Straw preservation reduced total N 2 O emissions from a sugarcane field

• Published in: Soil use and management 2017-12, Vol.33 (4), p.583-594
• Main Authors: Pitombo, L. M., Cantarella, H., Packer, A. P. C., Ramos, N. P., do Carmo, J. B.
• Format: Article
• Language: English
• ISSN: 0266-0032; 1475-2743
• DOI: 10.1111/sum.12384

Post‐harvest biomass can be used as feedstock for energy production and alter N 2 O emissions from the soil, which is among the main issues determining bioethanol sustainability. To assess the effects of sugarcane straw return on gas emissions, we established a field experiment in which 0, 50, 75 or 100% (0, 5.65, 8.47 and 11.30 Mg/ha dry biomass, respectively) of the crop residues (straw) was left in the field during the first two ratoon crops. As fertilizer is applied in bands to sugarcane, we also investigated the contribution of different positions to the N 2 O emissions within the field. There was an interactive effect between straw and inorganic fertilizer, leading to a nonlinear effect of crop residues on the fertilizer emission factor ( EF ). However, straw consistently reduced N 2 O emissions from the field, acting mainly in the unfertilized areas in the field ( P  <   0.05). We observed that considering the typical EF used in the literature, the N 2 O‐N emissions attributed to fertilizer ranged from 0.19 to 0.79 kg/ha, while the total emissions ranged from 3.3 to 5.2 kg/ha, from the highest amount of straw to the lowest. We conclude that overall, the fertilizer EF is not as relevant as the total emissions, based on this and other studies. Consequently, management practices might be more effective in improving the GHG balance than changing inorganic fertilizer use. We conclude that keeping up to 11 Mg/ha of straw with a large C:N ratio (>100:1) on site might increase sugarcane production sustainability by reducing the greenhouse gas emissions from the field.