NOX fluxes from several typical agricultural fields during summer-autumn in the Yangtze Delta, China

NOX fluxes from three kinds of vegetable lands and a rice field were measured during summer–autumn in the Yangtze Delta, China. The average NO fluxes from the rice fields (RF), celery field (CE), maize field (MA) and cowpea field (CP) were 4.1, 30.8, 54 and 32.2 ng N m−2 s−1, respectively; and the average NO2 fluxes were −2.12, 0.68, 1.33 and 0.5 ng N m−2 s−1, respectively. The liquid N fertilizer (the mixture of swine excrement and urine) which is widely applied to vegetable lands by Chinese farmers was found to quickly stimulate NO emission, and have significant contribution to NO emission from the investigated vegetable lands. Apparent linearity correlations were found between NO2 fluxes and the ambient concentrations of the rice fields, with a compensation point of about 2.84 μg m−3. Total emissions of NO during summer–autumn time from this area were roughly estimated to be 4.1 and 8.4 Gg N for rice field and vegetable lands, respectively.