Abstract: In order to understand the effects of fertilization, planting and climate on soil N supply, field trials were conducted in Jiaoyuan Town, Xuan’en County with high frequent sampling of the field trial plots. Zero-tobacco planting and zero-fertilization were used as the control (CK) in the experiment. In the trials, rainfall and air temperature came from Enshi Meteorological Agency. Results show that soil alkali-hydrolysis N content increases with increasing air temperature, but decreases with increasing rainfall; generally lagging behind rainfall by 5~10 days. For a period of about 45 days, soil alkali-hydrolysis N content significantly increases under fertilization with no plastic film cover. Under combined organic and chemical fertilization, soil alkali-hydrolysis N supply improves in mid- to late-growth stages of tobacco. This is therefore an effective way of regulating N supply during later growth stage of tobacco. The order of significance of the factors affecting soil alkali-hydrolysis N content is planting > fertilization > climate. Cultivation factors such as crop absorption, film mulching are the main factors affecting soil alkali-hydrolysis N content.