Farmers have benefited greatly from county and co-op corn silage drydown days. In some years, the economic impact of properly timing silage harvest is significant. If nothing else, better communication between farmers and custom silage choppers will help make both parties more successful.

How to Sample Fields

Collect 3 to 5 representative plants from the entire field. The plants should be representative from an area with representative plant population and not from edge rows. Collect separate samples from areas that may have different dry down rates, such as swales and knolls. The moisture concentrations of plants can vary within a field (plants will be wetter in low lying area and drier on knolls) and this should be considered when collecting your sample plants.

Put plants in a plastic bag, keep them cool, and chop as quickly as possible. The plants should be uniformly chopped (using a cleaver, machete, chipper shredder, or silage chopper) and then mixed thoroughly to obtain a sample with representative grain to stover ratios for dry matter determination. Some farmers prefer sampling only 2 or 3 plants without any additional sub-sampling to reduce the chances of a non-representative grain to stover ratio that can affect the results. In this case, choosing representative plants is even more critical.

Determine the dry matter content by drying the plant material using a Koster oven tester, microwave, convection oven, taking to a lab or using a vortex dryer. For more details on these and other methods, see the following links:

http://www.extension.org/pages/Dry_Matter_Determination (verified August 11, 2017)
http://extension.missouri.edu/p/G3151 (verified August 11, 2017)

Make sure the sample does not dry down and keep it cool until the dry matter determination is performed. The accuracy of the % dry matter value will be largely determined by the care taken in sampling, drying, and weighing the samples. Whole kernels and cob pieces can be difficult to dry completely without burning the leaf tissue.

Summary

To setup and manage a corn silage drydown day the following suggestions may be of use:

Objective: To assist farmers for timing corn silage harvest for their storage structures.

Schedule first "Drydown Day" date for when corn is at the R5 stage.
It is best if weekly Drydown Days are scheduled.
On every date, sample corn from the field at same site. Avoid border effects. This allows for tracking drydown rate of change from one date to the next.
If only one Drydown Day is scheduled, then use silage drydown rate of 0.5% per day from date of measurement.
Equipment: Brush chipper with self-sharpening blade (rather than hammer style)
Moisture determination method: NIR, Koster oven, microwave, oven
Arrange for people to help!

Results of county Drydown Days in Wisconsin can be found at http://fyi.uwex.edu/silagedrydown/ (verified August 11, 2017)