Effects of Cultivar and Irrigated Water Quality on Sugarcane Residue Decomposition

In sugarcane cropping systems, green-cane harvesting has progressively replaced the traditional burning of standing crop prior to harvest, increasing the role of decomposition as a mechanism to replenish soil nutrients. We examined the impact of cultivar choice and irrigation water quality on decomposition of sugarcane residue. In two independent litterbag experiments, we isolated the effects of changes in plant residue quality and irrigated water quality. Cultivar residue exhibited significant variation of carbon and nitrogen concentrations and carbon to nitrogen ratio. Decomposition rate varied among cultivars, and those with greater carbon-to-nitrogen ratios decomposed faster than cultivars with lower ratios. Soil irrigated with river water showed a lower mineral and organic nitrogen concentration and decomposition rate than those irrigated with industry effluent wastewater. These results provide empirical evidence that both cultivar choice and water used for irrigation have a limited but significant impact on plant residue decomposition.