Drought Corn
A high-yielding corn crop requires about 22 inches of water, with a range of 20 to 25 inches. About 15 to 16 inches of water is enough to produce a low yield, but that depends on when during the season the water is available or unavailable. In general, higher yields need more water, but factors such as temperature affect this to some extent.
There are several variables to consider when deciding how to manage corn after a drought. For purposes here, we will define “drought” as severity and timing of dry weather that results in reduction in corn yield to less than one-half the expected yield. If you have crop insurance that covers drought, consult your insurance company before you harvest the drought-stressed crop. If there is a market for using such corn for silage, many people prefer to do that, because silage value depends less on grain yield. It is important not to wait too long to cut such silage—moisture content should be around 65%, depending on storage structure. Expect yields of around 1 ton (of 65% moisture silage) per foot of corn plant cut. If silage is not an option, grain should be harvested if the grain yield is high enough to pay the harvest, drying, and storage costs. Corn grain quality in such cases depends on whether dry weather limited pollination and seed number, or whether the drought limited the amount of filling, and so final kernel size. Some drought-affected corn grain may have a light test weight due to inadequate starch deposition. Kernels may also retain some sugars, which can darken as grain is artificially dried. Both low test weight and “heat-damaged” kernels can lower the price of corn grain. Because starch is deposited later than protein in the kernel, less starch may mean higher protein levels, and such grain might have more value as livestock feed than as cash grain.
If grain yield is inadequate to pay these costs, and the insurance company concurs (some might even request this to prevent harvest), it might make sense to disk the crop to prevent weed growth and to start the breakdown of crop residue. If corn is planted the year following the drought, it usually benefits from having less crop residue to contend with and, unless the weather in the fall and spring is unusually wet, carryover nitrogen from the drought-affected crop should be available for the next crop. In northern states, remaining N is estimated by subtracting the yield (in bushels) of the drought-affected corn from the amount of N fertilizer (lb N) applied to that crop, and taking half of this difference as the amount of N available to the next crop. Rainfall and warm temperatures in southern states will normally cause all N to be lost.
For more information on this and other topics related to corn production, contact your state extension corn specialist or your local extension educator/agent.
Following is the link to the corn extension specialists: state extension corn specialist.
