AEROBIC DETERIORATION IN CORN-SILAGE RELATIVE TO THE SILO FACE

Movement of oxygen and subsequent microbial development and heating in corn silage were measured over four days at 5, 20, 35, and 50 cm from the exposed face in laboratory-scale (60 x 15.5 cm diameter) PVC silo s. In all six trials, most microbial activity occurred at the 5-cm lev el. Acetic acid bacteria initiated heating in all trials although yeas ts were significant in two trials. Bacilli were not important until si lage pH was above 5 and were associated with a secondary temperature r ise in four trials. Oxygen entering the silage at the open face was ut ilized principally near the face, and temperatures above 40-degrees-C were observed only at the 5-cm level. Heating at 20 cm occurred in all trials, but appeared to result from heat transfer from the active zon e rather than from microbial activity at that depth. A diffusion-based , one-dimensional model of aerobic deterioration in silage reasonably predicted oxygen, temperature, and microbial numbers although the pred icted progression of deterioration relative to the exposed face was co nsistently too fast. Model predictions were improved by reducing the c alculated porosity for diffusion by 30%.