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

Author: Deery David   Passioura John   Condon Jason   Katupitiya Asitha  

Publisher: Springer Publishing Company

ISSN: 0032-079X

Source: Plant and Soil, Vol.368, Iss.1-2, 2013-07, pp. : 483-492

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Abstract

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.