Determining when to harvest corn for silage

The old "stand-by" method when it came time to determine whether corn had dried down enough to be harvested for silage was to look at the milk line on a few ears in a field and make a determination that way.  However, due to hybrid variations and various other factors, this method is no longer a good predictor of the corn crop's overall dry matter percentage.  Instead a better way to determine the crop's dry matter percentage is to actually pull some samples, dry them down and see just what exactly the dry matter percentage is.  Methods to do this are below and are taken from a recent article of the Crop Observation and Recommendation Network (CORN) Newsletter published by Ohio State University Extension professionals.


"How to Sample Fields
Collect about 5 representative plants from the entire field, from areas with representative plant population and not from edge rows. Collect separate samples from areas that may have different dry down rates, such as swales, 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.

As soon as the plants are collected, chop them uniformly (using a cleaver, machete, chipper shredder, or silage chopper) and mix thoroughly to obtain a sample with representative grain to stover ratios for dry matter determination. Put representative sample in a plastic bag and keep it cool (refrigerate if possible). 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, a vortex dryer, or taking to a lab. For more details on these and other methods, see the following links:
http://www.extension.org/pages/Dry_Matter_Determination
http://ohioline.osu.edu/agf-fact/0004.html
http://abe.psu.edu/vortex-dryer

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 is largely affected 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.

From our work, on-farm measurement of dry matter is probably only accurate to +/- 2 units. So if you measure a DM of 30% it could easily be 28-32%. Keep this in mind as you plan harvest timing.”

The selection above is only a piece of the entire article.  To read the rest, go to http://corn.osu.edu/c.o.r.n.-newsletter#3.