Effect of Nitrogen Source, Stage of Maturity, and Fermentation Time on pH and Organic Acid Production in Corn Silage

Abstract

Two hundred and ninety-four plastic bag silos were prepared to determine the effect of adding urea or soybean meal on the corn plant fermentation process. Urea was added at 0.5, 0.75, and 1.0% of fresh silage weight at ensiling. Equivalent amounts of nitrogen from soybean meal were added for a comparative treatment. The corn was harvested at three stages of maturity, 25.6, 30.4, and 52.0% dry matter. Only the lowest level of urea and soybean meal was added to the silage containing 52.0% dry matter. Triplicate silages were prepared and analyzed after 0, 0.5, 1, 3, 7, 21, and 42 days of storage.Over all treatments the average pH of urea-treated corn silage (4.85) was higher than that of soybean meal-treated corn silage (4.69). Differences between treatments after 42 days of fermentation were greater with either low or high dry matter silages than with medium dry matter. Total organic acid concentration declined from 11.94% of dry matter in low dry matter samples after 42 days of storage to 3.14% of dry matter in high dry matter samples averaged over all treatments. The concentration of these acids increased (P<.01) with storage time and was higher in the urea-treated samples. Contrary to what was observed with lactic acid, volatile fatty acids were higher with the lower nitrogen supplementation. Acetic acid comprised 90% of the total volatile fatty acids.