Crop residue removal and nitrification inhibitor application as strategies to mitigate N2O emissions in sugarcane fields

Highlights: • Straw preservation increases N₂O emissions and sugarcane yield. • Partial removal of straw decreases the intensity of greenhouse gas emission. • Nitrification inhibitor added to N fertilizer reduces the emission factor/intensity. • N₂O emissions were higher in the wet than in the dry season. • Nitrification inhibitor and partial straw removal effectively reduce N₂O emissions. Nitrous oxide (N₂O) emission estimates are important to ascertain the greenhouse gas balance of ethanol produced from sugarcane. We quantified N₂O emissions in the presence of sugarcane crop residues, N fertilizer (ammonium sulfate), and a nitrification inhibitor (NI, dicyandiamide). Two field experiments were conducted to evaluate the implications of N fertilizer application during dry and wet seasons at two locations in southeast Brazil. Treatments consisted of four levels of crop residue (0, 5, 10, and 15 Mg ha⁻¹) and three of N fertilizer (0 and 120 kg ha⁻¹ and 120 kg ha⁻¹ plus NI). N₂O emission was measured using the closed chamber method and sugarcane yield via mechanical harvest. N₂O emissions were higher in wet than in dry seasons following N fertilizer application, albeit affected by crop residue and NI in both. Retaining crop residues on the soil increased N₂O emission and sugarcane yield. The N₂O emission factor from N fertilizer ranged from 0.12% to 1.44% of N applied. NI reduced N₂O emissions (by 87% and 63% in dry and wet seasons, respectively). Sugarcane yield varied from 42 to 92 Mg ha⁻¹ of fresh matter stalk and emission intensity from 3.7 to 22.9 kg of CO_2eq. Mg of stalk⁻¹. The lowest greenhouse gas intensity was recorded with 5 Mg ha⁻¹ crop residue and 120 kg ha⁻¹ N supplemented with NI. Therefore, partial crop residue removal and NI addition to N fertilizer may be effective strategies to improve the sustainability index of biofuel from sugarcane and reduce N₂O emissions and intensity.