Alfalfa Interseeded into Silage Corn Reduces Soil Erosion and Nutrient Losses and Enhances Productivity.

Alfalfa is an important forage crop that provides desirable nutritional, agronomic and environmental outcomes in dairy production systems. However, greater reliance on corn silage has reduced alfalfa acreage and may intensify negative environmental impacts of dairy forage production, such as nutrient pollution and soil loss. Interseeding alfalfa with corn silage could enhance first year alfalfa productivity while simultaneously mitigating soil and nutrient losses from corn silage-alfalfa cropping systems. Experiments were conducted in southern Wisconsin to compare the soil and water quality impacts of the interseeded alfalfa/corn silage system with a control system consisting of solo-seeded corn silage followed by spring seeded alfalfa. Three sets of rainfall simulation measurements were conducted at different stages of the interseeded system; results revealed that the interseeded system reduced soil erosion and runoff of nitrogen and phosphorus. Additional comparisons demonstrated significant decreases in soil inorganic N (NO₃^- + NH₄⁺) concentration in the interseeded system compared to the control system, indicating reduced risk of nitrate leaching. Other experiments in Wisconsin have established that successful interseeding of alfalfa with corn silage can increase productivity of first year alfalfa by two-fold. These significant improvements in soil and water conservation and productivity strongly incentivize further research into methods for optimizing the interseeding system.