Phosphorus accumulation and distribution law in continuously-cropped flue-cured tobacco under chernozem natural fertility condition.

The phosphorus accumulation and distribution law in the continuously-cropped flue-cured tobacco under the condition of chernozem natural fertility were studied.The phosphorus accumulation in root system,lower leaves,middle leaves and upper leaves all showed a decreasing trend in harvest time when the continuous cropping years increased.The 3-year continuous cropping was beneficial to the phosphorus accumulation in stem,but the 5-year continuous cropping was not beneficial to it.The continuous cropping for 5 years increased the distribution proportion of phosphorous in root system and middle leaves,while decreased that in stem,lower leaves and upper leaves.Comprehensive analysis indicated that the continuous cropping of flue-cured tobacco should not exceed 5 years.