Intercropping in maize silage versus solo-seeding for alfalfa establishment in Wisconsin and Idaho

Alfalfa (Medicago sativa L.) intercropping with maize (Zea mays L.) silage is being developed in the northern United States to improve the profitability and environmental sustainability of forage production. This study, conducted under rainfed conditions in Wisconsin and semiarid irrigated conditions in Idaho, compared the establishment of alfalfa and dry matter yield of four intercropping systems to three conventional systems. The former systems included alfalfa interseeded at planting or the vegetative emergence (VE) stage of maize and grown with or without prohexadione growth retardant. The latter systems included alfalfa seeded in spring, summer-seeded after barley (Hordeum vulgare L.), or late summer-seeded after maize silage. Spring seeded and interseeded alfalfa in Wisconsin also received foliar fungicide and insecticide during establishment. During alfalfa establishment, yield of intercropped maize silage was 1.8- to 4.4-fold greater than spring-seeded alfalfa. Compared to spring-seeded alfalfa, interseeded alfalfa had similar or somewhat lower stand density but similar first cut yield the following year, provided that intercropped maize was harvested near September 1 to allow ample alfalfa fall regrowth. Shifting interseeding from maize planting to the VE stage decreased early-season alfalfa growth, but improved maize silage yield, with minor effects on alfalfa fall growth, stand density, and first cut yield. Prohexadione application had little impact on establishment or yield of interseeded alfalfa. While having high plant density, alfalfa seeded after barley or especially maize had less fall growth and low first cut yield. Overall, alfalfa establishment and yield of intercropping systems compared favorably with conventional systems. Delaying alfalfa interseeding until the vegetative emergence stage improved maize silage companion crop yield. During alfalfa establishment, intercropped maize silage had up to 4.4-fold greater yield than solo-seeded alfalfa. Early harvest of maize silage improved fall growth and first cut yield of interseeded alfalfa after establishment. Interseeded and spring solo-seeded alfalfa had comparable stand density and first cut yield after establishment. Summer solo-seeded alfalfa had relatively poor fall growth and first cut yield after establishment.