Use Drought-Stressed Corn as Hay or Silage

BROOKINGS, S.D. -- Producers can use drought-stressed or immature corn as hay or silage when harvested.

That's according to South Dakota State University Extension Beef Specialists Cody Wright and Kent Tjardes.

"Drought-stressed corn can serve as a roughage source for cattle, but proper harvesting and processing is essential," Wright said.

Silage: The optimal time to harvest corn for silage is when the plant moisture is between 60 and 70 percent (30 to 40 percent dry matter). Producers should have the moisture checked because it can be highly variable drought-stressed corn. Immature and barren plants could contain more moisture than under normal circumstances. Excess moisture may lead to poor fermentation, resulting in high levels of butyric acid or "sour smelling" corn silage.

Drought-stressed or immature corn tends to have higher crude protein levels than normal corn silage. The energy value of drought-stressed corn can range anywhere from 65 to 80 percent of the energy value of normal silage, Tjardes said. This will depend on how much grain filling occurs, how digestible the fiber remains, and how much sugar remains in the stalk. Regardless of stage of maturity, silage should be analyzed to assess the nutrient composition. Samples should be collected at least 21 days after ensiling to allow enough time for proper fermentation.

High levels of nitrates can accumulate in drought-stressed corn. Nitrates generally accumulate in the lower one-third of the corn plant; thus, if possible, it is desirable to leave the lower eight to 12 inches of the stalk.

Sampling standing crops is extremely difficult and potentially inaccurate, thus silage samples should be analyzed for nitrates. Proper ensiling may reduce nitrate levels by 20 to 60 percent. Rainfall may also help reduce nitrate levels by promoting plant growth. If there is some rain and subsequent regrowth, silage harvest should be delayed for five to seven days.

"High nitrate silages may also present a human health risk," Wright said. The deadly gases, nitrogen dioxide, a reddish-brown gas, and nitrogen tetroxide, a yellow gas, can both be formed during the ensiling process. The greatest danger is 12 to 72 hours after filling the silo. Both gasses are heavier than air and can remain in the air mass over the silage or in the unloading areas. Use extreme caution when working in and around any silo.

Do not add any non-protein nitrogen (such as urea or ammonia) to drought-stressed corn silage. This can cause an elevation in nitrate levels. In some cases, adding a bacterial inoculant may assist in a rapid and effective fermentation. Preservatives may help effectively store the hay. However, they will not alter the nitrate levels.

Hay: The sooner corn can be harvested as hay, the better the forage quality will be. Keep in mind that barren corn is basically coarse grass. Therefore, harvesting must include crimping or some other mechanical processing to help facilitate field curing. Seven to 10 days may be required to effectively cure the corn to the desired moisture.

Depending on the cost, wrapping or bagging bales may be the most desirable option for harvesting drought-stressed corn. Wrapping or bagging bales allows the baled corn to ensile; thus improving feed value and reducing nitrate levels, Wright and Tjardes said.

The nutrient composition of "corn hay" will decrease as the plant continues to mature. Energy and protein values will likely fall into the same ranges as most medium to poor quality forages. However, sampling the harvested forage is definitely the best way to assess the nutrient composition and nitrate levels.

In contrast to silage, high nitrate levels in corn, harvested as hay, will remain in the feed. Some reduction may occur if bales are wrapped or stored in bags. However, this will be dependent upon the degree of fermentation.

Forages with low to moderate nitrate levels need not be discarded as a feed. It is possible to dilute the nitrate levels by blending the high nitrate feeds with those containing lower nitrate levels.

More information on drought and nitrate toxicity may be found at the SDSU drought Web site at http://sdces.sdstate.edu/drought/. More information specifically for livestock producers is at an SDSU Department of Animal and Range Science Web site, http://ars.sdstate.edu/extbeef/Drought_Management.htm or contact any county Extension office.

Contact: Cody Wright, (605) 688-5448; Kent Tjardes, (605) 688-5460
** For links to other sites showcasing SDSU's work in teaching, research, and Extension, visit http://sdces.sdstate.edu.

Lance Nixon, Editor
AgBio Communications Unit
South Dakota State University
ACC, Box 2231, Rm 200
Brookings, SD 57007
Telephone: (605) 688-4653
Lance_Nixon@sdstate.edu