Regulation of nitrogen, phosphorus, and potassium ratios on carbon and nitrogen metabolism, as well as growth and allocation in Taiwania cryptomerioides

To investigate the effects of different nitrogen (N), phosphorus (P), and potassium (K) fertilization ratios on the accumulation of nitrogen metabolites, soluble sugar content, vegetative growth, and reproductive organ development in 19-year-old Taiwania cryptomerioides. The goal was to identify an optimal N-P-K fertilization scheme to promote its growth and development.

An L₁₆(4³) orthogonal experimental design with three factors (N, P, K) and four levels was employed. The contents of soluble sugar, soluble protein, and total nitrogen were determined in the buds, flowers, and fruits. Additionally, growth parameters of vegetative and reproductive shoots were measured.

1) A comprehensive evaluation indicates that the N3P4K2 treatment has the most significant overall promotional effect on the main agronomic traits. Under this treatment, bud soluble protein content reaches 9.84 mg/g and total nitrogen content is 1.97%, representing increases of 116.26% and 28.76% over the control, respectively. The dry weights of vegetative and reproductive shoots reach 1.21 g and 1.38 g, which are 55.13% and 2.22% higher than the control. Bud soluble sugar content under this treatment is 49.05 mg/g, a 54.68% increase. The N3P2K4 treatment also shows excellent performance, ranking second overall, with increases of 114.95% in bud soluble protein, 26.14% in bud total nitrogen, 47.68% in vegetative shoot dry weight, 1.48% in reproductive shoot dry weight, and 48.50% in bud soluble sugar compared to the control; 2) Nitrogen exerts an extremely significant promotional effect (P<0.01) on soluble protein content and vegetative growth indicators, with effects typically peaking at the N3 level and showing a downward trend at the N4 level. In contrast, total nitrogen content is generally highest at the N4 level; 3) Phosphorus also shows an extremely significant promotional effect (P<0.01) on most measured indicators, with the P3 level performing best for protein and total nitrogen accumulation; 4) The main effect of potassium is not significant (P>0.05) for most metabolic and growth indicators; however, its presence at specific levels is an essential component of the optimal treatments, suggesting a crucial role in nutrient balance and interaction.

A balanced N-P-K application, particularly N3P4K2 and N3P2K4 can significantly optimize nitrogen metabolism and soluble sugar accumulation in Taiwania cryptomerioides.