Relationship between hydraulic and basic properties for irrigated soils in southeast Australia

This paper examines the potential of soil maps and spatial information on basic soil properties for predicting soil hydraulic properties in the Shepparton irrigation region (SE Australia). For this purpose, the relationship between locally measured soil hydraulic properties and basic soil properties, and soil categories was analyzed. Pedotransfer functions developed for Australian soil were tested. Furthermore, association of field-scale final infiltration rates with basic soil properties was investigated. Water-retention properties, and in particular subsoil water-retention properties, were significantly correlated with readily available basic soil properties. Spearman's rank correlation coefficients were particularly high for clay content, bulk density, and the sum of exchangeable cations Ca2+, Mg2+, Na+, and K+. Water-retention properties were adequately predicted using Australian pedotransfer functions. Water-transmission properties such the saturated conductivity and the final infiltration rate were overall poorly correlated with basic physical and chemical properties. Generally, median water-transmission properties did not significantly change with soil groups and “within-paddock variability” accounted for over half of the “within-soil-type variability” for many soil types. We concluded that it is feasible to regionalize water-retention properties for the Shepparton irrigation region using basic physical and chemical soil properties, whereas the information on basic soil properties and from soil maps was insufficient to reliably estimate water-transmission properties. It is demonstrated why field-scale estimates of final infiltration rates, obtained by fitting a model for surface irrigation to field measurements of advance, depletion, and recession, may be better correlated with basic soil properties.