Interseeding Cover Crops in Corn in Michigan.

Time constraints limit the opportunity to seed cover crops in the fall in the upper Midwest following corn harvest. Interseeding cover crops into corn during the early vegetative growth stage may increase cover crop biomass and soil health benefits. However, cover crops may be competitive with corn if seeded too early. We evaluated the establishment and competitiveness of annual ryegrass, crimson clover, and Tillage Radish® interseeded into corn in 2015, 2016, and 2017 at the V1, V2, V3, V4, V5, V6, and V7 growth stages at East Lansing, MI. The experiment was replicated in Richville, MI in 2017. Seeding rates were 16.8 kg/ha, 16.8 kg/ha, and 9.0 kg/ha for annual ryegrass, crimson clover, and Tillage Radish®, respectively. Weed free and no cover control plots were also included. Cover crop and weed density were measured 30 days after each seeding time; cover crop and weed density and biomass were measured in October prior to corn harvest, and again the following spring in April. In 2015, weed density was greatest at the V1 interseeding timing, resulting in corn grain yield reduction. Cover crop density and biomass were greatest for the V4-V6 interseeding timings; annual ryegrass had the highest density and biomass, and crimson clover the least. In 2016, dry conditions at all interseeding timings reduced cover crop and weed density and biomass compared with 2015. There were no differences in corn grain yield in 2016. In 2017, all cover crops emerged at both locations when seeded prior to V7; crimson clover and Tillage Radish® did not emerge at Richville when seeded at V7. Common lambsquarters emergence was greater in the early interseedings at Richville; winter annual weed emergence was greater in East Lansing in the later interseedings. Annual ryegrass, crimson clover, and Tillage Radish® established from V2-V7 in corn and did not reduce corn grain yield; however, continued research on cover crop seeding rates and weed control options for early interseeded cover crops is needed.