Cover crops can provide ecological services and improve the resilience of annual cropping systems; however, cover crop use is low in corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotations in the upper Midwest due to challenges with establishment. Our objective was to compare three planting methods to establish cover crops (winter rye [Secale cereale L. ‘Rymin’], red clover [Trifolium pretense L. ‘Medium’], hairy vetch [Vicia villosa Roth], field pennycress [Thlaspi arvense L. ‘MN-106’], and a mixture of oat [Avena sativa L.], pea [Pisum sativum L.], and tillage radish [Raphanus sativus L.]) (MIX) in corn at the seven-leaf collar stage. Planting methods included directed broadcast into the inter-row (DBC), directed broadcast with light incorporation (DBC+INC), and a high-clearance drill (DRILL). The DRILL method achieved greater fall biomass than DBC for all species except pennycress, and DRILL and DBC+INC increased red clover and hairy vetch spring biomass compared with DBC. Cover crops did not affect corn grain or silage yield and reduced yield of the subsequent soybean crop by 0.4 Mg ha−1 (10%) only when poor termination of hairy vetch occurred at one site. Cover crops with >390 kg ha−1 of spring biomass reduced soil nitrate-N compared with the no-cover control. These results support that cover crops can be interseeded into corn at the seven-leaf collar stage in the upper Midwest to reduce soil nitrate-N while maintaining corn and subsequent soybean yields; however, effective cover crop termination is critical to avoid competition with the subsequent soybean crop.
Bibliographical noteFunding Information:
This work was supported by the Minnesota Department of Agriculture Clean Water Fund. We also appreciate the field support and technical contributions of Eric Ristau, Steve Quiring, Thomas Hoverstad, Wade Ihlenfeld, and all who assisted with planting, sampling, and analyses for this study.