To select high yield and high nitrogen(N) efficiency of Catalpa bungei clones, a pot experiment with the 10 clones were conducted to observe the economic efficiency of nitrogen utilization, the coefficient of low nitrogen tolerance and stem biomass in response to nitrogen levels, i. e. , high ( + N) and low( - N) nitrogen. The results showed that there existed a significant difference in stem biomass among clones, and the stem biomass was significantly increased by high nitrogen. A significant difference was found in economic efficiency of nitrogen utilization among clones under high nitrogen, in a range from 19. 274 g·g-1 to 28. 055 g"g , whereas there was no significant difference under low nitrogen (26. 403 — 37. 637 g·g-1 ) . The repeatability of economic efficiency of nitrogen utilization was 0. 54 and 0. 78 under low and high nitrogen, respectively. With combination of stem biomass, economic efficiency of nitrogen utilization, low nitrogen tolerance and stem biomass response to nitrogen, appropriate clones were selected for different nitrogen conditions. In consequence, clone 2-7 was suitable for low and high nitrogen conditions, clone 2-8 suitable for low nitrogen, and clone 2-6, 9-1 and 015-1 suitable for high nitrogen conditions.
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