Page Title

Northwest ND (09/08/21)


Corn Dry Down In 2021

With the exceptionally warm and dry conditions of the 2021 growing season, corn is drying down quickly across most of the state. In areas where the drought was Extreme or Exceptional, much of the corn that failed to tassel or produce an ear was chopped or baled a month or more ago in many cases. Early-maturing varieties have already reached black layer in many areas but later hybrids may still have a few days or weeks left to go. After reaching black layer, corn kernels do not add additional dry weight and lose water weight, i.e., moisture, through evaporation. The 2-4” of rain that has fallen in the past two weeks in eastern portions of the state may help increase the test weight of later maturing varieties that have not yet reached black layer, but will not contribute anything to yield for early maturing varieties that had already reached black layer by mid-August.

Growing degree accumulations have been greater than last year. Below are 2021 and 2020 GDD as of September 6th for a May 1st planting date for select locations according to the NDAWN Corn Growing Degree Day calculator, found here:


2021 GDD

2020 GDD

Difference (2021-2020)

Grand Forks













If you want to predict when your corn hybrids of different maturity will reach black layer, try the U2U Decision Support Corn GDD Tool developed by researchers from land grant universities through the High Plains Regional Climate Center (HPRCC) found here: This tool can be used to estimate corn maturity date anywhere in the mid-west region by pointing and clicking on your county in the map. Then, select your planting date and corn maturity days in the drop-down menus. The tool will then automatically generate a graph showing GDD accumulation for the current year and project it forward based on average weather data for future dates. As an example, below is the graph generated for a May 1 planting date of a 95 day hybrid in Cass County.

Corn growing degree day tool chart.png


According to this scenario, black layer is predicted to occur on September 5th after 2280 GDDs have been accumulated. You can see how this year’s line (the green line on top representing 2021) is higher than the purple line (the average GDD accumulation 1981-2010). In a more average year, black layer GDDs would not be reached until September 26th. Hopefully our warmer-than-average growing season will continue to allow for good dry down conditions and a timely corn grain harvest.


Clair Keene

Extension Cropping Systems Specialist

NDSU Williston Research Extension Center