NO and NO₂ emissions from intensive vegetable field of Dianchi watershed

Enclosure growth chamber method, which removes the air inlet NO/NO2 first and then monitors NO/NO2 flux of enclosed growth chamber, was used to collect and determine in situ NO/NO2 emission from intensive vegetable field in Dianchi watershed in both dry and rainy seasons. The following results were obtained: 1) The NO/NO2 flux varied diurnally along with the soil temperature, its maximum appeared at noon, and its minimum appeared before dawn; 2) In the celery growth stage, the NO/NO2 flux of CK treatment(bare land) maintained at a certain level; the NO/NO2 flux of NF treatment (N 0 kg/ha) was higher than CK treatment in the mid and late period of celery growth; the NO/NO2 fluxes of LF (N 450 kg/ha) and HF (N 1200 kg/ha) treatments increased gradually because of the celery's growth and frequent N fertilizer application; 3) In dry and rainy seasons, the NO/NO2 emission of CK treatment in the growth stage was NOx-N 1.30 and 1.51kg/ha, respectively, and the NO/NO2 emission of NF treatment in the growth stage was NOx-N 1.07 and 1.44 kg/ha higher than that of CK, respectively; 4) In dry and rainy seasons, the NO/NO2 emission of LF treatment in the growth stage were NOx-N 4.88 and 5.67 kg/ha, which accounted for about 0.79% and 0.92% of applied fertilizer N, respectively; the NO/NO2 emission of HF treatment in the growth stage was NOx-N 7.58 and 10.19 kg/ha, which accounted for about 0.63% and 0.85% of applied fertilizer N, respectively. The NO/NO2-N emission in the growth stage increased with nitrogen fertilizer application rate, but its loss rate does not increase accordingly.