 8 yr and the OI system in the last 8 yr. Corn grain yield was 0, 13, 26, and 40% greater with the 4-yr rotation than the 2-yr rotation in the HEI, LEI, OI, and ZEI systems, respectively, and was greatest with the HEI system in the 2-yr rotation and the LEI, HEI, and OI systems in the 4-yr rotation. Soybean yield was 7% greater with the 4-yr rotation than the 2-yr rotation and was among the highest with the LEI and HEI systems. Stable corn and soybean yields occurred with the LEI and OI systems, while above-average yield increases under favorable growing conditions occurred with the LEI and HEI systems in alfalfa and the HEI system in corn. These results demonstrate the value of extended crop rotations for corn and soybean, and that high crop yields can be obtained with reduced-input systems.
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