Fig. 7. Theoretical optimum water regime for aerobic microbial activity predicted from the Equation: = /ß = ² [( - _opt)/]^(2+3/b)/[1.1 _opt (_opt - 0.02 b)], and given as (a) the soil water content, , and (b) the water-filled pore space, WFPS. Solid lines indicate = 0.4 and broken lines = 0.6. Calculations were performed for three levels of the Skopp parameter, .