IMPACT OF TRASH BLANKETING ON SOIL NITROGEN FERTILITY: AUSTRALIAN AND SOUTH AFRICAN EXPERIENCE

摘要

Trash blankets contain substantial amounts of nitrogen (N) and other nutrients. The availability of N in trash is complicated because most of the N cycles through the soil organic matter. To gain insights into the long-term fate of N contained in trash, N balances were analysed in two trash management experiments, in Australia and South Africa. Long-term N balances were simulated with the APSIM-Sugarcane cropping systems model that was verified against cane yields and soil C data measured in the experiments. In a 35 years simulation of the Australian experiment, the model suggests that 86% of the N in the trash blanket, which otherwise would have been lost by burning trash, was either 'stored' in the soil organic matter or exported from the site inharvested cane. In simulations of the South African experiment, trash blanketing reduced the rate of organic matter depletion and maintained N exported in cane at levels similar to that in the burnt treatments, which had higher inputs of N from fertiliser. The study illustrates the positive effect of long-term trash blanketing on N cycling (particularly soil organic N) in sugarcane systems and the pivotal role cropping systems modelling can play in assessing the fate of N originating from trash blanketsin response to different soils, climates and managements.