Untersuchungen zum Bodenlufthaushalt in einem Bodenbearbeitungsversuch. 2. Gasdiffusionskoeffizienten als Strukturmaße für Böden

Investigation of the soil gas regime in a tillage experiment: 2. Apparent diffusion coefficients as a measure of soil structure In a soil tillage experiment with nursery stock on three different soils the apparent diffusion coefficients for CO₂ were measured using soil cores of different depths at different times. Not-tilled, herbicide treated plots were compared with rototilled plots. The relationship between the relative apparent diffusion coefficient and the air content may be described by an exponential regression function D_s/D_a = 0.0085 · e^6.8E_L, if all measurements are taken into the calculation. By dividing into different soil textures different regressions are obtained for the three studied soils: a sand, a silt and a clay loam. In many cases it is possible to show by the changing D_s(E_L) regression changes of the soil structure with depth or as a result of tillage. In all these cases the soil of the not tilled plots turns out to be better structurized than that of the tilled ones, demonstrated by higher D_s-values at equal E_L. The interpretation of the differences is being tried with the aid of soil pore tortuousity and continuity. Finally the measured D_s(E_L) relationships are applied to characterize the soil gas regime for two seasons, using CO₂ concentration profiles of the soil air on a day in summer and fall, respectively. It is shown, that CO₂ production reaches farther down in summer than in fall.