Nitrogen oxide emissions and soil microbial activities in a Japanese andisol as affected by N-fertilizer management

This experiment was conducted in maize field plots to study the effects of N-fertilizer management on nitrogen oxide emissions, soil microbial activities and crop yield, and the relationships among them in a Japanese Andisol. N fertilization increased both nitrification and dehydrogenase activities in soil and the emissions of NO and NO. Nitrification and dehydrogenase activities showed a close relationship with the NO emission, while the relationship with the N2O emission was not significant. Deep application (8 cm) of N fertilizer generally decreased both nitrification activity and NO emission. Controlled release of N fertilizer decreased the dehydrogenase activity and up to 86% of the NO emission. Our findings indicate the possibility that the low biological NO production in soil by deep application and controlled release of N fertilizer contributed to the low NO emission. Application of controlled release N fertilizer significantly increased the grain yield and N uptake by grain. NO emission showed a negative relationship with maize yield as affected by N-fertilizer management, suggesting the possibility of mitigating NO emission from Andisols without reducing crop production.