Effects of cracks and some key factors on emissions of nitrous oxide in paddy fields

Paddy field is a primary agricultural landscape in the south of China and is often regarded as one of main sources emitting nitrous oxide to atmosphere. The nitrous oxide emissions under a variety of paddy field practices, such as fertilization, flooding/draining management were investigated to study on agricultural activities on paddy field affect the dynamic process of the emission. Under no addition of fertilizers the average emission flux of nitrous oxide was 8.55 microg/(m2 x h) during the rice( Oryza Sativa L. ) growth season. The results indicated that most of nitrous oxide emissions occurred during the crack forming-and-expansion period when paddy field was being drained. The diurnal emissions peak of nitrous oxide appeared at 20:30 at night in cracked rice fields. The statistical analysis suggested that the correlation of nitrous oxide emissions flux ( Y) with soil water content ( X1 ), soil temperature ( X2 ), and Eh ( X3 ), could be described in a regression equation: Y= - 1498.95 + 2895.48X, + 50.63 X2 - 96.99X1 x X2 + 0.006X2 x X3. There were the different power equations to simulate the correlations between the everyday dynamic N2O emissions and the mean surface area of cracks, mean volume and depth of cracks respectively during paddy soil drying by soil columns incubation experiments. Taken all together, the current study presented a dynamic analysis of nitrous oxide emission of paddy field under various conditions, therefore provided a basis for the management to balance between environmental effect and paddy field activities.