Agronomists note that a rough estimate of the proper silage harvest period is somewhere between 35 and 45 days after tassel emergence.

In many areas of south-central Pennsylvania, tasseling began close to July 11 on the earliest planted corn. This would indicate that silage harvest should begin close to the 3rd week of August, but in many drought areas silage harvest has begun already.

No one can accurately predict the exact date based on tasseling due to many factors including weather conditions, hybrid characteristics and storage structure type.

Harvest moisture timing

Depending on storage structure type, corn silage is harvested when whole plant dry matter reaches 30 to 35 percent. Optimum dry matter content for bunker silos is 33 to 35 percent; ag bags — 33 to 37 percent, conventional upright silos — 35 to 38 percent and oxygen-limiting silos — 40 to 45 percent dry matter.

Proper moisture at harvest is critical and there is a wide variation in the actual moisture of the crop based simply on the milk layer.

The most accurate measurement of whole plant moisture is to conduct moisture testing. Begin by taking a few plants from selected fields at dent stage. Run these plants through some type of chopper or lawn mower and thoroughly mix together.

Use a Koster tester or a microwave to determine whole plant moisture.

This moisture can then be used to predict harvest date. The expected dry down rate for corn silage is 0.5 to 0.6 percent per day. For example, if your crop moisture levels test at 70 percent and your target harvest moisture is 65 percent you need an additional dry down of 5 percent.