Sugarcane production and soil physical decline

An unqualified but widely held view is that sugarcane production is deleterious for soil in general and soil physical condition in particular. In Australian sugarcane, though the area of land under production currently increases at approximately 4% a year, productivity (yield of sugar per harvested hectare) plateaued for the 20-year period from 1970 to 1990. To date, rationalisation of this 'yield decline' has focussed on changes with time-under-cane of soil chemistry, biology, microbial biomass and soil organic carbon status. In the current study, data collected on the same seven paired sites of the previous studies were: particle size distribution (PSD), bulk density (131)) and available water (AW) in three layers to 50 cm. PSD demonstrated that only one site varied significantly between old and new land. BD was significantly greater in the old land than new land at six of the seven sites in at least one sampled layer. Increases in BD ranged from 3% to 22%, the latter being a comparison between adjoining caneland and a forested area. Inter-rows had a greater BD than within row locations. Also, the magnitude of the increase in BD between row locations was greater than that between old and new land. Four sites demonstrated less AW in the old land than the new land; up to 20% less. The physical degradation of the old land agreed with sugarcane productivity decline measured at three of the sites at the time of soil sample collection.