Corn silage harvest will have an extended season this year, reflecting the range of corn planting dates. Some of the late April planted corn will soon be ready for chopping. Producing a consistent, high quality corn silage requires planning and management. The goal is to provide an environment conducive to a quick and favorable anaerobic (without air) fermentation process. Characteristics of high quality silage include a pH below 4.5 and a lactic acid content of 65% or greater of the total volatile fatty acids. To accomplish this requires chopping at the correct moisture content, removing the air as quickly as possible after chopping, and maintaining an air/oxygen limiting environment throughout storage.
Pre-harvest planning is important to assure that harvest goes smoothly. Before the chopper pulls into the field make sure all the necessary equipment is ready to go. Know your harvest capacity in terms of tons of corn chopped per hour. Do you have the wagons/trucks/tractors to keep up with that capacity? Do you have the labor? Don’t forget about the need for packing tractors and drivers. If you use a custom harvester, meet with them well ahead of harvest. Outline your needs and expectations. Learn what you custom harvester can and can’t do and what time constraints they have. Think back to preceding years. What areas caused bottlenecks or created stress at harvest? Anything you can do now to anticipate potential disruptions and plan solutions will pay dividends at harvest.
The number one factor to manage silage quality is to harvest at the correct moisture or dry matter (DM) content. A DM range of 30-38% is acceptable. Silage put into a bunker silo should be at the lower end of this range while silage put into upright silos should be at the upper end. Strive for an average of 35% DM. Corn less than 27 to 30% DM does not ferment properly. It produces silage that often has high concentrations of butyric acid and will have an unpleasant odor resulting in reduced animal intake. Corn chopped at higher than 40% DM does not pack well, compromising the fermentation process. The result is a silage with low lactic acid concentration, heat damage and mold growth. Starch digestibility is usually low, causing the silage to have less energy. Rapid harvest is essential because corn will gain DM content or lose moisture on average at a rate of 0.5 percentage points per day.
Chop length and kernel processing affect the packing/air exclusion properties of silage and impact directly upon silage quality. The theoretical length of cut (TLC) for processed corn silage is ¾ inches. Non-processed corn silage should have a TLC of ¼ to ½ inches. If chop length is too coarse, packing is more difficult, and the result is poor fermentation. In recent years kernel processing has become a standard practice when chopping corn because it damages the protective layer of corn kernels, providing better access to the starch for rumen bacteria. Upon examination, correctly processed corn silage will not have any visible whole corn kernels or pieces of cob.
Most high quality silage producers use an inoculant. There are naturally occurring lactic acid bacteria (desirable) in the green chop coming out of the field. At issue however, are the other naturally occurring bacteria species that compete for the same plant sugars and that produce other acids. Adding an inoculant can help to speed up the fermentation process that drives lactic acid production. Regardless of which inoculant product is used, the key is to purchase high quality inoculants and to apply them correctly. Do not use chlorine treated water to rehydrate a bacterial inoculant.
The next critical step is the rapid removal of air by packing the green chop. This creates a favorable anaerobic environment for the lactic acid bacteria. The goal is to achieve a minimum silage density 40-45 lbs. of fresh forage/ ft3, which should provide a density of 15 lbs. of DM/ft3 or higher. Higher packing densities result in less DM loss. The guideline for packing is to provide 800 pounds of packing weight for each ton of silage delivered to the silo or pack. For example, if the harvest rate is 100 tons/hr. then the packing weight needed is 100 x 800 = 80,000 lbs. or 40 tons. Each packing layer should be no more than 6 inches in thickness. You cannot overdo packing.
Cover the silo or pile as soon as the final packing is completed. Covering prevents oxygen, weather and animals from getting into the silage pack, reducing DM and spoilage losses. The recommendation is to cover with plastic of 6 to 8 mil thickness provide adequate overlap and weigh that plastic down, sealing the edges as well. University research trials have demonstrated that the oxygen barrier 2-step products have reduced losses more than covering with the 6 to 8 mil plastic alone.
Finally, have a plan or system in place to manage and/or collect seepage from silage. This leachate cannot be allowed to enter any waterway, or public body of water.