Sugarcane Crop Residue Increases N2O and CO2 Emissions Under High Soil Moisture Conditions

Sugarcane crop residues from green cane harvests may affect the greenhouse gas fluxes from the soils. Therefore, it is important to understand how changes in soil moisture covered with cane trash alter the N2O and CO2 emission. The aim of this study was to evaluate N2O and CO2 emission from repacked soil columns incubated with (16 Mg ha(-1)) or without crop residues and N fertilizer (0 or 2.1 g N m(-2)), and as a function of four soil moisture levels (25, 50, 75 and 100 % of water holding capacity). For gas samplings, the columns were closed with a lid and four gas samples were taken in 20 min. The N2O fluxes increased linearly (p < 0.01) with increasing soil moisture regardless of the residue application on soil. However in the columns with trash the moisture effect, on N2O emission rates, was two-fold greater. Every 10 % increase in moisture in relation to the holding capacity resulted in losses equivalent to 790 and 1,640 mu g N m(-2) for the 0 and 16 Mg ha(-1) crop residue rates, respectively. In conditions of low moisture (25 and 50 %), the crop residue did not increase emissions compared to the bare soil. The CO2 emission also was linearly stimulated with increasing soil moisture, regardless of crop residue application. However, the CO2 emission rate was higher with the residue. Our study indicates that the effects of crop residue on greenhouse gas emissions are exacerbated in periods with high soil moisture.