NATURE AND MAGNITUDE OF SOIL-EROSION IN SUGARCANE LAND ON THE WET TROPICAL COAST OF NORTH-EASTERN QUEENSLAND

This paper reports measures of soil erosion in sloping sugarcane land under conventional cultivation and various no-tillage surface manageme nt techniques and explores the reasons for the differences measured. S oil erosion from conventionally cultivated ratoon cane lands was measu red in the range 47-505 t/ha.year, with an average annual loss of 148 t/ha.year. No-tillage practices reduced this erosion to <15 t/ha.year. Groundcover did not affect soil erosion significantly. In the absence of hydrological data, it is anticipated that consolidation of the soi l surface at harvest, rather than ground surface cover, is the dominan t factor reducing soil erosion. The effect of groundcover on soil eros ion is less than the accuracy of the measurement techniques employed ( +/- 20 t/ha.year). Physical and chemical analyses of in situ and erode d soil indicate that sediment from the no-tillage practice may be tran sported further from the erosion site and carry a more mobile fraction of nutrients.