By Hugo Ramirez Ramirez and Denise Schwab
Harvest at the Right Moisture Content
During the fermentation process, sugar in the chopped corn is converted into lactic acid by bacteria, but the silage needs to be at 35% dry matter to ensure it packs tight enough to become anaerobic so the bacteria can do their job. A ballpark indicator of whole plant moisture is the milk line on the kernel; harvesting at 2/3 to 3/4 milk line is a common practice to capture more energy as starch in the kernel. A better way to determine whole plant moisture is to actually chop up a few stalks and test it for moisture, either with a tester designed for this purpose or by using a microwave and kitchen scale. A general rule of thumb is that corn plants will dry about 0.5% points each day.
Chop Length and Kernel Processing
Good, timely fermentation requires an anaerobic environment where the bacteria have access to the sugars and starch in the chopped corn plant. Particle size (and moisture) has a big impact on packing density and oxygen exclusion. When a kernel processor is used, particle size should be about ¾,” and when a processor is not used the particles should be 1/4” to 1/2” in length.
Adding a lactic acid-producing bacteria (LAB) to the chopped corn increases the “good” bacteria and speeds the fermentation process, resulting in less spoilage and higher feed quality. Inoculants are simply inactive, live LAB which are activated when rehydrated, and because they are live bacteria, do not use chlorinated water to rehydrate the inoculant.
Packing to remove oxygen from the pile is critical since the bacteria require an anaerobic environment to ferment the forage. Density (pounds of forage per cubic foot) is used to measure the success of packing silage. Density is influenced by crop, chop length, dry matter, type of structure, delivery rate, packing weight, and time. The target density for a bunker silo is forty to forty-five pounds of fresh forage or fourteen-sixteen pounds of dry matter per cubic foot. Density also has an impact on spoilage during feedout, since a less-dense pile allows for more oxygen to enter the pile.
Sealing and Covering
Covering and sealing a silage pile may be the most important factor to ensure good fermentation and an anaerobic environment. A plastic cover specifically designed for use on silage piles that is at least 4-millimeters thick should be used. These special plastics are designed to resist tears and block ultraviolet light. Some plastics are even designed with high oxygen impermeability. Some plastic covers incorporate one layer of oxygen barrier film with a second layer of UV barrier, or producers can utilize an oxygen-limiting film next to the silage and a black/white UV plastic on top of it. Weight is needed on top of the plastic cover to hold the cover down and prevent air infiltration. Most producers use either old tires or tire sidewalls, and ideally the tires should touch each other, covering the entire pile.