The effect of crop type, crop rotation, and tillage practice on runoff and soil loss on a Vertisol in central Queensland

Abstract

In 1982, a long-term project was established in central Queensland to study the effect of crop type, crop rotation, and tillage practice on runoff and soil loss. Runoff and soil loss were measured at the outlet of 9 large contour bay catchments (approximately 13 ha) where wheat, sorghum, and sunflower were grown in 3 crop sequences. Each crop sequence consisted of zero, reduced, and conventional tillage fallow practices. Monoculture cropping was practised from 1983 to 1985, then opportunity cropping from 1986 to 1993. During the study, wheat cropping had lower average annual runoff and soil loss (P < 0·01) than sorghum and sunflower. Zero and reduced tillage retained more crop stubble (median >50%) and had less soil loss (P < 0·05) than conventional tillage. Zero tillage wheat had the lowest average annual runoff and soil loss, and conventional sunflowers had the highest. The erosion risk associated with sunflowers was reduced by a wheat–sunflower crop rotation, particularly when zero-tilled. Monoculture sunflower must be avoided. The region is susceptible to large episodic erosion when crops are not sown, there are long fallows, and soil cover falls below levels critical to control erosion (<30%). Opportunity cropping is the most appropriate system to maximise the regions variable rainfall and reduce runoff and soil loss.