Reasonable fertilization can improve soil fertility, increase trees resistance to pests and diseases, and improve wood yield and quality. To explore the effects of proportionate fertilization on the growth, photosynthesis, leaf nutrient content and leaf anatomical traits of T. amurensis, and provide theoretical reference for the efficient fertilization technology of T. amurensis.

Using 7-year-old Tilia amurensis as experimental materials, used N, P, K 3 factors 3-level orthogonal test L₉(3⁴), set up different fertilization ratios treatments, including T1 (N₁P₁K₁), T2 (N₁P₂K₂), T3 (N₁P₃K₃), T4 (N₂P₁K₂), T5 (N₂P₂K₃), T6 (N₂P₃K₁), T7 (N₃P₁K₃), T8 (N₃P₂K₁), T9 (N₃P₃K₂), a total of nine treatments and the CK, to determine leaf nutrient content, gas exchange parameters, anatomical traits, and tree height and diameter growth.

1) Rational fertilization could significantly (P < 0.05) increase the height and diameter growth of T. amurensis, both of which were highest in the T5 treatment, which increased 155.86% and 115.92%, respectively, compared with CK. 2) there were no significant changes in the total N and total P contents of the leaves of T. amurensis treated with different ratios of fertilization, and the leaf N and P contents were the highest in T1 and T2, respectively, but the leaf N∶K values were significantly elevated (P < 0.05), the leaf total K and K∶P values were significantly reduced, and the K content was the lowest in T9, which was lower than that of the CK by 32.5%. 3) The net photosynthesis rate, transpiration rate, stomatal conductance and inter-cellular CO₂ concentration of leaves of Tilia amurensis treated with different fertilizer ratios were significantly different from those of CK (P < 0.05). Among them, the net photosynthetic rate was greatest at T4, transpiration rate and stomatal conductance reached the maximum at T5, and the inter-cellular CO₂ concentration was the best at T3. 4) proportionate fertilization had a significant effect (P < 0.05) on the structure and tissue thickness of the leaves of T. amurensis, and there was no significant effect on leaf tissue compactness. Among them, the ratio of palisade tissue to spongy tissue was higher than that of CK, and treatment T5 showed the best performance in palisade tissue and spongy tissue ratio, which was 65.96% higher compared with CK. The differences between leaf tissue porosity and control were all non-significant, ranging from 0.29 to 0.42; leaf tissue compactness was significantly higher than that of control in all treatments (P < 0.05), but there was no significant difference between treatments, ranging from 0.31 to 0.49.

Reasonable N, P and K ratio fertilization could improve the photosynthetic capacity and nutrient accumulation capacity of T. amurensis, and promote the growth of T. amurensis. Taken together, the treatment of T4 was the most effective in this experiment, i.e., the fertilization rates of CO(NH₂)₂, Ca(H₂PO₄)₂ and KCl were 28.3, 42.9 and 10.8 g per plant, respectively.