Alfalfa and Corn Silage Systems Compared on Michigan Dairy Farms

Two primary roughages used for diets of dairy cows are corn silage (Zea mays L.) and alfalfa (Medicago sativa L.). A dairy forage system model was used to compare the relative merits of these two forages when varied amounts (none, one-third, two-thirds, and all on a dry matter basis) of the forage requirement were ammoniated corn silage and the remainder was alfalfa. Primary comparisons were the net return above feed and manure costs, but manure management issues and labor requirements were also considered. Economic comparisons were made for representative farms using a partial budget analysis synthesized from research reports and surveys. The highest net return was from alfalfa at 100% of the forage requirement, but differences in net returns across forage systems were small compared with the variation caused by weather among years. Changes in assumptions concerning farm size, soil type, crop yield, milk production, relative prices, and manure handling did not affect the conclusions of the analysis. In systems that used all alfalfa forage, much of the manure was applied to alfalfa crops, a practice that is normally discouraged because the manure reduces weed control, stand persistence, and yield. With alfalfa at 100% of the forage requirement, large amounts of excess manure nitrogen were produced on the farm. Application of nitrogen to alfalfa must be compensated by a reduced nitrogen fixation to avoid ground water contamination. Because of the lack of a strong economic advantage among the forage systems, the practice of having at least one-third of the forage requirement provided by each of the forage crops is favored to improve management of crops, manure disposal, and labor.