Soil N2O emissions and N2O/(N2O+N2) ratio as affected by different fertilization practices and soil moisture

The objective of this work was to evaluate the effect of the chemical nature and application frequency of N fertilizers at different moisture contents on soil N2O emissions and N2O/(N2O+N2) ratio. The research was based on five fertilization treatments: unfertilized control, a single application of 80 kg ha−1 N-urea, five split applications of 16 kg ha−1 N-urea, a single application of 80 kg ha−1 N–KNO3, five split applications of 16 kg ha−1 N–KNO3. Cumulative N2O emissions for 22 days were unaffected by fertilization treatments at 32% water-filled pore space (WFPS). At 100% and 120% WFPS, cumulative N2O emissions were highest from soil fertilized with KNO3. The split application of N fertilizers decreased N2O emissions compared to a single initial application only when KNO3 was applied to a saturated soil, at 100% WFPS. Emissions of N2O were very low after the application of urea, similar to those found at unfertilized soil. Average N2O/(N2O+N2) ratio values were significantly affected by moisture levels (p = 0.015), being the lowest at 120% WFPS. The N2O/(N2O+N2) ratio averaged 0.2 in unfertilized soil and 0.5 in fertilized soil, although these differences were not statistically significant.