Nitrogen Losses, Trade-Offs, and Mitigation Potential in Global Sugarcane Cropping Systems

Abstract

Excessive nitrogen (N) inputs in warm and wet sugarcane cropping systems lead to substantial ammonia (NH₃) volatilization, nitrous oxide (N₂O) emission, nitrate (NO₃⁻) leaching, and dissolved inorganic N (DIN) runoff, posing risks to air quality, aquatic ecosystems, and climate forcing. A global, integrative understanding of the drivers of these loss pathways and the effectiveness of management practices is required to balance sugarcane productivity with reductions in environmental N pollution across diverse sugarcane regions. Here we synthesized data from global sugarcane experiments to derive region-specific emission factors (EFs) for multiple N loss pathways and to identify key biophysical and management controls on N losses, crop yield, and their trade-offs. Brazil showed the highest NH₃ volatilization EF (7.4%); Australia the highest N₂O emission EF (2.6%); and Brazil the highest NO₃⁻ leaching EF (8.9%), highlighting strong regional contrasts in N loss dynamics. Across regions, N application rate and cane trash retention were major regulators of NH₃ volatilization, with surface trash retention overriding soil pH and clay effects. N₂O emissions increased with high N inputs and carbon availability, but were negatively associated with water inputs, suggesting enhanced complete denitrification under wetter conditions. High N and water inputs increased DIN runoff. Increasing N input enhanced sugarcane yield but also amplified all major N loss pathways. Cane trash retention increased yield but raised NH₃ and N₂O losses, whereas adding carbon-rich sugar mill by-products reduced NH₃ but increased N₂O emissions. Urease and nitrification inhibitors effectively reduced NH₃ and N₂O losses, respectively, while controlled-release fertilizers showed inconsistent impacts. Scenario-based modelling demonstrates trade-offs between N loss reduction and productivity, with urease and nitrification inhibitors substantially reducing N losses without compromising yield, outperforming strategies based solely on N rate reduction or cane trash removal. These findings together inform sustainable N management strategies that mitigate environmental impacts while maintaining sugarcane productivity.