The following answer was provided by Mike Hutjens, professor of animal sciences emeritus at the University of Illinois.
Q: This year, we will be faced with drought-stressed corn (early corn that tasseled with no pollination to late corn that is only three feet tall and not tasseled). What strategies and alternatives can be considered?
A: With 12 percent of the United States classified as “exceptional drought conditions,” as of early July, dairy managers and grain producers are watching thousands of acres of corn that is experiencing yield and quality reductions. Dairy managers are planning strategies if timely rain does not arrive soon (in some areas, it is too late).
Corn plants are firing (drying) from the roots up the stalk of the corn plant. Some corn is tasseling which may not pollinate, resulting in barren corn stalks (no ears). Other cornfields are in various stages of growth from 3 to 6 feet in height.
The following strategies can be considered when facing these challenges.
- If corn plants have green active tissue, the plant may recover and produce more plant dry matter or yield per acre if rain arrives. Do not harvest too early.
- Immature drought-stressed can appear dry and dead, but may contain more than 70 percent moisture in the stalk. For optimal fermentation, ensile when the chopped material ranges from 30 to 38 percent dry matter, depending on type of storage (in a bag, bunker, and piles can be wetter while upright storage must be drier).
- If the corn plant has not pollinated and is barren, the quality and yield of the corn silage dry matter will be reduced, but the plant may continue to store nutrients if green.
- Drought-stressed corn can be high in nitrates. Field values as high as 17000 ppm (1.7 percent) has been measured in commercial Illinois labs. Levels over 4400 ppm (parts per million) require feeding adjustments. Values over 17,600 ppm (in the total ration dry matter) should not be fed to dairy cattle. If results are expressed a nitrate-nitrogen, the values will be 4.4 times lower (For example, 4400 ppm nitrates is equal to 1000 ppm nitrate nitrogen).
- Fermenting corn as silage can reduce nitrate levels by 25 to 40 percent. Ensiling corn is a recommended practice, but green chopping or pasturing can be risky. Baling corn silage as hay or baleage will similar to grass hay quality when the corn plants are immature. No nitrate changes will occur when produced dry hay.
- Adding a silage inoculant is recommended to improve fermentation, as natural occurring bacteria may be low. Do not add urea or limestone, as it can slow down fermentation.
Drought stress corn silage can contain 60 to 80 percent of corn silage nutrient value depending on the stage of maturity. One guideline is each foot of corn plant may yield one ton of dry matter (varies depending on stage of maturity). Testing the harvested drought-stressed corn silage after ensiling can measure nutrient content and nitrate levels. Dairy producers may be able to purchase drought-stress corn locally, as it has little value for grain producers. Drought-stress corn silage may be an alternative locally as the fertilizer value of the corn stalks represent $35 to $40 a ton in the field (need to add in harvest costs).