Nitrogen losses in terrestrial hydrological pathways in sugarcane cropping systems of Australia

Abstract

The Australian Great Barrier Reef (GBR) is one of the world's best known natural ecosystems (Devlin and Schaffelke 2012). The catchments that drain into the GBR are best known for productive agricultural land that supports extensive grazing enterprises as well as croplands supporting sugarcane (Saccharum spp.), banana (Musa spp.), vegetables, cotton (Gossypium hirsutum L.), and grain industries. The sugar industry is based in closest proximity to the GBR lagoon, with sugarcane farms predominantly located in the coastal areas of these catchments. Sugarcane fields therefore have the potential to impact the quality of water entering the GBR lagoon through off farm movement of nutrients and pesticides, so careful management is warranted to limit any offsite impacts. Recent management practice changes in these coastal cropping systems have led to small but significant reductions in nutrient and sediment loads (Fabricius et al. 2014). Lower nitrogen (N) fertilizer rates have resulted in some reduction in offsite N movement (Webster et al. 2012), but the extent to which further N rate reductions are possible without having an impact on sugarcane productivity has yet to be explored. In this article, we discuss the impact of contrasting management systems on N losses in runoff from sugarcane farming