Effects of substrate ratio, container size and slow-release fertilizer dosage on the growth of container seedlings of Quercus fabri at different seedling ages

Effects of substrate ratio, container size and slow-release fertilizer dosage on the growth of 1-year-old and 2-year-old container seedlings of Q. fabri were explored, and the optimal seedling cultivation technical scheme was screened out. Using Q. fabri seedlings as materials, an L₉(3⁴) orthogonal design was employed to evaluate three key factors: (1) substrate ratio (Factor A: coir:peat:soil volume ratios of 2:1:1, 1:2:1, and 1:1:2), (2) container size (Factor B: non-woven fabric bags of 8×12 cm, 10×15 cm, and 12×16 cm), and (3) slow-release fertilizer dosage (Factor C: 0, 2, and 4 kg·m⁻³). The growth and biomass index were measured and analyzed. For 1-year-old seedlings, growth was significantly influenced by fertilizer dosage, but not by substrate ratio or container size. All three factors exhibited significant effects on 2-year-old seedlings. The biomass of different treatments was significantly different, and the correlation between biomass and seedling height was greater than other parameters. Considering the growth of seedlings and the cost of raising seedlings, the best combination was A2B2C3, and its mean membership function value was 0.95. Under this treatment, the height and ground diameter of 2-year-old Q. fabri seedlings were 129.01 cm and 1.06 cm respectively. The recommended protocol for cultivating premium 2-year-old Q. fabri container seedlings (height >1.2 m, diameter >1.0 cm) was: 1) 1:2:1 coir:peat:soil substrate, 2) 4 kg·m⁻³ slow-release fertilizer, and 3) 10×15 cm non-woven containers, which could cultivate high-quality 2-year-old container seedlings of Q. fabri with height greater than 1.2 m and ground diameter greater than 1.0 cm.