The Nutrients Changes of Paulownia's Leaves in the Growing Season

The Nutrients changes and the nutrient levels in different canopy layers of 2-year-old Paulownia fortunei Yulinensis in a growing season were studied under the natural condition. The results showed that: ①N concentration decreasesd as a saw shapes in the whole growing season. The highest was 42.0 g·kg-1; the lowest was 21.5 g·kg-1. P concentration decreased in the beginning and extended to be steady from June to October, then, kept the descending trend again. The highest was 2.5 g·kg-1; the lowest was 1.2 g·kg-1. K concentration decreased in the beginning and extended to be steady from June to October, then, kept the descending trend till November, and extended to be steady again. The highest was 14 g·kg-1; the lowest was 6.6 g·kg-1. ②The nutrient content of a whole tree showed descending trend in the beginning and turned to increasing trend till July and decreased till September and increased slowly till the end of the growing season. The highest contents of N,P,and K were 7.26 g·tree-1,0.37 g·tree-1,and 2.3 g·tree-1 which appeared in the end of July;and the lowest was 3.2 g·tree-1,0.16 g·tree-1,and 0.96 g·tree-1 which appeared in September. ③The nutrient content(N,P and K) per leaf kept increasing in the whole season. ④ There was no difference for nutrient element content in different canopy layers.