Fig. 3. Test of air permeability models, Eq. [2] with = 2 and = 1 + 0.05b, against measured data for 12 undisturbed Andisols. Values of Campbell b and total porosity () are given for each soil. Soil macroporosity (₁₀₀) is marked for each soil. Measurements are mean of three closely spaced soil cores. Note that three different y-scales are used (60, 120, and 300 µm²).