As the 2015 corn harvest begins, it is a great time to remind ourselves of the optimum harvest conditions and where harvest losses could occur around the combine. 

Harvest timing is normally based upon stalk quality, field conditions, ear drop and grain moisture. Optimum grain moisture at harvest ranges from 22-25%; at this moisture level, corn shells easily and standability is usually still acceptable. Corn standing in the field is drying down rapidly and there are many fields being harvested at grain moistures in the low 20s.  Waiting until corn dries down to below 19% can result in lower drying costs, but can lead to negative effects such as excess yield loss from mechanical issues (shattering or never getting into the combine) as well as ear drop and lodging. Harvesting dry corn is an advantage in lower drying costs but may increase yield loss from harvesting equipment.

Field drydown can lead to a 2-8% yield loss. This loss is caused by many different things such as header ear loss (usually driving too fast or too slow), header kernel loss (losses increase as moisture drops below 20%), cylinder loss (cylinder and rotor-speed breaking kernels) and separation loss (kernels passing over the sieves). Aside from yield loss, volunteer corn can be a concern the following year. Be sure to talk to your equipment manufacturer and read your combine manual to make proper adjustments in the field.

The following should be used as a guideline to determine harvest loss by harvesting equipment:

2 kernels/square foot = 1 bushel per acre (Iowa State University Field Guide)

4 soybeans/square foot = 1 bushel per acre

Laura Johnston, CCA-ON, Maizex Seeds Yield Specialist, West Elgin County
Twitter: @lmjohnston8