Effects of conservation tillage and rotation on water infiltration in two soils in south-eastern Australia

Abstract

The infiltration of water under long-term (8–10 years) conservation tillage (zero and subsurface tillage with stubble retention) and conventional tillage (frequent tined tillage with no surface residues) systems was compared on a grey cracking clay and a sandy loam soil in south-eastern Australia. Potential infiltration rates were higher under conservation tillage on both soil types. On the grey clay soil, stubble retention and zero tillage produced up to an 8-fold increase (from 12–33 to 145–206 mm/h) in saturated hydraulic conductivity (Ks) compared with the conventional practice of removing stubble by burning or grazing, followed by frequent tillage to control weeds. An annual application of nitrogen at 20–60 kg/ha had no significant effect on Ks. Similarly, on the sandy loam soil a 2-fold increase in Ks was observed from conservation tillage. Increases in Ks from approximately 46 to 96 mm/h occurred in rotations which included an 18-month fallow with conservation tillage (stubble retention and zero tillage) compared with conventional tillage (stubble removed and frequent tillage). A continuous rotation of pasture and wheat under conventional tillage had a significantly lower Ks of 22–23 mm/h which was increased to 47–49 mm/h with stubble retention and zero tillage. These differences in Ks explain an important mechanism for increased water storage on these soil types under reduced tillage.