With the high cost of diesel fuel, the high cost of propane for drying grains, and the Port of New Orleans currently closed, many producers are wondering if they should delay harvest.

Kurt Thelen, crop and soil scientist with Michigan State University, says delaying harvest beyond optimum crop harvest moisture usually results in yield loss. The optimum grain harvest moisture to maximize crop yield is generally considered to be between 13 percent and 15 percent for soybeans and approximately 25 percent for corn.

Crop yield loss at harvest can be categorized as field loss (sometimes referred to as pre-harvest loss) and machine loss. Field loss is grain that never makes it into the combine, including ear drop and seed shattering from the standing crop, along with grain left behind and not picked up by the combine header.

The table below shows the yield loss for corn associated with delayed harvest. The data were collected from several Midwestern states over several years.


Harvest month October November December
(Yield loss) Machine loss 4.6% 7.0% 11.8% Total loss 5.0% 8.4% 18.4%

As a general rule, says Thelen, finding two kernels of corn or four soybean grains per square foot in the field is equivalent to a one bushel per acre loss in yield. Be sure to measure your anticipated savings from delaying harvest against the yield losses you could incur.

For even more help, there’s a spreadsheet to help determine when to harvest:

Sam McNeill, Extension agricultural engineer at the University of Kentucky, has developed a helpful tool that can help you decide when to harvest. Available as an Excel spreadsheet, or in a PDF form that you can print off, it estimates the optimum moisture level to harvest crops based on a range of energy-cost scenarios.

You can access the free tools online at: http://www.bae.uky.edu/ext/Grain_Storage/Calculators/