Effects of Nitrogen and Phosphorus Foliar Spraying on Nitrogen, Phosphorus and Potassium Reserves of Pinus yunnanensis Seedlings

Purpose To explore the effects of nitrogen and phosphorus foliar spraying on the nutrient element reserves of Pinus yunnanensis seedlings, providing theoretical basis for promoting the cultivation of P. yunnanensis seedlings.

Methods A total of nine treatments with three levels of nitrogen (N) and phosphorus (P) were designed, and two-year old P. yunnanensis was used as the test material for foliar spraying of N and P. N, P and potassium (K) of P. yunnanensis seedlings were determined every two months, and the effects of different fertilization levels on the accumulation, distribution and structural characteristics of the nutrient elements were analyzed.

Results Foliar spraying of N and P could promote the accumulation of N, P and K reserves of P. yunnanensis seedlings. In August, the effect of T₈ treatment (N 0.50%, P 0.40%) was the best on the accumulation of N, P and K reserves in per plants; in October, the effect of T₄ treatment (N 0.25%, P 0.20%) was the best on the accumulation of N, P and K reserves in per plants; in December, the effect of T₇ treatment (N 0.50%, P 0.20%) was the best on the accumulation of P and K reserves in per plants. In different organs, the allocation of N, P and K reserves in leaves accounted for a higher proportion. From the perspective of the allocation of nutrient elements reserves, the T₄ treatment had a better effect on the improvement of N and P reserves allocation in the aboveground part, and the T₅ treatment (N 0.25%, P 0.40%) had a better effect on the improvement of K reserve allocation in the aboveground part. In the structural characteristics of nutrient element reserves, the application of N and P could reduce the root-crown ratio of N, P and K reserves, reduce the stem-leaf ratio of K reserves, and increase the ratio of photosynthetic organs to non-photosynthetic organs of N, P and K reserves.

Conclusion N and P foliar spraying can promote the accumulation of nutrient element reserves in P. yunnanensis seedlings, increase the allocation of nutrient element reserves in stems and leaves, decrease the root-crown ratio. By analyzing the changes of nutrient elements, the suitable nitrogen and phosphorus application amount is screened, providing guidance for promoting the cultivation of P. yunnanensis seedlings.