With a fair amount of heat in South Dakota this summer, the corn crop is in very little danger of frost damage this fall. Temperature data for 2016 show that very few areas will be at risk of frost damage before black layer, or maturity, is reached in the corn crop.
Corn Growing Degree Day Tool
The Corn GDD tool from Useful 2 Usable has county-level temperature data that is used to calculate daily the growing degree days (GDD) for corn. This online tool is available to the public free of charge. At this time of the year, it could help inform marketing decisions to determine frost risk. This tool can also be used in the spring when selecting varieties for late planting or re-planting situations.
Sample Data: Brown & Minnehaha Counties
In this article, there are examples from two South Dakota counties, Brown and Minnehaha, to assess the current growing season. The planting date chosen was May 1. The Brown county example uses 95 day maturity (Figure 1), and Minnehaha county uses 103 day maturity (Figure 2).
In both counties, the current accumulated GDDs for 2016 (represented by the green line) are higher for this time of the year when compared to the average (purple line). The black dashed line is the projected future accumulated GDDs, which uses the current climate forecast for the next month and climatological averages thereafter. The vertical black line is expected black layer date, which is September 12 and 11 for Brown and Minnehaha counties, respectively.
Probable Frost Dates & Projected Maturity
The vertical dotted lines represent the range of probable frost dates. In this case, Brown county has some chance of pushing maturity into the typical frost season, as shown by the light blue lines. The average frost date is the tallest bar. Corn planted on/around May 1 with 95 day maturity would just edge into the frost season, if the remainder of its growing season was cool. The most likely scenario, according to historical data, shows this example corn crop to mature before the fall frost.
There is little risk of frost damage for Minehaha county, as even the latest date of projected black layer maturity ends at or before the earliest recorded frost in the last 30 years. A brief overview of other counties near Mitchell show that the heat of mid-summer has pushed that crop even further along, with no risk of frost damage this year with black layer maturity expected in early September.
As a result, it is anticipated that there is likely sufficient time for grain to dry in the field before harvest, which could save some money at the elevator if mechanical drying is not needed. Now we cross our fingers in the hopes of a favorable harvest season, with enough warm and dry days to harvest the corn crop this fall.