Corn silage harvest moisture and management

Farm Forum

Corn for silage should typically be harvested between 60-70% moisture. This moisture range is the most ideal for optimum fermentation and a rapid drop in pH to preserve the feed value of the crop.

Some tips that will help the harvest process and quality of the silage are:

1. Keep a close eye on corn maturity once it has dented. Corn can rapidly mature or dry down due to weather and moisture conditions.

2. A very basic estimate of whole plant moisture for harvest can be made using the kernel milk line. The kernel milk line is the dividing line between sugars in the maturing kernel and starch deposited. Most producers in South Dakota will use the 1/3 milk line as the point to start checking whole plant moisture to determine the optimum timing for silage harvest. On the other hand, maximizing the nutritional quality of corn silage and minimizing shrink losses are two main factors to take into consideration when feeding livestock. Therefore, harvesting corn silage too early at less than 30% dry matter (DM) will result in lower starch concentration in the silage. However, mature corn silage (silage with more than 38% DM) could also have less nutritional value because of lower fiber and starch digestibility.

Moisture content can be estimated in chopped silage using the “grab test method” as shown in Table 1. Other testing procedures that that involve drying and weighing the samples will yield more precise results.

3. If you have immature corn to harvest, allow the crop to mature as long as possible to increase dry matter yield per acre.

4. Adding a research proven bacterial inoculant to corn silage can reduce dry matter losses and increase silage digestibility.

Factors Affecting Shrink Losses

1. Type of structure: bunkers usually have greater shrink compared to other types of storage structures.

2. Chop length: finely chopped forages can be packed more effectively, however chopping too finely can result in not enough effective fiber in the diet. Cutting lengths of approximately ½ to as much as ¾ range because of effective fiber should be satisfactory. Making sure that the knives are sharp also will improve the pack density.

3. Rate of filling: slow filling will reduce the rate of fermentation so that pH stays higher for longer time. Some of the problems with shrink losses are the air trapped inside the silage. This will promote yeasts and mold causing serious problems to the final product.

4. Packing capacity: Not having enough packing equipment at the pile to keep up with the capacity of today’s silage choppers can be a challenge. Adding a second tractor may be called for to make sure that the silage can be packed thoroughly.

5. Covering the silage: covering a bunker with plastic as soon as possible after filling is the best choice to reduce shrink and spoilage losses.


Stored silage can provide high quality forage needed to support livestock systems. Pay attention to maturity stage, and leaf/stem ratio. Maximize nutritional value of corn silage by chopping corn when is between 30-38% DM. Shrink losses are usually minimized by chopping fine enough, filling rapidly, packing, and an adequate and fast sealing with an air-tight cover.