Nitrous oxide emission derived from soil organic matter decomposition from tropical agricultural peat soil in central Kalimantan, Indonesia

• Published in: Soil science and plant nutrition (Tokyo) 2011-06, Vol.57 (3), p.436-451
• Main Authors: Toma, Yo, Takakai, Fumiaki, Darung, Untung, Kuramochi, Kanta, Limin, Suwido H., Dohong, Salampak, Hatano, Ryusuke
• Format: Article
• Language: English
• Subjects: carbon dioxide; Decomposition; denitrification; Nitrogen; nitrous oxide; organic matter decomposition; Soils; tropical peatland
• ISSN: 0038-0768; 1747-0765
• DOI: 10.1080/00380768.2011.587203

Our previous research showed large amounts of nitrous oxide (N 2 O) emission (>200 kg N ha −1  year −1 ) from agricultural peat soil. In this study, we investigated the factors influencing relatively large N 2 O fluxes and the source of nitrogen (N) substrate for N 2 O in a tropical peatland in central Kalimantan, Indonesia. Using a static chamber method, N 2 O and carbon dioxide (CO 2 ) fluxes were measured in three conventionally cultivated croplands (conventional), an unplanted and unfertilized bare treatment (bare) in each cropland, and unfertilized grassland over a three-year period. Based on the difference in N 2 O emission from two treatments, contribution of the N source for N 2 O was calculated. Nitrous oxide concentrations at five depths (5-80 cm) were also measured for calculating net N 2 O production in soil. Annual N fertilizer application rates in the croplands ranged from 472 to 1607 kg N ha −1  year −1 . There were no significant differences in between N 2 O fluxes in the two treatments at each site. Annual N 2 O emission in conventional and bare treatments varied from 10.9 to 698 and 6.55 to 858 kg N ha −1  year −1 , respectively. However, there was also no significant difference between annual N 2 O emissions in the two treatments at each site. This suggests most of the emitted N 2 O was derived from the decomposition of peat. There were significant positive correlations between N 2 O and CO 2 fluxes in bare treatment in two croplands where N 2 O flux was higher than at another cropland. Nitrous oxide concentration distribution in soil measured in the conventional treatment showed that N 2 O was mainly produced in the surface soil down to 15 cm in the soil. The logarithmic value of the ratio of N 2 O flux and nitrate concentration was positively correlated with water filled pore space (WEPS). These results suggest that large N 2 O emission in agricultural tropical peatland was caused by denitrification with high decomposition of peat. In addition, N 2 O was mainly produced by denitrification at high range of WFPS in surface soil.