Effect of long continuous cropping on the yields of flue-cured tobacco and nutrients in soils

A pot experiment with 6 years' continuous tobacco cropping was carried out to investigate the effect of continuous cropping on tobacco yields and soil nutrients. The tested soils are calcareous yellow soil originated from lime stone of Triassic(SL)and clay yellow soil originated from clay of Quaternary(SC). The results show continuous cropping decreased the yields of tobacco leaves in general and varied with soils. Tobacco yields did not show difference in the first three years and decreased afterward on SL, but yields constantly reduced on SC. The concentrations of nutrients in the tobacco leaves, such as nitrogen, phosphorus and potassium, varied with the continuous cropping years. The nutrient absorption was decreased with the prolongation of continuous cropping, but available nutrients were increased with the order: phosphorus＞potassium＞nitrogen. Continuous cropping did not affect the content organic matter，but decreased pH slowly, It might be resulted from the solo application of physiological acidic complex fertilizers. To this effect, applying organic fertilizer was recommended to avoid the soil acidification.