Some of the guidelines and strategies for harvesting corn silage do not apply when the crop is stressed by drought. Some crops have taken a double or triple whammy this year – potentially a combination stressed by wet weather early in the growing season that limited growth, hail in some areas and drought that may be worsened by limited early season root development. There may be opportunities for neighbors to help each other where crops are damaged in localized areas. A neighbor with extra corn might consider selling some for silage to help meet the needs of livestock producers. It is also important to check with crop insurance carriers for any procedures that may need to be followed to document crop losses. Whole plant moisture is probably the most important indicator for when it’s time to chop corn silage. The North Central Regional Extension Publication suggests harvesting when the whole plant moisture is 60 percent to 65 percent for upright silo, 50 percent to 60 percent for upright oxygen limiting silos, 65 percent to 70 percent for bunkers and piles, and 60 percent to 70 percent for bags. Other sources may have recommendations that vary a point or two. Past experience with your own storage systems is an important consideration. Field variations Variations in field conditions because of drought stress are challenging. Dry spots in a field can test 50 percent moisture while normal areas could still be above 70 percent. It’s hard to tell if you have a uniform mix that is on target for your storage. It won’t necessarily reach a uniform equilibrium in a silo or pile either. You can make use of any logical opportunities to select rows or parts of the field, but obviously that’s not always practical and the results are uncertain. If need be, put dryer material in the bottom of a silo or in the deepest part of a pile or bunker. Placing wet material on top will improve packing. Manage for the adjustments and challenges this will require in feeding milk cows. Nitrates The NCR publication says high nitrate levels are found most frequently where high nitrogen rates were applied, or where drought-stressed crop is chopped within three days following a significant rain. Making silage from a crop that is suspected to have high nitrates is preferred to green chopping because the fermentation pro-cess will decrease the nitrate levels by about 50 percent. When in doubt, have a fresh-chopped sample analyzed and allow for this factor, and/or analyze the silage before feeding. High nitrate feed material can be diluted in the total ration with other ration ingredients. A 1986 Michigan State article suggests that in most situations, the nitrate level in feed must be over 2 percent nitrate nitrogen to cause a problem. They also suggest raising the cutter bar to leave a 10-12 inch stubble because nitrates tend to accumulate in the lower portion of the stalk in drought-stressed corn. Under drought conditions where feed supplies may be limited, it seems good to test the crop and to consider the dilution possibilities before leaving more crop in the field. It is generally thought that if the crop grew to a fairly normal height and produced a somewhat normal ear, nitrates are not likely to be a problem. The Michigan article suggests that drought-stressed corn silage should be introduced into the ration slowly to allow rumen bacteria to adapt. Gradual ration changes are always advised for this reason. Silo Gas Nitrogen dioxide is the most deadly component of silo gases that are present during the fermentation process. As a nitrogen compound, it is logical that this could be more of a hazard with drought-stressed crops or under other conditions where a higher nitrogen content may be present in the crop. Hazardous levels can be present within the first 24 hours as well as for 2-3 week after filling silos. The best strategy is to stay out of silos for 2-3 weeks and ventilate the silage and silo room thoroughly when the silo is opened. Source: Dan Martens, Benton County Regional Extension Educator. Submitted by Dave Schwartz.
