Field drydown of late planted corn in northern Michigan

Identifying black layer and the milk lines in kernel development

Excessive spring rains delayed corn planting in some areas of central and northern Michigan. There were a number of fields that were planted in mid-June. The late planting was followed by cooler than normal temperatures, and has many farmers wondering if their corn crop will make physiological maturity or black layer prior to a killing frost. High grain moisture at harvest will increase drying costs and reduce net return. Harvesting this as high moisture corn, or as corn silage and using it for livestock feed, may be the best opportunity that exists. Exceptionally favorable fall weather is giving these late planted fields the opportunity reach maturity and dry down to an acceptable level prior to harvest, but that is not a guarantee, and Michigan State University Extension highly recommends making alternate plans.

Most corn hybrids grown in Michigan need about 50 to 60 days after pollination to reach maturity. Kernel moisture content decreases as the kernel develops through the blister stage (about 85 percent moisture), milk stage (about 80 percent moisture), dough stage (about 70 percent moisture), dent stage (about 55 percent moisture), and physiological maturity/black layer (about 30 percent moisture). As corn kernels develop, the starch or milk line moves down from the top of the kernel to the bottom. Before maturity the kernel losses moisture from a combination of water loss and the accumulation of dry matter because of the grain fill process. Once physiological maturity has been reached and the black layer identified, kernel moisture will continue to decrease primarily due to water loss from the kernel.

Grain drydown is quicker when temperatures are warmer so it is stands to reason that corn maturing in late Aug. will dry faster than corn that matures in late Sept. or early Oct. There is a close relationship between the date when the grain gets close to physiological maturity (half milkline or 2-3 weeks prior to blacklayer) and the average daily drydown rate. The average drydown rate will vary from about 0.08 percentage points per day for grain reaching maturity in late August to about 0.4 percentage points per day for grain that reaches maturity in Late Sept. or early Oct. Keep in mind that grain moisture loss will vary depending on temperature, humidity, sunshine or rain conditions for each day. It is not uncommon to for grain moisture to decline one percentage point per day when the weather is warm, sunny, windy and dry.

Weather conditions and corn variety strongly influence in field drydown. Selecting varieties with superior yielding ability, appropriate maturity for your region, as well as quick drydown will provide for maximum return on corn production acres. For more information on this topic, contact Michigan State University Extension Educators, Paul Gross at 989-772-0911 Ext. 220, or Kable Thurlow at 989-426-7741.

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