Nitrogen Transformation And N₂O Emmissions From Vegetable Soils Under Different Mode Of Agriculture Production

Vegetable production is the typical representative of agriculture production that highly consumes resources in China. The proportion of vegetable production in planting structure has increased in recent years. Most scholars did research on nitrogen transformation and N2O emissions of rice and wheat field in China. However, the scientific literature regarding nitrogen transformation and N2O emission in vegetable soils is rare, and nobody research on organic vegetable soils under open-air and greenhouse cultivation systems in China. With the field experiments and incubation experiments in laboratory, we studied on nitrogen transformation and N2O emission under different mode of vegetable production, which were open-air conventional vegetable production (OC), open-air organic vegetable production (OO) and greenhouse organic vegetable production (GO) in Nanjing suburbs. It is important in seeking for the suitable agriculture production and reducing greenhouse gases emissions in China. The results of this study are presented as follows:1. The nitrogen mineralization, nitrification and denitrification of open-air conventional vegetable soils were more intensive than that of open-air organic vegetable soils. Higher nitrogen mineralization in open-air conventional soils might be related to organic carbon, total nitrogen, C/N and pH, while increased nitrification might be related to pH.2. Overall, the nitrogen mineralization, nitrification and denitrification of greenhouse cultivated organic soils were stronger than that of open-air organic soils. Greater nitrogen mineralization in greenhouse cultivated organic soils might be related to total nitrogen, C/N and microbial activity, while increased nitrification was probably attributed to microbial activity, and higher denitrification might be related to C/N and microbial activity3.The N2O cumulative emissions from open-air conventional soils were significant higher than those from open-air organic soils in nitrification processe, pH and substrate NH4+-N of the soils were identified key factor in N2O cumulative emissions. The N2O cumulative emissions from open-air organic soils were significant greater than those from open-air conventional soils in denitrification processe, which might be related to pH of the soils4. The N2O cumulative emissions from greenhouse organic soils were significant higher than those from open-air organic soils in nitrification processe, substrate NH4+-N and C/N of the soils were identified key factor in N2O cumulative emissions. The N2O cumulative emissions from greenhouse organic soils were greater than those from open-air organic soils in denitrification processe, but the difference was not significant.5. The fluxes of N2O emissions during vegetable growing period in open-air conventional soils and greenhouse organic soils were no significant correlate with soil moisture. However, the fluxes of N2O emissions during Chrysanthemum leaf growing season in open-air organic soils were positively correlated with soil moisture. The correlativity can be described with index function which was y=13.33e00468x (F represent fluxes of N2O emissions; x represent soil moisture,23%<x<72% WFPS). The fluxes of N2O emissions during vegetable growing period in open-air conventional soils, open-air organic soils and greenhouse organic soils were no significant correlate with soil temperature. Fertilization can obviously promote the fluxes of N2O emissions under different mode of vegetable production, and the sequence of emission factor was EFOC (1.15%)>EFoo (0.34%)>EFGO (0.06%).6. The nitrogen transformation of open-air conventional vegetable soils was more intensive than that of open-air organic vegetable soils. The nitrogen transformation of greenhouse organic vegetable soils was more intensive than that of open-air organic vegetable soils. Compare with conventional vegetable production, organic vegetable production has more potential in reducing N2O emissions in vegetable, and greenhouse organic vegetable production is more capable of reducing N2O emissions.