Uptake of water from a Kandosol subsoil: I. Determination of soil water diffusivity
To determine soil water diffusivity, D(θ), 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.
The method is based on the analysis of one-step outflow induced by a turbulent stream of dry air over the exposed end of a soil core, with the other end of 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(θ) is calculated by deconvoluting the measured outflow function.
Over the suction range of 10 to 150 m of water, D(θ) calculated on the undisturbed soil ranged from 20 × 10−9 to 10 × 10−9 [m2 s−1], substantially higher than other published estimates over this range in suction.
These unusually large values cast doubt on the view that flow of water to roots limits uptake of water from the targeted subsoil.
KeywordsRoot water uptake Plant water uptake Undisturbed soil Outflow Evaporation Numerical analysis One-dimensional flow equation
DD received a PhD scholarship from the Cooperative Research Centre for Irrigation Futures and a PhD top-up from the CSIRO Water for Healthy Country flagship. This manuscript was written while DD received a writing up award from Charles Sturt University.
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