Harvesting corn for silage can provide a high-yielding and highly-digestible source of animal feed for livestock producers. Harvesting silage can also help to extend the harvest window for corn across an operation and can be used to salvage problem or stressed fields. While corn silage can be a cost-effective forage source, management is needed to ensure that silage quality and feed value is maintained.
If selecting fields for silage during the planting season, management choices that can affect silage quality include product selection, planting population, planting date, and fertility. To have the most impact on silage yield and quality, recommendations include selecting products that are 10 days longer than a full-season product used for grain, planting at higher seeding rates, and increasing fertility levels. When selecting fields for silage in-season, stressed fields with limited grain production may be a better option for silage tonnage than grain use but must be managed due to the potential stress issues that could occur. Because drought stressed corn can have increased nitrate levels in the lower third of the stalk, the stalks should be chopped at a height around 12 to 16 inches to help reduce the potential of nitrate toxicity.1
The number one priority for harvesting silage is to harvest corn at the proper moisture content. Corn harvested for silage should be near 65% moisture (35% dry matter) for an up-right silo and 70% moisture for bunk or bag silage to help ensure that silage packs tight enough to allow for an oxygen free environment to allow the bacteria to ferment the silage. While a general rule of thumb is to begin harvest once grain reaches the ⅔ to ¾ milk line (Figure 1), plants can also be chopped to determine plant moisture content. When chopping silage, particle size can have a dramatic impact on fermentation. If using a processor, particle size should be ¾ inches, with a length of ¼ to ½ if not using a processor.
Bacteria breaks down the sugars in the silage into lactic acid anaerobically (without oxygen), and silage that is packed tightly helps exclude oxygen. While bacteria may occur naturally, adding a lactic acid-producing bacterium to chopped silage can speed up the fermentation process and increase feed quality. Inoculants, which are inactive bacteria that need to be rehydrated, should not be rehydrated with chlorinated water.
Once harvested, packing the silage to ensure anaerobic conditions necessary for formation is critical. The density of the forage, which is determined by chop length, moisture content, dry matter, structure type, delivery rate, and packing weight, influences packing success. A good target density to aim for is 45 pounds of fresh forage (15 pounds of dry matter) per cubic foot.
After the silage is packed, the silage pile needs to be sealed and covered. Proper sealing and covering of a silage pile may be the single most influential factor affecting silage quality. Use a plastic cover specifically designed to cover silage that is at least 4 mil thick. Weight should be added to the top of the cover to hold it down to help prevent air from infiltrating into the pile.
1McFadden, M., Bucholtz, H., and Allen, M. Updated 2007. Harvesting drought stressed corn for silage. Michigan State University. https://www.canr.msu.edu/.
Roth, G.W. and Heinrichs, A.J. 2001. Corn silage production and Management. Agronomy Facts 18. Penn State Extension. https://extension.psu.edu/.
Ramirez, H.R. and Schwab, D. 2019. Corn silage tips. Iowa State University Extension and Outreach. Iowa State University. https://www.extension.iastate.edu/.
Schwab, D. 2018. Silage making with 2018 weather challenges. Iowa State University Extension and Outreach. Iowa State University. http://www.iowabeefcenter.org/.
Web sites verified 6/16/2020.
ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.
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