Determine silage density

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It is important to determine the density of the silage in your bunker. If silage is not packed densely enough, up to 20 percent of the silage can be lost. Brian Holmes, professor and extension agricultural engineer at the University of Wisconsin-Madison, says there are three different methods to determine silage density.

Silage density coring method. This method requires core samples be taken at the silage face to a depth of 12-inches at multiple sites. Samples should be weighed wet and then weighed after drying. The two weights can be used to calculate wet density and dry density. Average density is obtained by averaging the density of the several cored densities obtained at multiple sites around the feed out face.
Silage density calculator method. This method utilizes a spreadsheet from the University of Wisconsin Forage Extension Team Forage Web site. Values such as tractor weight, number of tractors, harvest rate, packing layer thickness, silage moisture content, wall height and peak height are entered by the end-user. The spreadsheet then calculates the average density.
Silage feed out method. Material should be weighed with a TMR mixer as it is removed from the bunker over a period of days. Divide the weight removed by the volume of material removed to receive your average density. To find out the volume, mark the location of the feed on day one. After feeding for several days, measure the distance the face has moved. Using a different spreadsheet from the University of Wisconsin Extension Team Forage Web site, enter face dimensions, weight of feed removed and calculate the average density.

A study at the University of Idaho found that the variation in density between storages was significantly higher for the feed out method than core sampling and calculator methods.

“Taking care to keep a vertical uniform face and weigh all loads with TMR scales will improve accuracy significantly over what was found at Idaho,” says Holmes.

The Idaho researchers recommend core sampling for directly assessing silage density and the calculator method for evaluating alternative management strategies during the filling and packing process. Holmes warns of the dangers of working close to the feed out face while core sampling. He recommends using the feed out method with precise measurement of a smooth vertical face and the area of that face as well as accurate weights of silage removed to safely estimate average density.

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