Uptake of water from a Kandosol subsoil: I. Determination of soil water diffusivity

Aims: To determine soil water diffusivity, D('), on undisturbed field soil at medium to low water content (suction range from 10 to 150 m of water), for the purpose of modeling the uptake of water by plant roots.Methods: The method is based on the analysis of onestep outflow induced by a turbulent stream of dry air over the exposed end of a soil core, with the other endof the core enclosed. The outflow is measured through time as the change in the weight of the core as it sits on a recording balance. D(') is calculated by deconvolutingthe measured outflow function.Results: Over the suction range of 10 to 150 m of water, D(') calculated on the undisturbed soil ranged from 20×10'9 to 10×10'9 [m2s'1], substantially higher than other published estimates over this range in suction.