Preliminary on-farm data show that there can be a huge difference in corn silage density and dry matter loss between the top and bottom of a bunker.
In one bunker, silage at the bottom only had 4 percent to 5 percent dry matter loss compared to 10 percent in the top part of the structure, explains Ken Griswold, dairy extension educator with Penn State Cooperative Extension. Griswold, along with Paul Craig, extension agronomist with Penn State, buried silage samples in porous bags in various locations throughout the bunker during the 2008 harvest. At feedout, they re-weighed the samples to determine dry matter loss. They also took "core" density samples at the same locations. These measurements showed that silage in the top of the silo was 25 percent less dense than silage in the bottom half of the silo. The two factors together suggest that the less dense the silage is, the more dry matter loss you can expect to see.
During harvest, explain to your clients how important compression is during packing and how it influences silage density and dry matter loss. Griswold says a good recommendation is to aim for a minimum of 14 pounds of dry matter per cubic foot of silage during packing.