Looking at the dryland acres of corn, soybeans and alfalfa, you can see the effects of 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.

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 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 it back to a level which allows for ensiling. Keep in mind it takes seven gallons of water per ton of silage to raise the moisture level one point.

The recommended moisture levels for the different storage options of corn silage are 55-60 percent for upright oxygen-limiting silos; 60-65 percent for upright stave silos; 60-70 percent for bags; and 65-70 percent 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 three-quarters of an inch; and if not processed, the length should be a quarter to half an inch. If harvesting corn silage which 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 gas. 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, email Nathan Drewitz at ndrewitz@umn.edu, or call (608) 515-4414.

This article was submitted by Emily Popp, University of Minnesota Extension.

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