Quantification of the effects of zero and mechanical tillage on a vertisol by using shrinkage curve indexes

The effect of zero versus mechanical tillage on the structure of the top 0.1 m of a Vertisol at Hermitage, near Warwick, Queensland, was examined by using indices derived from fitting three straight lines to soil shrinkage data. The data were generated from the slow drying of initially, near-saturated, SARAN-coated soil clods. Values of specific volume and the specific volume of air-filled pores were significantly greater in the mechanically tilled rather than the zero-tilled soil, showing that mechanical tillage has led to decreased bulk density and increased porosity in the surface layer of this soil.