Comparison of the macropore structure of a sandy loam surface soil horizon subjected to two tillage treatments

Abstract. Erosion and excessive runoff from a crusting and hard-setting red-brown earth may he ameliorated with suitable management. A field trial, near Cowra, New South Wales, to assess the long-term effect of different tillage systems was used to compare the effect of direct drilling with conventional district cultivation practices under continuous wheat. The soil was sampled in the eighth year for assessment of the soil macropore structure, measurement of bulk density and hydraulic conductivity under tension. Vertical faces were prepared from resin impregnated blocks and the macropore structure described mathematically and visually using digital images and data generated from these images. Infiltration, bulk density and image analysis data all lead to the same conclusions about changes in pore structure. Under direct drilling no crust was evident, and there was greater macroporosity (> 0.175 mm diameter in section). The treatment effects appeared to be significant to about 30 to 35 mm depth at the time of sampling. Greater root and faunal activity were observed under direct drilling.