NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
September 14, 2000
Denise McWilliams, extension crop production specialist for North Dakota State University and the University of Minnesota, responds to late season questions from corn producers.
Q.What really determines the severity of frost damage on corn?
A. The duration and extent of below freezing temperatures will determine the damage received.
Q. When does tissue damage occur versus actual kill of corn tissue with a freeze?
A. Over four hours of temperatures below 32 degrees can result in tissue damage on a corn plant that can be detrimental. Quick kill of the corn plant will occur with four hours of temperatures at or below 28 degrees. Individual plant conditioning and placement in the field, particularly whether the plant is in a low or high spot in the field, may also moderate the temperature conditions and effects.
Q. With a frost, will absolutely no more grain fill continue?
A. It depends on how much leaf and stem tissue is killed. If only a portion of the leaves are killed on a plant, the rest may still be able to continue to increase grain yield with returning good weather conditions.
Q. Does timing of a frost on a corn plant affect test weight as well as yield?
A. Yes. The later the maturity of the corn crop the less effect frost has on corn yield and corn test weight.
Q. When is corn completely safe from damage from a frost?
A. Corn at physiological maturity, or when the black layer has formed in kernels, will not have any yield reduction from a frost.
Q. Is there a decrease in kernel dry-down after a frost in corn?
A. This question has often been answered both ways in research, but more recent studies have shown that kernel moisture loss may not decrease after a frost. Instead, other conditions such as a tight husk or even specific hybrid type may have more to do with any slowing of dry-down in corn following a frost. Also, remember that temperature and relative humidity of surrounding air also may influence kernel dry-down in corn.
Q. Can you make silage from frosted corn?
A. Yes. Carefully consider the corn maturity to determine if silage is a possible route for frosted corn. Optimum silage is cut at around 62 to 68 percent moisture. If the corn is at only the milk stage, the whole plant moisture level is high so that silage will be very wet and will sour quickly. Nutrient loss will be high in storage and livestock consumption will be low. Consider letting corn at the milk stage dry down below 70 percent in the field or consider adding edible absorbent materials such as ground grain or straw in the mix. The dough stage of corn is also too wet for good silage and proper storage. The best time for silage is at mid-milk line (past initial dent) when whole plant moisture content is around 68 percent. Value of silage depends on use or probability of sale. In general, pricing will be low as a quick rule of thumb is to multiply the current price of corn grain by six to determine the rough value of a ton of silage, and then subtract out harvest costs for your final value.
Q. My corn was frozen during the milk stage (kernel moisture is around 80 percent), will the grain still be okay?
A. Yield potential for grain will be very low. In fact, you probably will obtain less than half of your expected yield from the stand. Also, the grain will be very chaffy and kernels will shrink readily when dried down by heat. Green-chopping or ensiling may be a better route, although by no means optimum.
Q. How much yield can I expect if my corn crop is in the dough stage (70 percent kernel moisture)?
A. Your yield reduction will be 35 to 50 percent of the expected yield from a crop that had made it to black layer or physiological maturity.
Q. My corn just dented when the killing frost came through my field. Will I have any yield loss?
A. Yes. Yield reduction at dent will be 10 to 20 percent.
Q. My corn dented and the milk line was half-way down on the kernel. Did I get any yield loss from the killing freeze?
A. At mid-milk line, the kernels are at about 40 percent moisture and close to maturity, but 4 to 5 percent yield loss should be expected.
Q. Will I have any problems with my corn if it reaches physiological maturity and harvest moisture, but I can't get out to harvest it?
A. Delayed harvest may result in loss of yield due to seed or ear loss and stalk lodging. Some loss of quality may also result with lower bushel weight and deteriorated grain due to field weathering.
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NDSU Agriculture Communication
Source: Denise McWilliams, (701) 231-8160
Editor: Gary Moran, (701) 231-7865