Impacts of Spring-interseeded Cover Crops on Late-emerging Weed Suppression and Ground Cover in Corn (Zea mays L.) Production Systems

Any alternative crop management strategy will only be adopted by growers if yield is not negatively impacted, fits within a current management practice, is easily implementable with minimal cost, or provides other beneficial features such as weed control or suppression. Corn production that incorporates a cover crop as an alternative weed control strategy and ground cover may support a sustainable system that is less dependent on herbicidal weed control. In addition, the cover crop may be used as a fall forage, act as a slow release fertilizer source the following year, and provide ground cover to reduce soil erosion. In South Dakota, cover crop establishment cannot occur after corn harvest, as the growing season is too short, cold, and often dry. Therefore, interseeding cover crops into standing corn has the potential to establish, suppress late-emerging weeds, and provide late season ground cover. The purpose of this research was to examine if a cover crop mixture could be established in a standing corn crop at V5 growth stage, suppress weeds, and provide ground cover after corn harvest without negatively impacting corn yield. Crimson clover (Trifolium incarnatum), winter wheat (Triticum aestivum) and lentil (Lens culinaris) were planted using broadcast or drill methods, as a mixture at a rate of 5.4, 8.9, and 9.8 kg ha-1, respectively, into V5 corn in field studies from 2010 – 2012. In 2010 - 12, the mix was planted at summit (SMT) and toeslope (TSP) locations in corn fields near Andover, SD. In 2011 – 12 the mix also was planted at SMT and TSP locations near Trail City, and in a flat field near Aurora, SD. Corn and cover crop and weed biomass were collected each fall. Cover crops emerged about 14 d (days) after planting. Winter wheat and crimson clover were the only species that survived until corn harvest. The drill interseeding method had 76% more cover crop biomass than the broadcast method. Cover crops drill seeded reduced grass weed biomass by 38%. Regardless of seeding method, cover crops had no impact on corn grain yield. These results indicate that cover crops could be established in standing corn with no adverse yield impact. These crops provided ground cover during and after the corn growing season and suppressed late-emerging grass weed growth. Therefore, interseeding this cover crop mix into standing corn may be a feasible alternative management strategy for getting a cover crop established, as SD weather is too cold, dry, and season too short for after harvest planting