Nutrient cycling, environmental outcomes and mitigation pathways in sugarcane agroecosystems: A comparative synthesis of Brazil and Australia

Sugarcane is a major tropical crop with strong potential to support climate-smart agriculture through efficient nutrient cycling, improved nitrogen use efficiency, biofuel production and enhanced soil carbon dynamics. However, environmental outcomes vary substantially across production systems. This review compares two leading high-efficiency sugarcane systems, Brazil and Australia, examining nutrient cycling, greenhouse gas emissions, nutrient losses and soil organic carbon storage. In Brazil, large-scale rainfed operations (commonly exceeding 10,000 ha) promote high organic inputs through residue retention and recycling of vinasse and filter cake, enhancing soil carbon stocks and internal nutrient recycling; however, these practices can elevate nitrogen losses and greenhouse gas emissions when poorly synchronised with crop demand. In Australia, smaller family-owned systems (~95 ha) operate under environmental regulations and the Six Easy Steps framework, where soil-test–based management, subsurface fertiliser placement and enhanced-efficiency fertilisers target nutrient transport to Great Barrier Reef catchments. Fertiliser-N use in Australian sugarcane has progressively declined to among the lowest rates globally for the crop; however, nitrogen use efficiency remains relatively low compared with Brazil, and off-site nutrient losses have not been fully resolved at scale. Soil compaction is a critical constraint in both countries, addressed by complementary strategies: satellite-guided controlled traffic farming in Australia and strategic subsoil tillage with GPS-guided traffic in Brazil. Across both systems, residue retention, legume rotations and reduced tillage improve nutrient cycling and soil carbon accumulation. Integrating Brazil's nutrient-recycling scale with Australia's precision management offers a convergent pathway to enhance nitrogen use efficiency, reduce environmental footprints and improve sugarcane agroecosystem sustainability.