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Corn Development and Dry-Down in 2017 (09/14/17)

After a relatively cold August and a colder than average start to September, the questions being asked by many corn growers are, when is my corn going to mature and when will it be dry enough to allow for harvest.

Corn Development and Dry-Down in 2017

After a relatively cold August and a colder than average start to September, the questions being asked by many corn growers are, when is my corn going to mature and when will it be dry enough to allow for harvest. Accumulated corn growing degree days (GDDs) can be a good predictor of corn development, and from a quick look at NDAWN, these accumulations are running slightly ahead of the long-term average for the western two thirds of the state and well below average for the eastern third of the state. In the southeastern corner of the state in particular, GDD accumulations range from 100 to 239 GDDs behind normal. The same region is running 150 to 345 GDDs behind last year, which was an exceptionally good year for corn development and dry-down. I used the U2U Decision Support Tool – Corn Growing Degree Days (https://hprcc.unl.edu/gdd.php#), to predict when corn hybrids of differing maturity will reach black layer this year in a few areas of the state (see Table 1 on next page).

This tool was developed by a group of researchers from land grant institutions in the mid-west and can be used to estimate corn maturity date anywhere in the region (point and click on a location in a map) for a range of hybrid relative maturities and planting dates. These predictions use average weather data for future weather, so their accuracy will be influenced by future weather that is warmer or cooler than average. These data show that corn will mature more than a week later than last year for most areas of the state. For the various scenarios described, they further suggest all except the later maturing hybrids should reach physiological maturity (black layer) unless we get a killing frost within the next two weeks.

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How quickly will corn dry is the second concern, as this will dictate harvest date and the amount of on-farm drying that will be needed. A rough rule of thumb is that it will take at least a month to dry corn after reaching black layer to the point that harvest can begin. However, the actual rate of drying is impacted by the moisture of the corn and weather factors such as relative humidity, temperature and wind speed. In 2016, we found corn to dry at the rate of about 0.75 percent per day for the period mid-September to mid-October. This rate was exceptional, as in other years we have found the rate to be more in the order of 0.25% to 0.33% loss per day for that same period. If we have near normal weather the remainder of this season, we can probably expect corn to reach the harvest moistures achieved last year in the eastern part of the state more than a week (and probably more like two weeks) later than the last two years. Warmer than normal weather will obviously hasten the process. Some potentially good news is that the most recent three-month climate outlook by the National Weather Service predicts that temperatures for the next two months will be probably be above normal.

Joel Ransom

Extension Agronomist for Cereal Crops

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