Estimate of bacterial and fungal N2O production processes after crop residue input and fertilizer application to an agricultural field by 15N isotopomer analysis

Abstract Nitrogen fertilizer and crop residue are important sources of N 2 O emission in agricultural ecosystems. This study aims to investigate N 2 O emission and microbial N 2 O production process after potato crop residue input and fertilizer application to an Andosol field. The experiment comprised crop residue treatments as follows: with residue (WR) and without residue (NR). We measured N 2 O emission, N 2 O isotopomer ratios (bulk N isotope ratios and intramolecular 15 N site preference), and environmental parameters to estimate microbial N 2 O production processes. Comparative analysis of N 2 O isotopomer ratios and environmental parameters suggested that nitrification and bacterial denitrification were main N 2 O production processes after N application. Nitrifier denitrification would also contribute to N 2 O production after N application. In contrast, bacterial denitrification and fungal denitrification were important N 2 O production processes in the WR treatment after crop residue input, while nitrification also contributed to N 2 O production. Fungal denitrification was possibly important process during N 2 O peak after crop residue input. These findings reveal that real-time measurements of N 2 O isotopomers performed using a quantum cascade laser spectrometry system are useful for estimating microbial N 2 O production on a field scale.