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 CO 2 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 CO 2 concentration profiles of the soil air on a day in summer and fall, respectively. It is shown, that CO 2 production reaches farther down in summer than in fall.