Diurnal Variation of CO₂ Emission Fluxes in Flue-cured Tobacco Field at Ceiling Period in Enshi of Hubei Province

Diurnal variation of CO₂ emission fluxes in a flue-cured tobacco field at ceiling period under different organic fertilizer treatments were measured by closed chamber-infrared method. The results showed that the CO₂ emission fluxes from ecosystem of tobacco field had obvious diurnal variation at ceiling period, The maximum emission flux appeared at 17:30-19:30, while the minimum at 11:30-15:30. The variation of CO₂ emission fluxes was negatively correlated with soil moisture content significantly. Organic fertilizer application promoted CO₂ emission fluxes in the tobacco field significantly, and there was no significant difference between the rapeseed cake fertilizer and the bio-organic fertilizer from tobacco stems. The diurnal variation of CO₂ emission fluxes from soils in the tobacco field fluctuated slightly. The maximum emission flux appeared at 9:30, while the minimum at 7:30. The variation of CO₂ emission flux was significantly or highly significantly and positively correlated with air temperature, surface temperature, 5cm, and 10 cm soil temperature. CO₂ emission fluxes of tobacco field ecosystem mainly came from net photosynthesis of tobacco, but not from soil respiration. Furthermore, the degree of diurnal variation of CO₂ emission fluxes in tobacco field ecosystem was higher than that in soils in tobacco fields.