Effects of N and P fertilization on growth and leaf N and P contents of Betula alnoides clone seedlings

Objective  To reveal the effects of nitrogen and phosphorus additions on growth and leaf nutrient content of Betula alnoides clone seedlings, and select the optimal fertilization formula.

Method  Four B. alnoides clones (A5, FB4, FB4⁺, BY-1) were chosen as the materials and a completely randomized experimental design with nine treatments including three N levels (0, 200 and 400 mg per seedling) and three P levels (0, 70 and 140 mg per seedling) was conducted to compare the differences in seedling height, root collar diameter, biomass, ratio of root to shoot, branch number, leaf area and leaf nutrient content of B. alnoides clones in different fertilization treatments.

Result  Seedling height, root collar diameter, biomass, branch number, ratio of root to shoot and leaf area were significantly affected by fertilization treatment, and the effects of clone-fertilization treatment interaction were significantly different in seedling height, root collar diameter, ratio of root to shoot and branch number. Regardless of the clone, the treatment five had superior seedling height, root collar diameter, biomass, branch number and leaf area, being 2.10%−74.13%, 6.67%−91.45%, 12.24%−358.33%, 2.76%−712.64%, 2.46%−456.31% higher than those of other fertilization treatments, respectively. Leaf N and P contents of different fertilization treatments were significantly different, however there was no significant difference in clones and the interaction between clone and fertilization treatments. The contents of N and P in leaves increased with the additions of nitrogen and phosphorus fertilizers, and additions of nitrogen and phosphorus fertilizers could significantly increase the accumulation of these nutrients in leaves. Seedling biomass, leaf N content, leaf P content and N/P mass ratio were in a parabolic relationship, and they showed a significant positive correlation (P<0.000 1). N/P mass ratio of 15 might be the limiting ratio affecting the growth ofB. alnoides.

Conclusion  Fertilization significantly promotes the growth and improves leaf nutrient contents of B. alnoides seedlings, but there is no significant difference among clones. Based on the seedling growth and leaf nutrient content indexes, treatment five (200 mg N and 70 mg P per seedling) exhibits the optimal growth performance for B. alnoides clones.