Selection of the optimum fertilizer formula and the effects of nutrient elements on growth and flowering performance of Betula platyphylla.

Three fertilizer formulae (T1, T2 and T3) of various nitrogen, phosphorus and potassium levels were applied to 1, 2 and 3yearold Betula platyphylla seedlings of a halfsib family, respectively, with the objectives of comparing their effects on seedling flowering and fruiting and selecting the optimum one. Then, we investigated the effects of each element (N, P and K) of the optimum formula on growth and development of B. platyphylla seedlings. Results showed that: 1) all formulae significantly increased flowering, compared with no fertilizer (control), with the great response occurring at T3 2) In T3, nitrogen was most effective in improving vegetative growth, making the 3yearold trees reach 3.08 m in height and 25.76 mm in ground diameter, increased by 19.38% and 39.17% respectively than control. 3) Nitrogen fertilizer promoted flowering more effectively than phosphorus or potassium fertilizer. Applying nitrogen improved the flowering rate of 3yearold trees to 49%, compared with only 4%, 1%, and 0 by applying only phosphorus, potassium or without fertilizer. However, applying T3 produced significantly more flowers than applying nitrogen alone, increasing the flowering rate to 90%; 4) During the development from vegetative growth to reproductive growth, some nutrition was allocated for reproductive growth, which reduced the height growth but not diameter growth of the current year.