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 N(2)O emissions and N(2)O/(N(2)O+N(2)) 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-KNO(3), five split applications of 16 kg ha(-1) N-KNO(3). Cumulative N(2)O emissions for 22 days were unaffected by fertilization treatments at 32% water-filled pore space (WFPS). At 100% and 120% WFPS, cumulative N(2)O emissions were highest from soil fertilized with KNO(3). The split application of N fertilizers decreased N(2)O emissions compared to a single initial application only when KNO(3) was applied to a saturated soil, at 100% WFPS. Emissions of N(2)O were very low after the application of urea, similar to those found at unfertilized soil. Average N(2)O/(N(2)O+N(2)) ratio values were significantly affected by moisture levels (p=0.015), being the lowest at 120% WFPS. The N(2)O/(N(2)O+N(2)) ratio averaged 0.2 in unfertilized soil and 0.5 in fertilized soil, although these differences were not statistically significant.