Corn silage harvest has already begun in some areas of Lower Michigan, especially in dry spots with lighter soils. The 2013 growing season in Michigan has been anything but typical. Spring and summer were both wet and cool and hot and dry. Across the state, there are good corn crops, average corn crops and poor corn crops. No matter what the crop looks like, one thing is the same – Michigan State University Extension recommends that corn silage should be harvested between 60-70 percent moisture and 30-40 percent dry matter (DM).

Whole-plant dry matter is the best predictor of when to harvest, not kernel milk line. Digestibility of neutral detergent fiber (NDF) and starch are more closely linked with whole-plant moisture than with kernel milk line. Whole plant dry matter between 30-35 percent indicates the digestibility of NDF and starch is optimal.

It is important to harvest when NDF digestibility is high because a one percentage unit increase in NDF digestibility is associated with an increase of 0.55 pounds of 4 percent fat corrected milk. Delaying corn silage harvest resulting in a 10 percent drop in NDF digestibility could result in a loss of 5.5 pounds of milk per cow for the whole year while essentially having the same expenses incurred with planting, harvesting and packing.

Storage type will determine which moisture level will result in optimal fermentation. See Table 1 for moisture/dry matter goals by storage type. If silage is harvested too wet, fermentation will be dominated by undesirable clostridial fermentation which may result in poor animal intake and performance.

Silage put up too wet will also seep, leaching valuable nutrients into the environment. Silage run off should be contained and diverted to containment or funneled through a filter strip of growing vegetation. If silage is harvested too dry, there might not be enough sugars present for adequate fermentation, starch digestibility will be lower, silage will be difficult to pack, too much oxygen will be present and may result in silage that has heated and molded.

Table 1: Moisture goals by storage type

Storage type

Moisture Goal

Dry Matter Goal

Horizontal bunker

70-65 percent

30-35 percent

Silo bag

70-60 percent

30-40 percent

Upright silo

65-60 percent

35-40 percent

Whole plant dry matter can be measured by using a Koster™ Moisture Tester or a microwave oven. In addition, many local feed companies offer events where producers can bring in whole plant samples for a dry down.

Corn silage put up in the fall will feed the animals for the whole year. Make sure that every step is taken to put it up right.