Harvesting
Physiological maturity (black layering) occurs when the grain moisture content reaches 31%–33% moisture. After this stage, there is no dry matter added to the corn kernel. Harvesting grain corn at moisture contents above 28% often results in significant damage to the grain and makes it more difficult to market commercially. High quality food grade markets may require harvest moistures to be as low as 20%–22%.
Weigh the benefits of delaying harvests (e.g., lower drying costs and improved sample quality) against the increased risks (e.g., higher levels of stalk lodging, ear drop and wet weather). Scout fields and check for stalk quality to determine the need to adjust harvesting dates forward to prevent harvest losses. When stalk quality is poor, the next significant wind or rainstorm may increase harvest losses dramatically. Efficient header performance is also important when harvesting corn with poor stalk strength. Keep header speed in step with ground speed to improve stalk flow down through the stripper plates and snapping rolls. If necessary, adjust them closer together.
Damage by the combine to grain quality can result from any of the following:
- cylinder speed too high
- concave clearance too narrow
- too many concave filler bars
- concave and cylinder not parallel
When harvesting corn that has been frozen prior to maturity, experience indicates that running the cylinder speed as slow as possible is the key to maintaining quality.
Use these guidelines to assess combine harvest losses:
- 22 kernels per square metre (2 kernels/ ft2) represents approximately 0.06 t/ha (1 bu/acre) loss
- one average-sized ear in 1/100 acre (6.4 m2 or21 ft2) represents 0.06 t/ha (1 bu/acre) in lost yield
If combine losses exceed 0.16 t/ha (2.5 bu/acre), make adjustments.
Harvesting and Storing Corn Silage
See Haylage and Corn Silage in the Harvest and Storage section of Chapter 3, Forages.