Sally Flis, Ph.D. – Feed and Crop Support Specialist
It is that time of the year again, corn is almost ready for chopping. Harvesting corn silage for the maximum quality and best fermentation requires monitoring and management.
The first factor to check is whole plant dry matter. Corn silage should be between 50 and 70 % moisture at chopping to provide for the best fermentation. This is dependent of the type of storage as outlined in Table 1.

Table 1. Recommended moisture for ensiling by storage type.

Storage StructureRecommended Moisture Content for Ensiling, %Kernel Milk Stage Trigger, %
Horizontal Bunk Silos70 to 6580
Bag Silos70 to 6080
Upright Concrete Silos65 to 6060
Upright Oxygen Limiting60 to 5040
University of Wisconsin – Agronomy Department, January, 1998, Joe Lauer

What is the best way to check and see if your silage moisture is correct for harvesting? A chopper equipped with a moisture monitor simplifies the process. Beware, however, dead leaves from N being drawn up through the plant or from disease can result in some deviation from the actual whole plant dry matter determined by a forage monitor.

Whole plant dry matter can be monitored by harvesting some corn silage from the field with your chopper and testing the moisture. Moisture of the plant can be determined by a Koster Tester, microwave, commercial lab or with new on farm NIR tools such as the NIR guns from Digistar or Chem Watch.

When using a Koster Tester or a microwave to determine moisture content of sample, be patient. If you do not let the sample on the Koster Tester go until there are no further changes in weight you may be under estimating your dry matter content. In a microwave, there are two things to be cautious of, 1) do not over heat the sample. Microwaving a sample for too long can cause it to catch on fire and then you have to start over and 2) as with the Koster Tester, make sure you have really reached a point where the weight of the sample is no longer changing.

More information on how to use a Koster Tester or microwave for dry matter determination is available in our newsletters.