Corn density effect on interseeded cover crops, weeds, and grain yield

Abstract

A field experiment was conducted at three sites (New York, Pennsylvania, and Maryland) in 2016 to test the effects of drill interseeding a cover crop mixture consisting of cereal rye (Secale cereale L.), annual ryegrass (Lolium multiflorum Lam.), hairy vetch (Vicia villosa Roth), and red clover (Trifolium pratense L.) into organically managed corn (Zea mays L.). We quantified the effects of corn density on weed biomass, cover crop biomass, and corn grain yield. Increasing corn density had a direct negative effect on interseeded cover crop biomass as well as indirect effects that were mediated by light transmission and weeds. At two sites, corn grain yield at the low corn density (3.71 plants m–2) did not differ from corn grain yield at the standard density (7.41 plants m–2). We also compared plots with and without interseeded cover crops at the same standard corn planting density. Corn grain yield did not differ, but weed biomass at the October sample date was 31% lower in plots with interseeded cover crops compared to plots without. Our results suggest that organic farmers may be able to (i) improve weed suppression in corn by interseeding cover crops and (ii) optimize cropping system performance by planting corn at a slightly lower rate (e.g., 5–10%) than what is typically used when interseeding cover crops. Additional research should be conducted across a wider range of environments to determine corn planting rate recommendations that optimize corn yield, cover crop growth, weed suppression, and profitability in organic cropping systems.