|Holmes, Brian - UNIV OF WISCONSIN MADISON|
Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 29, 2000
Publication Date: N/A
Interpretive Summary: Horizontal or bunker silos are an increasingly common way of storing forage for livestock. A key management factor to minimize losses and reduce storage costs is to attain a high density in the silo. However, the guidelines to attain high densities are based on relatively little research. The objective of this study was to determine those practices or factors most correlated with bunker silo density. Density was measured in 168 bunker silos across Wisconsin. Silo filling practices on those farms were surveyed and correlated with the measured densities. A large variation in density was found with the highest density being four times the lowest. Five factors were most strongly associated a high density: a heavy packing tractor, spreading the crop in thin layers, a tall silo, greater packing time per ton of wet crop, and a lower moisture content. These factors have been combined into an equation that will allow farmers to determine the best alternatives to improve silo density on their farms with their given resources.
Technical Abstract: High densities in bunker silos minimize losses and reduce storage costs; however, the guidelines to attain high densities are based on relatively little research. The objective of this study was to determine those practices or factors most correlated with bunker silo density. Density was measured in 168 bunker silos across Wisconsin using core samples collected at chest height across the feed out face. Silo filling practices were surveyed and correlated with density. Most silages sampled were alfalfa or corn. Dry matter densities ranged from 106 to 434 kg/m**3. The core densities were correlated with the height of silage above the core, indicating the effect of self-compaction. To adjust for this, all densities were corrected for the median depth below the surface (2.16 m) using equations for density with height for the center of tower silos. The adjusted dry matter densities were most strongly correlated with how thinly ya load was spread (L), tractor weight (W), packing time per tonne as fed (T) and dry matter content (D). These four factors were combined into a packing factor [W (TD)**1/2 L**-1] that explained 18.2% of the variation in dry matter density. Additional factors such as the use of dual wheels, etc. did not significantly improve the prediction of dry matter density. An equation was developed to predict average density in a bunker silo based on the packing factor plus crop height in the silo.