| Farming activities emitted greenhouse gases (GHGs) have becoming one of the most important concerns which result in the global warming. N2O emitted mainly from upland soils and CH4 emitted mostly from paddy soils are two of the important emission contributors of fanning systems to atmospheric greenhouse gases. Based on the background, three aspects constitute the content of this study: i)The greenhouse gas fluxes (CO2 N2O CH4) from the typical upland soils under winter wheat - summer corn, rotation systems in northern China was measured, and. the relationships between GHGs and the relevant factors were analyzed such as the turn-over of soil carbon and nitrogen, soil temperature, fertilization etc. ii) The greenhouse gases emitted from typical double rice fields in Jiangxi province were simulated using the DNDC model, and the emission characteristics in different sub-region was analyzed too. iii) The GHGs emitted from farming soils along the North-South Transect of Eastern China (NSTEC) were also simulated using DNDC model, and some possible suggestions to abate the emission of GHGs were proposed based on analyzing the simulated results.The average emission flux of CO2 under the growing seasons of winter wheat - summer corn rotation systems was: treatment with inorganic-organic fertilizers (110.78 mg CO2/m2/h) > treatment with only inorganic fertilizers (79.58 mg CO2/m2/h)> treatment without nitrogen addressing (74.20 mg CO2/m2/h) > fallow treatment (54.91mg CO2/m2/h). Plant growth status and soil temperature were two main factors which affect the soil respiration intensity, for example, soil CO2 showed higher emission flux at the elongation stage for wheat and through elongation to horn stages for corn. As soil dissolved organic carbon (DOC) is the internal product of decomposition process of complicated plant materials, it did not show directly relationship with soil CO2 flux. The N2O emission flux from the soil was mainly influenced by fertilization and soil inorganic nitrogen, also the temperature. When fertilizers were dressed under relatively higher air temperature, the content of soil inorganic nitrogen increased, and resulted in the higher emission flux of N2O, while the N2O flux peak was lagged than the fertilization time. The average emission flux of N2O during the growing seasons was: treatment with inorganic-organic fertilizers (39.86 ug N2O-N/m2/h ) > treatmentwith only inorganic fertilizers (34.62 ug N2O-N/m2/h) > treatment without nitrogen addressing (21.74 ug N2O-N/m2/h) > fallow treatment (2.48 ug N2O-N/m2/h). Since methane emission flux from the upland soils was affected by many factors (such as temperature, soil moisture, soil oxygen pressure, fertilizer types and rate, tilling etc.No obvious methane emission characteristics was found under this field experiment The measurement results indicated that the upland soil was a weak methane sink. The average emission flux of CH4 during the growing seasons was: treatment with inorganic-organic fertilizers (-9.7 ug CH4m2/h) > treatment with only inorganic fertilizers (-16.0 ug CH4m2/h) > treatment without nitrogen addressing (?6.5 ug CH4m2/h) > fallow treatment (28.8 ug CH4m2/h)The GHGs emission in Jiangxi province simulated using DNDC model had the following characteristics: For the CO2 emission flux from the paddy soils, it increased with the increase of soil fertility, and had little difference among sub-regions. For the CH4 emission flux, it increased with the increase of soil pH at the range of pH 4.5-6; while it decreased with the increase of the content of soil clay under the same pH condition. In the rice field, N2O emission happened mainly at the aeration period, and fertilizer rate and soil pH were the key factors which affect the N2O emission flux-relatively higher N2O flux was found when the fertilizer rate was higher, and the N2O flux was found higher in neutral soils than in acid soils. For the tot...
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