Chopping drought-stressed corn into silage for dairy feed may be the most viable option for many growers this year, but Michigan State University Extension educator Faith Cullens says harvesting and feeding drought-stressed corn silage comes with some caveats.

To determine the correct harvesting time, Cullens says moisture is the key. The whole plant moisture should be 60 to 68 percent at harvest for ideal fermentation. Drying leaves of dying plants actually can impede plant dry down because moisture no longer can exit the plant via leaves, and stalks can retain moisture extremely well. She says mowing and wilting of plants that are too short to feed into a chopper can help enhance drying to an appropriate moisture level for ensiling. However, she cautions that this practice will introduce significant soil into the forage, thus increasing ash content and introducing greater levels of Bacillus and Clostridia bacteria, which could interfere with fermentation.

Nitrates are a serious concern in drought-stressed corn, and Cullens says ensiling is a good way to abate the risk of nitrate toxicity. Nitrates levels can be reduced 20 to 66 percent by ensiling.  Harvesting corn 12 inches above the ground also will reduce nitrates, but also will reduce total forage yield.

Cullens says it is essential to test corn silage nitrate levels before feeding. Most commercial labs offer nitrate testing for $15 per sample or less. Feeding guidelines for dairy animals are to keep nitrate levels below 0.4 percent of the  total ration, and taking extra care with pregnant animals. 

If ensiling drought-stressed corn silage in upright silos, Cullens advises exercising extra caution with nitrogen dioxide produced during fermentation. This deadly gas will be produced within two hours of ensiling and can remain for two to three weeks. Concentrations as low as 25 ppm are invisible, odorless and toxic to humans. At higher concentrations, the gas is yellowish-brown and smells like bleach. If it necessary to enter a silo before three weeks of fermentation, run the blower fan for at least 30 minutes before entry, and leave it running while inside. Using a self-contained breathing apparatus also is highly recommended.

Read more of Cullens’ advice on managing drought-stressed corn silage.