Objective To improve the container seedlings cultivation level of Cyclobalanopsis gilva with mycorrhiza.

Method Based on the interaction experiments of different slow-release fertilizer addition levels and inoculation of mycorrhizal fungi, the effects of slow-release fertilizer × mycorrhizal fungi on the growth traits and nutrient status of 1-year-old container seedlings of Cyclobalanopsis gilva were analyzed. A split-plot experimental design was used with inoculation of mycorrhizal fungi in the main plot and different slow-release fertilizer addition levels in the sub-plot. The main plot was mycorrhizal treatment, which was divided into two treatments: inoculation (10 mL of Pisolithus tinctorius with a concentration of 36.28 mg·mL⁻¹ was injected into the middle part of the seedling container) and non inoculation. The area was treated with matrix slow-release fertilizer addition, and five slow-release fertilizer addition gradients (1.50, 2.25, 3.00, 3.75, and 4.50 kg·m⁻³) were set.

ResultsInoculation of mycorrhizal fungi promoted the growth of 1-year-old C. gilva container seedlings under different slow-release fertilizer addition levels. There was significant interaction between slow-release fertilizer addition and inoculation of mycorrhizal fungi on total biomass and P utilization index of container seedlings. After inoculation with mycorrhizal fungi, growth traits such as seedling height, caliper, sturdiness quotient, total biomass, total root length and root diameter increased by 18.70%, 7.16%, 10.75%, 24.55%, 1.02% and 18.47% compared with that no inoculation, respectively. N content, N uptake and utilization index, P uptake and utilization index increased by 2.04%, 27.10%, 27.67%, 19.72% and 30.52%, respectively, while P content decreased by 2.94%. There were extremely significant differences in growth traits and nutrient status between inoculated and non-inoculated except total root length and N and P contents. Regardless of whether mycorrhizal fungi were inoculated or not, with the increase of slow-release fertilizer addition level, all growth traits increased first and then decreased except root diameter, P content and uptake showed an overall increasing trend. The growth was the best when the slow-release fertilizer addition level was 3 kg·cm⁻³. The N content and absorption of the container seedlings without mycorrhizal inoculation showed a trend of increasing first and then decreasing, while the N and P utilization indexes decreased first and then increased. There was no obvious change in N content and N absorption.

Conclusion Inoculation of ectomycorrhizal fungus with P. tinctorius can promote the growth of C. gilva container seedlings and improve the nutrient utilization efficiency of N and P, and the effect of promoting mycorrhizal growth is more significant under low slow-release fertilizer addition.. In production, inoculation of mycorrhizal fungi can improve the quality of container seedlings and reduce the use of slow-release fertilizer, which is helpful to the cultivation of high quality seedlings of C. gilva and save seedling cost.