Recommendations for Late Season Grain Harvest

By Sam McNeill, Extension Agricultural Engineer, University of Kentucky 

Estimates indicate that nearly 10% of the corn crop and 30% of the soybean crop in Kentucky are yet to be harvested, which is behind previous years but typically seen across the US grain belt this year. Field drying has slowed considerably, and most late planted crops are still above moisture levels that are considered safe for storage. Thus, farmers are faced with the cost trade-offs between drying and elevator discounts for high moisture grain if delivered directly from the field. One bit of good news is that LP gas prices are lower than in previous years, so drying costs are lower and may be recovered by savings in high moisture discounts.  

For example, with this season’s energy prices it would cost between 2 to 3 cents per bushel to remove a point of moisture from grain in most drying and handling systems. Additional costs for hauling can vary widely, but generally range between 5 and 15 cents per bushel for modest distances. Combining these costs for 5 points of moisture removal amounts to 15 to 30 cents per bushel (3 to 6 cents per point of moisture). This cost should be compared to moisture discounts at the elevator, which are applied to grain above a specified base moisture (typically 15.0% or 15.5% for corn and 13.0% for soybeans), and stated as either a direct cost (cents per point of moisture) or percent of gross weight (for example 3%).  

Several farmers, extension agents and crop consultants have asked about field drying rates this late in the season. Several average daily weather variables (temperature, relative humidity, solar intensity, rainfall, wind speed, degree day and pan evaporation) affect field drying, but a reliable model to include them all has yet to be developed. However, a fair prediction of grain moisture can be estimated by calculating the equilibrium moisture content based on average outdoor temperature and relative humidity. A quick comparison of the average conditions observed and predicted from November 8 to 25 for Lexington and Paducah are shown in the table below along with the corresponding equilibrium moisture for corn and soybeans at both locations. These values for grain moisture are the minimum levels that would be expected at each location this year for grain that is drying in the field or in a bin with unheated air.  

Table 1. The lowest expected field moisture content of corn and soybeans based on averaged observed and predicted weather from November 8 to 25. The lowest expected moisture content is the equilibrium moisture content (EMC).

Interestingly, this approach predicts a moisture loss of about 0.1% per day for corn and 0.2% per day for soybeans at both locations during this period. However, different weather conditions would influence these rates and extended cloudy, damp periods would actually add moisture to grain, so it should be harvested quickly to reduce that risk. 
More information on soybean harvesting, drying and storage can be found on the University of Kentucky Grain Storage website (www.uky.edu/bae/grain-storage-systems).