Redistribution of Nitrogen in Urea-Treated and Soybean Meal—Treated Corn Silage

Abstract

The redistribution of nitrogen when urea in three proportions (0.5, 0.75, and 1.0%) or equivalent amounts of nitrogen from soybean meal were added to whole corn plants at ensiling was studied with 294 plastic bag silos. The corn was harvested at three stages of maturity: Low dry matter (25.6%), medium dry matter (30.4%), and high dry matter (52.0%). Only the lowest level of urea and soybean meal was added to the high dry matter samples. Triplicate silages were prepared and analyzed for the various nitrogen fractions after 0, 0.5, 1, 3, 7, 21, and 42 days of storage.Dry matter decreased (P<.01) with storage time. Nonprotein nitrogen increased (P<.01) and protein nitrogen decreased (P<.01) in all silages with storage time. Only 25% of the urea nitrogen was recovered in the low and high dry matter silages, whereas 50% was recovered from the medium dry matter silage treated with 0.5% urea. Averaged over all levels of nitrogen supplementation, ammonia nitrogen was 19, 18, and 15% of the total nitrogen in urea-treated low, medium, and high dry matter corn silages and 6, 4, and 4% in similar soybean meal-treated samples after 42 days of storage. Nitrate reduction was greater in the soybean meal (70%) than in the urea-treated silages (55%).