Last week I wrote about the harvest of immature corn as silage with a focus on plant moisture content. This week I will cover other best management practices to achieve good quality corn silage for both immature and our normal, mature corn plants. As mentioned last week, good quality corn silage is dependent upon the lactic acid producing bacteria population dominating the fermentation process and quickly dropping pH below 4.5 to stop the activity of harmful yeasts, molds and clostridia organisms. This requires correct plant moisture and anerobic conditions.
The outer limits of plant moisture content for silage production range from 60 % moisture or 40% dry matter (DM), to 70% moisture or 30% DM. A moisture content of 65% or 35% DM is considered ideal for bags and bunker silos. Plant moisture content is most accurately determined by sampling 3 to 5 plants from several locations within a field and chopping those plants to one-half inch or less pieces as soon as possible after removal from the field. Mix the contents thoroughly and pull a 100-gram sample that can be dried in a microwave oven to determine the moisture content. For those that need it, I can provide a detailed procedure on how to correctly use a microwave oven to determine forage moisture content. Well-eared corn plants generally dry down about 0.5% percentage points per day during warm, dry weather.
Anerobic conditions are created by packing silage and creating a density that excludes air. There are two factors that directly affect the packing characteristic of ensiled forage, moisture content and particle size. Forage material that is too dry, especially above 38 to 40% dry matter or less than 60-62% moisture, does not pack well. There are likely to be air pockets and mold. Forage chopped with particle length that is too long also does not pack well. Recommendations for theoretical length of cut for a processed corn silage is ¾ inch and for non-processed corn silage the recommendation is ¼ to ½ inch.
Kernel processing breaks up corn kernels, allowing rumen bacteria more access to kernel starch, translating to more energy provided to the ruminant animal. One check that can be used for processor adjustment during the silage harvest is to fill a 32-ounce container with chopped silage and then spread that out on a flat surface. If there are two or less whole or half kernels of corn, kernel processing is ideal. Make adjustments if you observe five or more whole or half kernels. If corn is immature and/or only has a few ears or a small amount of corn grain, kernel processing is not necessary and could be detrimental to achieving good silage quality.
The goal is to pack the silage forage to achieve a density of 40 to 45 pounds of fresh forage per cubic foot. While most producers are probably not going to use this measurement, this density is most likely to be achieved when silage is packed in thin layers, no more than 6-8 inches per packing run. A commonly used guideline for packing weight is to provide 800 pounds of packing weight per ton of silage delivered. On-farm sampling of bunker silo density by researchers at Penn State showed that often the top layer of silage was not packed enough to get optimum fermentation and storage. The bottom line is that you can’t over pack silage. As Bill Weiss, Dairy Nutrition Specialist at OARDC says, “if you think you have packed enough, pack some more.”
In addition to packing, air exclusion during storage is critical to maintain silage quality. Consider lining the sidewalls of bunkers with plastic and cover the pile or bunker within hours after completing harvest and packing. Cover with plastic of 6 to 8 mil thickness, provide adequate overlap and weigh the 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.
Silage inoculants can help with favorable fermentation and help reduce losses during feed out. There are two main types of silage inoculants; lactic acid bacteria (LAB) and bacteria that produce acetic and propionic acid, bacteria species L. buchneri. Which to use? LAB inoculant promotes better silage fermentation and L. buchneri helps to reduce spoilage and feed out losses. Follow label directions. These are living organisms and mixing with chlorinated water or allowing water temperature to get too warm can kill the bacteria.
For more information about corn silage production, contact the Wayne County Extension office at 330-264-8722.
Rory Lewandowski is an OSU Extension Agriculture & Natural Resources Educator and may be reached at 330-264-8722.
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