Do not combine fields. Greenchop may be sampled in multiple grab samples from the chopped material representing different sections of the field and representing different times of day. The principle is to fully characterize the range of DM in the entire lot being considered. There are methods of estimating DM using a microwave method which growers may use themselves, but these require a good microwave and a balance and a little time and attention. However, it is usually inexpensive to have a NFTA or California Recognized lab perform DM analyses at the same time that the forage quality is measured.
Dry matter can change very rapidly in a mass of forage.
Therefore, it's important to measure the forage as close to the 'point of sale' as possible. Different standards can be used for this second calculation, depending upon the purpose. In this case, the same calculation as above is used, but .30 is substituted for .9 in step 2.