Bunker Silo Cover Alternatives by Brian Holmes Extension Specialist, Biological Systems Engineering, UW-Madison Introduction Silage is covered for two primary reasons. First, covered silage reduces exposure to oxygen. Oxygen is required for the growth of aerobic organisms. These aerobic organisms cause the decomposition of valuable feed. A second reason for covering silage is to exclude rainfall.
Precipitation washes organic acids and other soluble feed components from the forage.
Organic acids keep silage pH low resulting in an environment that prevents growth of silage-decomposing organisms. In addition, precipitation introduces oxygen to the feed. Seepage caused by either high-moisture forage or precipitation carries away valuable feed nutrients and increases the risk of surface and groundwater contamination. Bunker silo covers should be selected based on their ability to exclude both air and precipitation. Plastic should be held in contact with the silage to keep air from moving under the plastic to get into the forage.