Can alternative N-fertilization methods influence GHG emissions and biomass production in sugarcane fields?
This study evaluated the effect of different N fertilizer application methods on N2O and CH4 emissions and on sugarcane biomass yields over two successive growing seasons. Treatments included three methods of N fertilizer (120 kg ha−1 N) application: 1) above the straw layer; 2) below the straw layer; 3) incorporated into the soil (at 0.1-m soil depth) below the straw layer; and 4) no N application (control). Sugarcane yield for the above straw treatment was, on average, 12% and 15% lower than below the straw and incorporated into the soil, respectively. Emissions of CH4 were very low and unaffected by N fertilizer placement. The method and timing of N application influenced N2O emissions. For both years, higher N2O emissions were observed from the above straw, followed by below straw and incorporated treatments. Except for the above straw treatment during the wet season, the N2O emission factors ranged from 0.08 to 0.62 and were lower than the IPCC default value (1%). The intensity of N2O emissions was, on average, 7.45, 3.97 and 3.3 kg CO2eq Mg stalk−1 for N applied above straw, below straw and incorporated into the soil, respectively. Changes in the N fertilizer placement method and on the timing of application can significantly reduce GHG emissions during sugarcane production, making a significant contribution toward a cleaner production of sugarcane ethanol.