Nitrous oxide (N2O) emissions resulting from soil application of N fertilizers represents ~40% of the total greenhouse gas emissions from sugarcane ethanol production. Several studies have indicated that the contribution of N fertilizers to the total emission is considerably greater when associated with agroindustry residues, such as vinasse. Conversely, recent studies have indicated that the use of concentrated vinasse (CV) and the nitrification inhibitor (NI) addition have the potential to mitigate N2O emissions from sugarcane fields. Moreover, there are no studies about the efficiency of NI when used together with CV and N, or their direct impact on non-target N2O-producing processes in addition to the target process of nitrification. The aim of this study is to understand the effectiveness of NIs on the key microbial processes involved in the production and reduction of N2O in sugarcane soil following CV addition enriched with 15N-labelled ammonium nitrate (AN). Laboratory incubation will be conducted at the Agronomic Institute, Campinas-SP. Double and single 15N-labelling approach will enable quantification of the 15N-N2O produced from different microbial processes as well as quantification of 15N-N2 from denitrification. The CV application will be on the soil surface. All treatments with AN will be balanced to apply 120 kg N ha-1 at 50 atom % excess 15N. The NI will be the 3,4-dimethylyrazol-phosphate (DMPP) in a proportion of 1% of the applied N. The treatments will be: 1) Control (soil without N); 2) Concentrated vinasse (CV); 3) Ammonium nitrate (15NH4NO3); 4) NH415NO3; 5) 15NH415NO3; 6) 15NH4NO3 + CV; 7) NH415NO3 + CV; 8) 15NH415NO3 + CV; 9) 15NH4NO3 + CV + NI; 10) NH415NO3 + CV + NI; 11) 15NH415NO3 + CV + NI. The design will be totally randomised, with 4 replicates. This will be the first investigation of the CV enriched with mineral N effect on the respective contributions of different N2O-producing processes, as well as the influence of NI on these N2O sources. This information is particularly relevant, since understanding the contributions of the different processes to net N2O emission will help formulate management options for mitigation of this greenhouse gas, thereby promoting more sustainable production of sugarcane.
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