The Effect Of Long-term Fertilization On GHG Emission From Rice Field And Its Simulation Study

In order to find out the seasonal variation of GHG emission and its driving forces, also further validate DNDC model in double rice field, a manual sampling system was established to monitoring CH₄ and N₂O emission from double rice field in Wangcheng Hunan province. The seasonal variation and daily fluxes of CH₄ and N₂O was also simulated in DNDC model. The reason such as fertilization, soil temperature, soil pH, water management and content of SOC, which affect CH₄ and N₂O flux from rice field was analyzed detailedly in this paper. The fllowing items are the main conclusion of this paper:1. Paddy rice field is the important source of CH₄ and N₂O. Their form of emission are different in seasonal variation. During rice growth period, CH₄ flux is fastened on the period of before drainage, but N₂O flux is fastened on the period during or after drainage. Most of the flux of both CH₄ and N₂O appears in 10 days to 40 days after plant.2 The rank of CH4 average emission in different fertilization treatments is: NPK+straw> NK + manure>CK>NPK. The rank of N2O average emission in different fertilization from early rice field is: NPK>NK+manure>NPK+straw>CK, but from late rice field is: NPK+straw> NPK>NK+manure>CK. Synthetical analyse the greenhouse effect of different fertilization, the treat in NPK is more scientific choice.3. In the range of 15³0℃, CH4 flux from rice field increasing with the soil temperature in 10cm. in the same temperature range, N₂O flux from late rice field after drainage in creasing with the soil temperature in 10cm.4. In the range of pH5-5.8 and pH6.2-6.8, CH4 flux from rice field increasing with the soil pH,there is a linear relationship between CH4 flux and soil pH. In the range of pH6.2-6.8, N2O flux from late rice field before drainage is increasing with the soil pH.5 The CH4 flux from rice field don't correlation with the SOC. Under the effect of the fertilization, CH4 emission from different content of SOC. But CH4 emission is more controlled of management in current year.6. The CH4 and N2O flux from rice field is crossed under water management.During the flooding CH₄ flux is in peak, but N₂O flux is very small. When the rice field is in drainage N₂O flux is in peak, but at the same time CH₄ flux is very small.7 DNDC model can well simulate the N2O flux, SOC, rice yield of long-term variation, air and soil shallow layer temperature. But in modeling in CH4 flux, the effect in late rice is better than early rice Except the simulation on CH4, the DNDC model can apply to the dubble rice field.