Nitrous oxide emissions from green tea fields in Japan: contribution of emissions from soil between rows and soil under the canopy of tea plants

This study was conducted to assess the contributions of nitrous oxide (N2O) emissions from soil between rows and soil under the canopy of tea plants (Camellia sinensis (L.) Kuntze) to the entire N2O emissions from tea fields and to determine the factors responsible for changes in N2O emissions. The study was performed in an experimental tea field in which fertilizer application rate was 510 kg nitrogen (N) ha−1 yr−1. N2O flux and soil properties including temperature, water filled pore space (WFPS), ammonium-nitrogen (-N) and nitrate-nitrogen (-N) concentrations, and soil pH were measured over a period of two years. Total N2O emissions from the entire tea field were 10.6 and 14.8 kg ha−1 yr−1 in 2008 and 2009, respectively. Total N2O emissions from soil under the canopy of tea plants were approximately 35% of the total N2O emissions from the entire tea field, suggesting that the contribution of N2O emission from soil under the canopy of tea plants to overall N2O emission was not negligible. A high N2O flux from soil under the canopy was observed when there was heavy rainfall. The key factors for high N2O fluxes observed in soil under the canopy were considered to be increases in soil temperature and WFPS. On the other hand, high N2O fluxes from the soil between rows was observed after fertilizer application in spring and autumn, and there was a significant positive correlation between N2O flux and -N concentration in the soil between rows.