Alfalfa Interseeded into Silage Corn Can Serve As a Cover Crop and Subsequent Forage Crop.

Alfalfa (Medicago sativa) and corn (Zea mays) silage are commonly grown in rotation in dairy forage production systems throughout the northern regions of the USA. Alfalfa interseeded with silage corn could potentially serve as a dual-purpose crop: as a cover crop during the silage corn production year, and then as a forage crop during subsequent growing seasons. A major obstacle to implementing this system has been that competition between the co-planted corn and alfalfa often leads to stand failure of the interseeded alfalfa. However, recent studies from Wisconsin demonstrated that foliar application of the plant growth regulator prohexadione-calcium to select alfalfa varieties can overcome this obstacle and successfully establish alfalfa interseeded with silage corn. In order to quantify the potential environmental and agronomic benefits of the corn-interseeded alfalfa system we compared this system with a conventional cropping system of silage corn followed by spring seeded alfalfa. Rainfall simulations performed at three stages in the growing season demonstrated that soil erosion in May, October, and the following spring was significantly reduced in the interseeding system. Additionally, total forage yield (corn silage + alfalfa) of the interseeded system exceeded that of the conventional system. While additional work is needed to refine the interseeded alfalfa system, the observed improvements in forage yields and soil conservation could provide powerful incentives for implementing this production system on farms in the northern USA.