Crop Rotation and Tillage Management Effects on Grain Yield in Southeastern South Dakota, 1991-2016.

Diversified crop rotation and soil health are prime factors in creating a productive growing environment for South Dakota crops. Viewing this as vital to sustainable and profitable crop production for our state, long-term plots were established in 1991 at the Southeast Research Farm near Beresford, SD to evaluate long-term effects of no-till versus conventional till production under three different crop rotations. Rotations consisted of ‘2-year’ (corn/soybean), ‘3-year’ (corn/soybean/wheat or oat), and a ‘Flex’ rotation where different crops were planted as needed including corn, soybean, small grain, and alfalfa. Within a given rotation, each crop was present within a no-till and conventional till plot area in each year of the study. The trial was set up in a split plot design with rotation being the main plot and tillage the split plot. Comparing over 26 seasons and across rotations, soybeans yielded significantly higher in no-till plots than in tilled plots. Within individual rotations, the 2-year and Flex rotations showed significantly higher soybean yields with no-till management, and the 3-year rotation showed a trend for higher yields with no-till. On average, corn did not show any significant yield differences between tillage treatments, but tended to be 5 to 7 bu/ac lower under no-till within the 2-year rotation. This trend was not observed in the 3 year and Flex rotations where there was more crop diversity. In summary, soybean yields tended to be higher with no-till, while no-till corn showed a trend for slightly lower yield when grown in a short rotation.