Abstract
The permeability of silage is of great significance in aerobic deterioration. Relationships have been determined between permeability, porosity, dry matter content and density. Porosity is theoretically linearly related to density and this was confirmed experimentally. Permeability is theoretically directly related to porosity and hence to density for single phase fluids in solid matrices. The presence of moisture in silage, however, reduced permeability so that permeability (κ) was dependent on both density (ρ) and dry matter (D) according to the equation: κ = 726 - 0·368D - 0·737ρ - 94·0 D/ρ, where permeability is in μm 2, dry matter is in g/kg and ρ is in kg/m 3. The combination of this equation with a model that predicts silage density gradients allows vertical gradients of permeability to be predicted. In a 6 m diameter silo containing silage of initial density 400 kg/m 3 and dry matter content of 240 g/kg, the permeability would range between 280 μm 2 at the top to 2 μm 2 at the bottom. The significance of these results for the mathematical modelling of aerobic deterioration is discussed.
Published Version
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