It’s that time of year already, when silage is on many minds. Let’s objectively review some best practices for accurately determining the time for harvesting corn for silage. Corn whole plant moisture is key for proper fermentation and is often the most difficult criteria to determine. Harvesting too wet results in reduced yield, souring, and seepage, while cutting too dry also reduces yield, causes molding, and lowers digestibility and some nutrients.
The first step to successful moisture determination is to decide field harvest order and initial plant sampling. This can be accomplished by keeping field notes of the order that you planted your fields. In your records, if you jot down corn silking dates, you will be able to project the number of calendar days needed for that field to reach maturity. Corn typically reaches maturity (R6 or ‘black layer’) about 55 to 60 days after silking. Noting when your field’s silk assists with planning for harvest and scheduling chopping; silage harvest typically starts about 42 to 47 days after silking or when corn has reached the 50% kernel milk stage.
In addition to monitoring when the corn plant silks, the other indicator to help establish field harvest order is kernel milkline movement. Monitor moisture of silage fields when you observe milkline movement and base the sampling date on moisture ‘triggers’ based on the storage structure. For more detailed information on kernel milk stage ‘triggers’ for timing silage harvest, please refer to Sampling Corn Silage Fields to Accurately Determine Moisture, by Dr. Joe Lauer available at: http://fyi.uwex.edu/forage/sampling-corn-silage-fields-to-accurately-determine-moisture/.
Here are some tips for accurately determining whole plant moisture in fields that do not develop uniformly. Hypothetically, divide the field into sections that represent your corn plant’s stage of development (i.e. development on high spots vs. low spots). Then when sampling, collect 3 to 5 plants, in a row, from at least two or more different representative locations within each field section. For example, if you divided your field into two representative locations, such as corn growing on high spots in your field and that grown on the lower spots, you would collect two samples (3 to 5 plants in a row) for a total 6 to 10 total plants from the high areas and two samples for a total of 6 to 10 plants from the low areas. Repeat sampling the same field locations to determine drydown rate over time. Research by Scott Hendrickson shows drydown varies by the year, but typically ranges from 0.4 to 0.7 percent per day.