Optimization of Cover Crop Establishment Technologies in Corn-Based Cropping System.

Cover cropping can reduce agricultural runoff and N loss, but has not been widely adopted in the upper Midwest due to climatic challenges in establishment and a lack of reliable management practices. A study was initiated in 2014 to investigate the suitability of five cover crop options (cereal rye (Secale cereale), red clover (Trifolium pratense), hairy vetch (Vicia villosa), field pennycress (Thlaspi arvense), and a mixture of oat (Avena sativa), pea (Pisum sativum), and tillage radish (Raphanus sativus)) planted into V7 corn via three interseeding methods (a multi-purpose cover crop InterSeeder^TM, directed broadcast, and directed broadcast with light incorporation) at the University of Minnesota Southern (Waseca, MN) and Southwestern (Lamberton, MN) Research and Outreach Centers. All cover crops established and survived through the fall except for the mixture, which senesced under the corn canopy at both locations. There were no significant differences (α = 0.05) in corn yield at either location. In Lamberton, cover crop option affected tissue N (P < 0.007) and dry matter (P < 0.001), but performance was not affected by planting method. Only rye (540 kg DM ha^-1; 15 kg N ha^-1) and pennycress (259 kg DM ha^-1; 10 kg N ha^-1) overwintered at the Lamberton location. In Waseca, all winter-hardy cover crop options survived the winter. Cover crop option and planting method impacted both spring dry matter and tissue N content (P < 0.05). Across planting methods and cover crop options, dry matter values ranged from 233 (broadcast pennycress) to 1103 kg ha^-1 (broadcast rye), and tissue N (kg ha^-1) ranged from 12 (broadcast + incorporation pennycress) to 44 kg N ha^-1 (InterSeeder^TM planted hairy vetch). Broadcast with incorporation achieved dry matter and tissue N values equivalent to corresponding InterSeeder^TM treatments, and significantly greater than broadcast without incorporation in hairy vetch (P < 0.001) and red clover (P = 0.05), highlighting the benefit of soil disturbance and improved seed-soil contact. At cover crop termination in Lamberton, soil NO₃-N was significantly lower (P < 0.001) in InterSeeder^TM rye treatments (4.18 kg NO₃-N ha^-1) than all other InterSeeder^TM planted cover crops and the no-cover check (17.61 kg NO₃-N ha^-1) at depth 1 (0-30 cm) and 2 (30-60 cm) (P < 0.001). In Waseca, all established cover crops resulted in less soil NO₃-N ha^-1 than the mixture and the no-cover control at depths 1 and 2 (P < 0.001). Broadcast with incorporation or a cover crop InterSeeder^TM can be used to effectively establish cover crops in standing corn, reducing N loss while maintaining corn yield.