N2O emissions from sugarcane fields under contrasting watering regimes in the Brazilian savannah

Abstract

Bioethanol and other sugarcane by-products, such as the bagasse, are responsible for approximately 12% of Brazil’s total energy generation. This crop is expanding in the Central-Western Region of Brazil, within the Brazilian savannah biome (Cerrado). It is strongly associated with the use of mineral and/or organic fertilizers and irrigation practices due to drought period during winter. However, higher soil moisture content (due to rain or irrigation) and nitrogen (N) application increase nitrous oxide (N 2 O) emission, which is one of the main greenhouse gases from the agricultural sector. This study aimed to evaluate soil N 2 O fluxes in sugarcane under field conditions with contrasting water regimes in the Cerrado region of Brazil. Due to watering regimes, based on different crop evapotranspiration demand, it was possible to establish adequate water-use efficiency technologies. Increases in watering regimes did not increase N 2 O emissions compared to “rescue irrigation”, commonly used by farmers in the region. However, higher yields were obtained from the higher watering regime (T75%) compared to the farmers’ common practice. • The highest N 2 O redfluxes occur between 50 and 60% WFPS. • Ammonium sulfate fertilizer increases NH 4 + in soil and promotes lower N 2 O emissions. • Water regime that attends 75% of plant demand mitigates N 2 O emissions and increases. sugarcane yield.