Optimizing Management for Establishment of Alfalfa Interseeded into Silage Corn.

Interseeding alfalfa at corn planting could serve as a cover crop to reduce soil and nutrient losses during corn silage production, and has potential to enhance productivity by bringing alfalfa into full forage production the following year. In Wisconsin, interseeded corn silage and alfalfa reduced runoff of nitrogen and phosphorus by 23-82% and soil erosion by 45-87% compared to conventional corn silage. Additionally, compared to conventionally spring-seeded alfalfa the interseeded system doubled the average first year yield. Preliminary economic analyses demonstrated the overall net returns of a five-year rotation is increased by about 30% ($64 ha^-1 yr^-1) with interseeding. However, frequent alfalfa stand failure during interseeding is a challenge that requires innovative solutions. Multiple Wisconsin studies have demonstrated that properly timed applications of the plant growth retardant prohexadione-Ca (PHD) to alfalfa seedlings frequently doubles stand density of alfalfa established in corn. Selection of suitable alfalfa varieties is important for successful alfalfa establishment in corn, as a comparison of varieties demonstrated that substantial differences in both plant survival and response to PHD when interseeded into corn. Overall, these results suggest the corn-interseeded alfalfa production system could be reliably implemented if an appropriate alfalfa variety is sown and treated with PHD. The extensive economic and environmental benefits of the system provide powerful incentives for continuing development of interseeded alfalfa/corn silage systems for use in cold temperate regions.