Nitrous Oxide Emissions From Household Vegetable Fields in The Rural Residential Areas of Hilly Subtropical Central China

Abstract

Nitrous oxide (N2O) emissions from a household vegetable field in a rural residential area of hilly subtropical central China were observed using a static chamber-gas chromatographic method from January 2010 to December 2011. The N2O fluxes exhibited seasonal dynamics and the accumulated N2O emissions during the wet seasons accounted for 83.5% of the total N2O emissions. Soil mineral nitrogen (N) contents were found not limiting factors because of the application of large amounts of human excreta. The daily N2O fluxes showed a significant, positive correlation with soil temperature, soil moisture and soil NO3 --N content, and soil denitrification may be the major pathway responsible for N2O emissions. High-frequency, intensive application of liquid excreta stimulated the N2O emission process. The average annual N2O emission rate was 12.1 ± 0.9 kg N ha-1 year-1 in the examined household vegetable field, and the total N2O emissions from household vegetable fields originating from the N source of human excreta in the studied Jinjing catchment (135 km2) were estimated as 1.58 ± 0.16 ton N year-1. Such emissions can be considered as N2O re-emissions of the N input into the ecosystem, and the emission factor of N2O re-emissions was estimated to be 0.57%. The findings indicated that under the present management practices, household vegetable fields in the subtropics of China provide a relevant contribution to greenhouse gas emissions and a responsive mitigation scheme at a household scale is needed to reduce N2O emissions.