Strategies to mitigate the nitrous oxide emissions from nitrogen fertilizer applied with organic fertilizers in sugarcane

Abstract Vinasseis a major byproduct of the sugarcane biofuel industry, recycled in the fields. However, there is evidence that the application of vinassewith mineral nitrogen (N) fertilizers in sugarcane enhances the emission of greenhouse gases (GHGs). Therefore, strategies are needed to decrease the environmental impacts caused by both inputs. We carried out three sugarcane field experiments by applying N fertilizer ( ammonium nitrate) with types of vinasses(concentrated-CV and standard-V) in different combinations ( vinasseswith N fertilizer and vinassesone month before or after mineral N fertilization). The gases nitrous oxide (N 2 O), carbon dioxide (CO 2 ) , and methane (CH 4 ) were measured in one experiment fertilized in the beginning (fall/winter = dry season) and two experiments fertilized in the end (spring = rainy season) of the harvest season. Sugarcane fields were sinks rather than sources of CH 4 , while total carbon emitted as CO 2 was similar between seasons and treatments. The effect of mineral fertilization and vinasses(CV and V) on N 2 O emissions was highly dependent on soil moisture (rain events). The N 2 O-N fertilizer emission factor (EF) varied from 0.07% to 0.51%, whereas the average EF of V and CV were 0.66% and 0.34%, respectively. On average across the three experiments, the combination of vinasse(CV or V) with N fertilizer increased the N 2 O emissions 2.9-fold compared to that of N fertilizer alone. For CV + N, the EF was 0.94% of the applied N and 0.23% of the ammonium nitrate-N, and for V + N (EF = 0.47%), increased emissions were observed in two out of three experiments. The strategy of anticipating or postponing vinasseapplication by one month with respect to mineral N reduced the N 2 O emissions by 51% for CV, but not for V. Therefore, to avoid boosting N 2 O emissions, we suggest applying vinasses(CV and V) before or after mineral N fertilization.