Change in infiltration characteristics associated with cultivation history of soils in south-eastern Queensland

Change in soil infiltration characteristics with cultivation can result in reduced soil water storage, increased runoff and erosion, and reduced crop production. We measured changes in infiltration characteristics associated with years of cultivation for 5 soil groups in south-eastern Queensland. Soils were grouped according to soil type and texture into Sodosols, light and heavy Vertosols, Red Ferrosols, and Red Chromosols/Kandosols. Soil infiltration characteristics were determined from measurements of permeability and water-holding properties of the cultivated layer (0-0.1m deep) and the layer immediately below the plough layer (0.1-0.2 m deep). A rainfall simulator was used to measure the hydraulic conductivity of surface seals and infiltration of bare, tilled soil in the field. Hydraulic conductivity of the soil matrix and macropores and water-holding properties of the 0.1-0.2 m layer were measured with disc permeameters and pressure plate apparatus. Hydraulic conductivity of surface seals decreased exponentially in all soil groups with period of cultivation; half of the decline occurred within 2-6 years of first cultivation. Hydraulic conductivity, macroporosity, and moisture characteristic of the 0.1-0.2 m layer were similarly affected by longer periods of cultivation in all but light-textured soils. Cultivation of light-textured, hardsetting soils (18% clay) did not adversely affect hydraulic conductivity or macroporosity of the 0.1-0.2 m layer and the loosening effect of tillage was somewhat beneficial for the water-holding properties of this layer. The low hydraulic conductivities of the surface or 0.1-0.2 m layer after long periods of cultivation reduced infiltration of rainfall in the field.