Drought-Stressed Corn for Silage

Dr. Bill Weiss, Dairy Nutrition Specialist, The Ohio State University 

The dry conditions in many parts of the State have greatly reduced hay and haycrop silage yields, which has reduced forage inventory on many dairy farms. In addition, corn plants are becoming stunted and grain yields are likely to be poor. Low forage inventory and the desire to salvage some value from corn fields means that much of the drought-stressed corn in the state will be chopped for silage. Drought-stressed corn silage can be a good feed for dairy cows and other ruminants if some guidelines are followed.

  1. Chop at the correct dry matter: 30 to 38% dry matter. Corn plants, whether drought-stressed or not, must contain the proper amount of moisture for good fermentation in the silo. Corn plants that are chopped with less than about 30% dry matter (especially less than 27% dry matter) are at high risk of a poor fermentation (high acetic acid, low pH, etc). Corn plants chopped with much more than 38 to 40% dry matter usually undergo a limited fermentation and can mold and spoil during storage and feed out. Drought-stressed corn often is much wetter than normal corn because normal corn has more kernels and kernels are drier than the vegetative part of the plant. Before chopping drought-stressed corn for silage, cut some stalks and run dry matter analysis. If the crop is too wet to make silage, do not chop. Forage supplies are likely to be very tight this fall and winter. Do not exacerbate the situation by chopping at the incorrect dry matter concentration and making poor quality silage. Even under severe drought, it is extremely likely that corn plants are too wet to make into silage in mid-July.
  2. Nitrates might be a problem and greenchopping corn plants is not recommended. Silage fermentation can greatly reduce nitrate concentrations. Therefore, very often silage is safe to feed even though the plants would have been toxic if fed fresh. If greenchopping must be done because of limited forage supplies, set the chopper high because nitrates accumulate in the lower portion of the stalk.
  3. Nutrient value of drought-stress corn silage can be fairly high. Compared with normal corn silage, drought-stressed corn silage usually has 1 to 2 percentage units more crude protein, 10 to 20 percentage units more neutral detergent fiber (the fewer the number of ears, the higher the fiber concentration), and 15 to 25 percentage units less starch. Even though fiber concentrations are high and starch concentrations are low, energy values (TDN, net energy, etc.) of drought-stressed corn are usually 90 to 95% as high as normal corn silage because the fiber is highly digestible. The bottom line is that if drought-stressed corn silage ferments properly (see point #1), it is quite acceptable as a forage for even high-producing dairy cows. However, the nutrient composition of drought-stressed corn will be more variable than normal corn silage and it must be sampled and analyzed for nutrient composition and diets balanced accordingly.