Consequences of soil crust formation on soil hydraulic properties and irrigation performance

Rainfall and irrigation resulted in the formation of severe surface soil crusts. Crust formation resulted in significantly higher bulk density and significantly lower hydraulic conductivity including loss of nearly all macroporosity in the surface soil layers. Crust formation was accompanied by resettlement of the cultivated beds which also resulted in significantly higher bulk density and significantly lower unsaturated hydraulic conductivity. Crust formation and bed resettling prevented irrigation wetting up the crop seed bed, and increased the proportion of irrigation lost by runoff from 0.5 % to 35 %. Inverse simulation of cumulative tension infiltration data enabled the soil water characteristic of the surface crust to be determined and the effect of crust formation on infiltration modelled in HYDRUS 2D.