Mechanistic approach to understand increased N2O emission followed by biochar application to the organic poor field soil

Abstract:

Biochar, which is a by-product of pyrolysis, is widely accepted as a climate change mitigation strategy if it is applied to soils. A lot of researches have reported that application of biochar reduced the emission of N₂O due to better aeration and increased pH. However, in the dry, organic poor, and heavily fertilized Korean field soil, we observed rather an increase in N₂O emission in our previous researches. To explain this inconsistent trend, we conducted a research investigating the mechanisms of N₂O emission. The main mechanisms of N₂O emission from soils are nitrification and denitrification, among which we exclude the possibility of denitrification process because the soil water condition at our sampling dates was dry. To confirm our assumption that the increased N₂O emission from the soil is mainly from the enhanced nitrification due to biochar addition, we used the nitrification inhibitor (DCD: Dicyandiamide). The experiment was performed in the pepper field located in Gyeonggi-do, Korea where we already observed an increase in N₂O emission followed by biochar amendment in the previous year. Treatments include the control, biochar treatment (BC, 2 ton ha^-1), DCD treatment (DCD, 10% of N fertilizer w/w), and biochar and DCD co-treatment (BC+DCD). All the treatments were received with N:P₂O₅:K₂O (225 : 112 : 149 kg ha^-1). Daily average of N₂O emission rate was increased in the BC treatment by 154% and the emission was reduced to the control level in the BC+DCD treatment. From this result, we could confirm that the increased N₂O emission from the biochar application is from the nitrification process. The field experiment will be prolonged to Aug 2015 and for the further analysis, the basic soil physicochemical parameters (TC, TN, pH, hot water extractable C, available N) and microbial parameters (fluorescein diacetate hydrolysis assay, microbial biomass C, and assay of nitrifiers) will be measured.