Frost damage to corn and soybeans
Freezing temperatures before physiological maturity will damage corn and soy. Maturity in corn occurs when kernels form a black layer at the kernel tip, grain will be at approximately 30 to 35 percent moisture. Maturity in soy occurs when beans in pods turn yellow and are no longer green. After maturity, no additional dry matter will be accumulated in the seed.
In addition to creating quality problems, premature frost will reduce the yield of dry grain.
Characteristics of frost-damaged corn include small, misshapen soft kernels and undeveloped starch structure. Recognize that these effects are progressive, with least impact on corn closer to maturity. Animal feed is also the best use for frost-damaged corn.
Characteristics of frost-damaged soy include green or elongated yellow soy that shrink to smaller than normal size after drying and slower field dry down.
Soy often loses their green color within two weeks of maturity, so allow field dry down if at all possible. This same statement is true of plants that were only partially frosted (generally on upper leaves). Processors will discount green soy based on the color definition in the US Grades. The greenness of immature soybeans must be refined out of the oil.
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Article made possible through the contribution of Iowa State University.