To study the effects of container size, matrix ratio, slow-release fertilizer dosage and placement density on the growth quality of container seedlings of T. sinensis, with the aim of optimizing seedling raising technology, improving seedling quality, and fulfiling the requirements for large-scale planting and industrialization.

In this study, a factorial experimental design was established to include six matrix ratios, three slow-release fertilizer dosages, and three container sizes, resulting in 27 treatment combinations. A comprehensive analysis and evaluation of the growth effects of T. sinensis container seedlings was conducted under different treatments. The effect of different seedling cultivation combinations were comprehensively evaluated using the membership function method. Three kinds of placement densities were set up to analyze the growth difference of container seedlings with different densities.

The impact of container specifications on the base diameter and height-to-diameter ratio of T. sinensis container seedlings was significant (P<0.05) and highly significant (P<0.01), respectively. The matrix ratio and controlled-release fertilizer dosage had a highly significant effect (P<0.01) on both seedling height and base diameter of T. sinensis. Among the interaction of two factors, the combination of matrix ratio × container size, matrix ratio × slow-release fertilizer dosage, and container size × slow-release fertilizer dosage all had highly significant effects on the height of T. sinensis container seedlings (P<0.01). The three-factor interaction of container size × matrix ratio × slow-release fertilizer also significantly affected the height, ground diameter and height-to-diameter ratio of T. sinensis container seedlings (P<0.01). The influence of the three factors on the growth of T. sinensis seedlings was ranked as follows: slow-release fertilizer dosage > container size > matrix ratio. Comprehensive evaluation using the membership function method revealed that the combination of matrix ratio matrix ratio, matrix ratio A6 [V(coconut bran): V(peat): V(soil) = 1: 1: 0] with slow release fertilizer B3 (3 kg/m³) and container size C3 (12.5 cm × 16.0 cm) was better. The A6B3C3 combination resulted in a seedling height, ground diameter and height-to-diameter ratio of 115.73 cm, 12.82 mm and 93.52, respectively, while the A5B3C3 combination resulted in the values of 126.17 cm, 12.20 mm and 107.57, respectively. The planting density of T. sinensis container seedlings is 100/m², and the growth rate is the best.

The matrix ratio, slow-release fertilizer dosage and container size interact on the growth of T. sinensis container seedlings. The A6B3C3 and A5B3C3 combinations with a seedling density of 100/m² can use in container seedling production of T. sinensis, providing a scientific basis for improving the quality of T. sinensis seedlings and optimizing seedling technology.