Effects of different fertilizer levels on N2O flux from protected vegetable land

To identify the characteristics of N2O emission from protected vegetable land in Beijing, and to seek a way that decreases N2O emission and increase or keep cucumber yield, with the method of static chamber-gas chromatograph technique, N2O emission was monitored in cucumber field from protected vegetable land in Beijing. The effects of different amounts of fertilization on N2O emission, vegetable yields and economic benefit were analyzed. The results showed that significant temporal variability of N2O flux from all treatments was observed in different growing stages of cucumber. Larger emission happened at the initial stage of the experiment. N2O emission decreased and remained stable with time. At the late stage, a peak emission happened and continued for a long time because of larger amount of top dressing. The order of total N2O emission was: T4 (conventional fertilization + chicken dug，in short “CF+CD”) >T3 (3/4CF+CD) > T1 (1/4CF+CD) > T2 (1/2CF+CD) > Tn (CD) > T0 (Control treatment), and there existed significant difference between treatments. By considering fertilizer rates, N2O emission and cucumber yield, it was concluded that the fertilization rate of T3 (3/4CF+CD) was very reasonable, which could provide basis for applying fertilizer rationally, reducing farm production costs, estimating greenhouse gas emissions from cropland and compiling national greenhouse gases emission inventory