Good quality silage starts with good quality forage. Ensiling can only preserve nutrients and dry matter (DM) already present in the crop. When preparing to harvest corn for silage, there are three important characteristics and measurement techniques. While basic, every producer must master these critical steps in order to produce high-quality silage.  

1. Dry matter (DM)

Achieving the proper DM content for the specific forage at harvest is important for maximizing nutrient preservation and feed intake by the animal. Corn is optimally harvested for silage between 32 and 38 percent DM. High-moisture corn (HMC) is best harvested at 68 to 72 percent DM. Corn harvested at greater than 32 percent DM will benefit from using a kernel processor.

An easy way to test DM content is in a microwave oven. First, weigh out exactly 100 grams of fresh forage on a paper plate (adjust for the weight of the plate). Spread the forage evenly and place in a microwave oven. Heat on high for 4 minutes. Remove the silage, weigh and record. Heat the sample again on high for 1 minute. Weigh and record. Repeat this procedure until the weight remains the same.1

At this point, the weight in grams represents the DM content of the silage. To calculate the moisture content, subtract the dry matter content from 100.1

2. Maturity

To maximize quality, corn should be harvested for silage when the kernels are between one-half and two-thirds milk-line. Between these stages, starch content increases and fiber digestibility is in an optimum range. (See Figure 1.)

3. Chop length

A short chop helps packing and minimizes air infiltration into the silo, while a longer chop length increases effective fiber in the diet. Whole-plant corn that will be processed should be chopped at a theoretical length-of-cut (TLC) of 1/2 to 3/4 inches.

Actual chop length can be monitored in the field by using the NASCO® Penn State Forage Particle Separator. Ideally, after sieving the material should be distributed:

·         25-50 percent of particles less than 5/16 inch

·         40-50 percent of particles between 5/16 and 3/4 inch

·         10-25 percent of particles greater than 3/4 inch

Brushing up on the basics of these three important characteristics and techniques will help producers achieve the best forage possible — and create high-quality silages.

For silage management tips after harvest, visit or Ask the Silage Dr. on Twitter or Facebook.

1 University of Wisconsin Extension. Harvest and Storage. Accessed March 30, 2017. Available at: