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

Abstract

Our previous research showed large amounts of nitrous oxide (N 2 O) emission (4200 kg N ha À1 year À1 ) 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 À1 year À1. 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 À1 year À1 , 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.

Efflux of Soil Nitrous Oxide from Applied Fertilizer Containing Organic Materials in Citrus unshiu Field in Southwestern Japan

“…Based on the calculation method provided by Toma et al [13], the emission factor for N 2 O (EF) was calculated using annual N 2 O emission (kg N ha −1 ·year −1 ) and applied N (kg N ha −1 ·year −1 ) as following equation:…”

Land use change affects microbial biomass and fluxes of carbon dioxide and nitrous oxide in tropical peatlands

“…The thickness of the peat was 2.6-2.8 m. The bulk density and porosity of the surface soil (0-10 cm) were approximately 0.4 g cm −3 and 73-88%, respectively. The C and N contents of the surface soil (0-10 cm) ranged from 530 to 632 and 13 to 14.3 g kg , respectively (Toma et al 2011). The vegetation that existed before the forest fire consisted mostly of deciduous trees, such as Tetramerista glabra Miq., Calophyllum sp., Shorea sp., Combretocarpus rotundatus (Miq.)…”

“…In studying the characteristics of peat soils, it was found that some agricultural peat soils emit large amounts of nitrous oxide (N 2 O), which is derived from soil organic nitrogen (N) (Toma et al 2011). Although the N 2 O emissions from tropical peatlands tend to be higher and more varied compared with those of other soils, the impacts of land use management on the conversion rate of soil organic N to N 2 O have yet to be clarified.…”

“…Peat swamp forests as well as other forests on mineral soils have been logged intensively through the official concession system, and the canals that are dug into the surface of the peat soils enhance the drainage to decrease the groundwater level, exposing the peat soils to the risk of fire and microbial decomposition (Wösten et al 2008). In addition, a large portion of the tropical peatlands in Southeast Asia have since the 1970s been drained and converted to agricultural land to accelerate microbial decomposition, which results in significant C outputs to the atmosphere, contributing to climate change processes (Page et al 2002;Takakai et al 2006;Hirano et al 2007;Jauhiainen et al 2008;Toma et al 2011).…”

Protocols for the measurement, monitoring, and reporting of structure, biomass, carbon stocks and greenhouse gas emissions in tropical peat swamp forests

“…The largest greenhouse gas flux to the atmosphere is CO 2 , which is produced during plant respiration (autotrophic respiration), decomposition (heterotrophic respiration) and rapid oxidation during fires (land cover change). The saturated soils and anaerobic nature of undisturbed (Hadi et al 2005;Novita 2016), but upon agricultural conversion and with use of fertilizers, N 2 O emissions significantly increase (Toma et al 2011;Novita 2016).…”