Decision Tool Predicts Local Field Drying Trends for Corn

By Sam McNeill

Pre-harvest USDA estimates pegged Kentucky’s corn crop at 200 million bushels this year (28% below 2021) and it’s off to a similar, slow start. This week’s USDA report showed the progress of corn harvest at 10% complete statewide, which is about the same as this time last year, but about half the 5-year average (~20%). On a positive note, field drying should have good potential across most of the state next week, so many farmers will likely ramp up harvest, quickly catch up to the 5-year average, and benefit from lower drying costs.

A web-based tool has been developed at Clemson University to calculate the equilibrium moisture content of grains at predicted temperature and relative humidity conditions with embedded equations. The Clemson EMC Calculator pulls data from the National Weather Service that is available for each zip code and is reported at 3-hour intervals. Once logged in, the user enters the zip code and selects the type of grain and an equation to calculate corresponding grain moisture values at 3-hour intervals. Graphs are then shown for each variable during the period along with a table.

The EMC calculator was used to predict moisture changes of mature corn at four locations across Kentucky’s production area for the next five days. Data from the output table was imported into an Excel spreadsheet to generate a trendline at each location and is shown in Figure 1. Since grain moisture doesn’t change instantaneously, but lags in response to ambient conditions, this approach provides an indicator to illustrate whether conditions will favor drying or re-wetting during the period. Similarly, it can be used to guide harvest decisions for mature crops.

From September 13 to 18, the Clemson EMC Calculator predicts a grain moisture loss of about 2 to 3 percentage points for Mayfield, Madisonville, Elizabethtown, and Lexington, KY, owing largely to the mild temperatures and below-average relative humidity levels (Table 1). Bear in mind that this model provides an indication of either drying or re-wetting in the vicinity and does not account for cloud cover, wind speed, or rain showers. Still, it can be a useful tool to predict changes in grain moisture for your area and can be accessed at Clemson

EMC Calculator: https://precisionag.sites.clemson.edu/Calculators/Grain_Storage/EMC_Calc/

Table 1. Average ambient conditions in Mayfield, Madisonville, Elizabethtown, & Lexington from September 13 to 18, 2022.