Most corn planting happened two to four weeks later than normal thanks to April rains and below-average temperatures. Despite the later spring, corn silage harvest is just around the corner, and for a few in outlying areas, it has already begun. A few strategies can help determine when to hit the fields and how to put up the highest quality forage possible.
Temperature affects crop growth and development. Accumulation of heat during the growing season can be used as a predictor of a plant’s developmental progress. Growing degree days is a calculation to express this heat accumulation. For the 2022 growing season, we gained significant GDD and were ahead of our historic averages for June and July. That trend has slowed recently with more moderate temperatures and added precipitation. This may keep harvest dates closer to normal despite delayed planting.
Note tasseling dates of fields. Silage harvest usually begins 42 to 47 days after tasseling. However, this is dependent on several factors, such as rainfall, temperature, corn hybrid and fertility. As harvest nears, monitor whole-plant moisture for a more accurate harvest date. Collect some representative stalks (manually or mechanically) and dry them or use near-infrared technology to obtain a whole-plant dry matter. The in-field dry down rate is typically 0.5 to 1 percentage point per day.
Identifying and achieving harvest goals has huge production and performance implications along with economic impacts. Corn silage must be ensiled at optimum DM to maximize packing density and fermentation. For bunkers and piles, the optimal DM range is 30%-35%. Bags are similar but may tolerate a couple points drier. Upright silos may need to be closer to 35%-45% DM depending on the exact structure.   
Corn silage kernel processing is critical, especially as DM and milk line progress. Pre-harvest is a good time to check processing roll condition and gap setting. Roll gap clearances are generally measured in millimeters with a normal opening of 1-4 mm.  This setting is dependent on kernel maturity, hardness and size. Settings ideal for harvest in previous years may be significantly different for the current crop.  
Once the chopper is rolling, evaluate kernel processing and adjust accordingly. The first method is to fill a 32-ounce cup with corn silage before ensiling. Spread it on a flat surface. You should see no whole or undamaged kernels. The second option it to use a bucket of water. Place a couple handfuls of corn silage in the bucket, skim off the floating plant material, pour off the water and evaluate the corn particles that remain in the bucket.  
Theoretical length of cut determinations for corn silage are dependent on factors such as harvest DM, percentage of ration contribution and storage structure. Typical TLOC ranges from five-eighths to 1 inch (16 to 25 mm). As DM increases, considerations need to be made to shorten the TLOC.  
 Finally, be safe. Corn silage harvest brings increased machinery traffic and long hours. Fermentation results in the production of potentially deadly gases that can accumulate in the silo and unloading area. Exercise caution in these areas. As always, make safety your top goal this corn silage season.