By Jeff Burbrink
Extension Educator, Purdue Extension Elkhart County

September was always one of my favorite times as a kid. It was exciting because I loved helping make silage. The hustle and bustle of the tractors and wagons and chopper, the smell of fresh chopped corn stalks; all of it signaled the start of harvest for me.

Corn silage is our number one feed in tonnage fed to local dairy cattle. Making good corn silage generally means having a good base to make good quality milk.

The moisture content of silage at harvest is very important. Too high, and nutrients run out the bottom of the silo in a sticky smelly soup, which can also damage the silo and contaminate water supplies. Too low, and the fermentation process stalls, decreasing digestibility and increasing mold and spoilage due to trapped air.

Ideally, corn silage should be harvested at the moisture content appropriate for the type of silo used. Recommended moisture contents are 65–70 percent for horizontal silos, 63–68 percent for conventional tower silos, 55-60 percent for limited-oxygen silos, and 65 percent for silo bags.

Silage moisture at harvest is not difficult to determine and should be monitored, if possible, to prevent harvesting of the crop outside of the desired moisture range. A commercial forage moisture tester or a microwave oven and scales can be used to determine the moisture content fairly rapidly. If silage moisture is above ideal levels, then harvest should be delayed if possible.

One strategy for timing corn silage harvest is to chop a sample at the full dent stage, just as the milkline appears, and determine the moisture content. Then estimate the harvest date by using a typical dry down rate of .50 to .75 percentage units per day.

The size of the chopped particles makes a difference in the fermentation process. Most of the research suggests the length of the cut should average three-eighths to three-fourths inch. This should be monitored throughout silo filling because the particle size can vary as the crop moisture content changes.

Once harvesting has begun, fill the silo as rapidly as possible and continue until it’s filled. Kernels of corn should be broken into pieces and cobs broken into thumbnail sized or less pieces. Once the kernels are past the half milk-line stage, it may be good to have more kernel breakage to increase digestibility.

In bunker silos, packing the silage is important to limit the amount of air in the pile. Many people use a technique called progressive wedge packing, where the silage is packed continually at a 30 to 40 percent grade. Another technique is to spread layers of silage in thin layers, maybe six to eight inches deep, and pack it by driving over the pile. Either way, the density after packing should be around 14 pounds of silage (dry matter) per cubic foot.

One final thought is safety. The equipment used to chop silage can also damage people, and very quickly. Keep safety in mind as you are working the fields and filling the silos. It is easy to get in a hurry and forget that the whole reason you are doing this is to benefit your family. Be especially mindful of the children, who are drawn to the equipment like flies to honey.

Be sure to open windows and doors in areas where silo gasses can accumulate. These gasses are silent killers of both people and livestock. It is best to keep family members and employees away from these areas when the silage is fermenting.