Jarrod O. Miller, Assistant Professor and Extension Specialist, Agronomy, jarrod@udel.edu; Jamie Taraila, Graduate Research Assistant; Amy L. Shober, Professor and Extension Specialist, Nutrient Management and Environmental Quality, ashober@udel.edu
This fall marks the end of a three-year study sponsored by the Delaware NRCS to look at cover crop mixes and their effects on subsequent grain crops. On a sandy loam soil, we planted corn into bare plots, as well as plots containing rye, a rye/clover mix, and a rye/vetch mix. Cover crop biomass was burned down (terminated) either two weeks ahead or at planting.
We saw no effect of cover crop type on subsequent corn yields in 2019 and 2021 (Figure 1); however, corn yields in 2020 were higher in plots with cover crops than corn planted into the bare soil (Figure 1). We attribute the yield bump in 2020 to the protection that the cover crop biomass provided during early corn growth (V2/V3) during a late May freeze. Burning cover crops down two weeks prior to planting also significantly boosted corn yield (+15 and +10 bu/A in 2019 and 2020, respectively); there was no effect of cover crop termination timing on corn yields were similar in 2021 (Figure 2).
While planting a legume with rye did not significantly increase corn yield, it also did not result in yield decline. Overall, planting winter cover crops can help to improve soil health over the winter without limiting potential corn yields. However, planting green may cause corn yield losses depending on the year and field conditions.
Figure 1. Corn yields in 2019, 2020, and 2021 harvested from plots with different winter cover crops. Bars with the same letter were not statistically different.
Figure 2. Corn yields in 2019, 2020, harvested from plots with different cover crop termination timing (early or planting green). Bars with the same letter were not statistically different.