Field measurement and estimation of soil water and chemical transport in deep sands

Yvette Oliver

    Research output: ThesisDoctoral Thesis

    27 Downloads (Pure)


    [Truncated] Acidification caused by nitrate leaching is becoming an increasing concern in agricultural systems, particularly on deep sandy soils. To predict acidification in deep sands, the key question is whether changes to the cation-anion balance can be adequately modelled and monitored through time. In this study, a mechanistic modelling approach was used to investigate the transport of cations and nitrate under transient water flow conditions. Unsaturated flow was modelled using the Richards Equation and combined with the convection-dispersion equation (CDE) including cation selectivity terms to describe cation transport. The possibility of preferential flow was investigated by comparing output from the CDE with a modified form of the CDE referred to as the immobile-mobile model (MIM).

    A particular focus of this study was physical and chemical parameter measurement and estimation for water flow, solute transport and cation transport models. Laboratory measurements were performed on intact and repacked columns. Field measurements were performed in situ on deep ripped and unripped tillage treatments. A number of existing analytical hydraulic equations, as well as equations based on indirect relations for Australian soil, were compared. The subsequent effect of the different hydraulic equations, measurement techniques and farming treatment on the predicted water balance were compared with field measured data obtained by automated time domain reflectometry (TDR).
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    • The University of Western Australia
    Publication statusUnpublished - 2002

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