Most corn planting happened two to four weeks later than normal thanks to April’s blizzards and below-average temperatures. Despite the later spring, corn silage harvest is just around the corner and, for a few, it has already begun. A few strategies can help you 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 plant developmental progress. Growing degree days (GDD) is a calculation to express this heat accumulation. The GDD equation utilizes maximum and minimum daily air temperature to determine the average daily temperature and subtracts a base temperature of 50 degrees. Upper and lower limits of 50 to 86 degrees are used because corn growth rate is near zero at 50 degrees and growth rates do not increase above 86 degrees. For the 2018 growing season, we moved ahead of our historic average in early June and have remained a couple hundred degrees above for the season.
    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 to obtain a whole-plant DM. The rate of dry down is typically one-half to 1 percentage point per day.
    Identifying and achieving harvest goals has huge production and performance implications along with economic impacts on your dairy. Corn silage must be ensiled at optimum dry matter (DM) to maximize packing density and fermentation. For bunkers and piles, the optimal DM range is 30 to 35 percent. Bags are similar, but may tolerate a couple points drier.
    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 (mm) with a normal opening of 1 to 4 millimeters. 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 (TLOC) determinations for corn silage are dependent on factors such as harvest DM, percentage of ration contribution and storage structure. Typical TLOC ranges from 5/8 to 1 inch (16 to 25 millimeters). As DM increases, considerations need to be made to shorten the TLOC.
    Finally, be safe. Corn silage harvest brings an increase in machinery traffic and long hours. Fermentation results in the production of potentially deadly gases that can accumulate in the silo and unloading area. Use precaution in these areas. As always, make safety as your top goal this corn silage season.
    Barry Visser is a nutritionist for Vita Plus.