Nitrogen distribution and efficiency difference of Catalpa bungei C.A.Mey. clones at nursery stage

In order to develop the high nitrogen efficiency Catalpa bungei C.A.Mey clones,an experiment was carried out to observe nitrogen distribution characteristics and nitrogen efficiency of ten Catalpa bungei C.A.Mey clones treated with the high(+N) and low(-N) nitrogen.The results showed that more nitrogen distributed to the underground part(rootleafstem) under the low nitrogen treatment,while situations under the high nitrogen treatment was contrary(leafstemroot).There was no significant difference on nitrogen distribution between clones.Nitrogen efficiency of clones significantly higher under high nitrogen than low nitrogen,but variation degree among clones under low nitrogen was higher than that under high nitrogen.Variation degree of both of nitrogen absorption efficiency and nitrogen utilization efficiency was much higher under low nitrogen.Increasing nitrogen application rate could improve nitrogen absorption efficiency significantly,but declined nitrogen utilization efficiency.Based on the results of correlation analysis,nitrogen absorption efficiency contributed more to the nitrogen efficiency than nitrogen utilization efficiency.Nitrogen efficiency of 2-7 and 015-1 clones were higher than others under both high and low nitrogen treatments.