Interaction between soil and fertiliser nitrogen drives plant nitrogen uptake and nitrous oxide (N2O) emissions in tropical sugarcane systems

Abstract

Abstract Aims High nitrogen (N) fertiliser inputs in intensive sugarcane systems drive productivity but also significant emissions of nitrous oxide (N2O), a potent greenhouse gas. Fertiliser and soil N availability for both plant N uptake and N2O emissions across different N rates remain unknown, hindering efficient N management. This study investigated the contribution of fertiliser and soil N and their interaction to plant N uptake and N2O emissions in two intensively managed tropical sugarcane systems. Methods High temporal resolution N2O measurements were combined with 15N recoveries across four N fertiliser rates, (100, 150, 200 and 250 kg N ha− 1) in soil, plant and N2O emissions. Results Cumulative N2O emissions ranged from 0.3 to 4.1 kg N ha− 1, corresponding to emission factors ranging from 0.7 to 2.4%. Native soil N accounted for > 60% of cumulative N2O emissions and total plant N uptake. Fertiliser N addition increased N2O emissions from native soil N compared to the unfertilised control, highlighting the interaction between fertiliser and soil N, which determined the overall magnitude but also the response of total N2O emissions to N rates dependent on the site conditions. Overall fertiliser 15N loss responded exponentially to N rates with 50% of applied N fertiliser permanently lost even at the recommended N rate. Conclusions The interaction between fertiliser and soil N and its contribution to N uptake and N2O emissions demonstrate the importance of integrating soil fertility management with N fertiliser rate recommendations for sugarcane systems to maintain crop productivity and reduce environmental impacts.