ST. CLOUD — We are all experiencing this widespread drought in most of Minnesota. For Stearns, Benton, and Morrison Counties we range from being labeled in a moderate drought warning all the way to severe drought. Looking at the dryland acres of corn, soybeans, and alfalfa in the area you can see the effects of this drought. From field visits and phone calls the primary concern at this moment is on corn silage. Here are some tips on harvesting drought stressed corn silage.
First you want to test the moisture level of the corn silage field in question. Silage moisture is an important factor in the ensiling process and using a rule of thumb method when dealing with drought damaged corn is not a great idea. Even if the corn looks fired up and dry it may still contain over 70 percent moisture. By properly testing your corn silage for moisture you can allow the plant to continue growing and maximize yields while still harvesting at the proper time. When testing for moisture it is important to get a representative sample from the field. You can use a koster tester or microwave to get the exact moisture level of the corn. You will want to do this often because once it becomes too dry silage will not pack well which of course increases the potential for air pockets and mold. While you can add moisture to dry corn silage it may take a large amount to bring back to a level that allows for ensiling. Keep in mind that it takes 7 gallons of water per 1 ton of silage to raise the moisture level 1 point. The recommended moisture levels for the different storage options of corn silage are stated below.
55-60% for upright oxygen-limiting silos
60-65% for upright stave silos
60-70% for bags
65-70% for bunkers
Another concern for harvesting drought-stressed corn silage is the level of nitrates in the corn silage. In drought conditions, nitrates accumulate in the lower one-third of the stalk. While you can raise the cutting deck to a height of 10-12 inches to avoid that accumulation, yields will drop. The entire plant nitrate concentration should factor into the decision of cutting height. Harvest should also be delayed following a rainfall event as a flush of nitrates will enter the plant temporarily increasing nitrate concerns. The end goal should be to ensile it. If ensiled properly, you should lose anywhere from one-third to one-half of the nitrates as a gas. However, testing the feed after being ensiled is a good idea so you know what you are dealing with. Green chopping drought stressed corn is not recommended as nitrates will be higher in that material.
Chopping length also plays a role in the ensiling process. The theoretical length of cut for processed corn silage is ¾ inch and if not processed the length should be ¼ to ½ inch. If harvesting corn silage that is drier than recommended, decreasing the cutting size may help with packing. Using a proven inoculant may also increase the chances of successful ensiling. With reduced yields our margin of error is smaller this year than most, meaning that we need to squeeze as much out of each acre as we can.
Finally, on the safety front, remember to be cautious around silage gasses, it is very toxic to people and animals. Follow the pre-harvest interval for grazing restrictions listed for any pesticides used on the field.
If you have questions on the above information, please feel free to email firstname.lastname@example.org, or call at 608-515-4414. To receive future events, educational programming, and agronomic updates by email, signup at z.umn.edu/tricountysignup.
— Emily Popp, University of Minnesota Extension
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