ALFALFA AND CORN-SILAGE SYSTEMS COMPARED ON MICHIGAN DAIRY FARMS

Two primary roughages used for diets of dairy cows are corn silage (Ze a mays L.) and alfalfa (Medicago sativa L.). A dairy forage system mod el was used to compare the relative merits of these two forages when v aried amounts (none, one-third, two-thirds, and all on a dry matter ba sis) of the forage requirement were ammoniated corn silage and the rem ainder 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 representati ve farms using a partial budget analysis synthesized from research rep orts and surveys. The highest net return was from alfalfa at 100% of t he forage requirement, but differences in net returns across forage sy stems were small compared with the variation caused by weather among y ears. Changes in assumptions concerning farm size, soil type, crop yie ld, milk production, relative prices, and manure handling did not affe ct the conclusions of the analysis. In systems that used all alfalfa f orage, much of the manure was applied to alfalfa crops, a practice tha t is normally discouraged because the manure reduces weed control, sta nd persistence, and yield. With alfalfa at 100% of the forage requirem ent, 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 prac tice of having at least one-third of the forage requirement provided b y each of the forage crops is favored to improve management of crops, manure disposal, and labor.