Effects of slow-release fertilizer and microbial agents on the growth of <i>Cymbidium ensifolium</i> 'Dongfang Honghe' cultivated in substrate

<italic>Cymbidium ensifolium</italic> is a representative species of national orchids, which has both ornamental and economic value. Its high-quality hybrid variety 'Dongfang Honghe' is highly favoured for its lotus petal flower type and long flowering period. However, the shortage of substrate resources such as perlite and the low fertilizer utilization rate in traditional cultivation restrict its large-scale production. In this study, a three-factor and five-level quadratic regression universal rotation combination design was employed to investigate the effects of substrate ratio, microbial agents, and slow-release fertilizer on the growth of <italic>Cymbidium ensifolium '</italic>Dongfang Honghe'. Analysis of variance revealed that T15 (Chinese fir block : perlite ratio of 3:4, Effective Microorganisms (EM), and 20 grains of Osmocote No. 601) significantly affected seedling height, leaf number, root parameters, leaf total nitrogen content, and total phosphorus content compared to the other treatments. Furthermore, the leaf count, along with the total nitrogen and total phosphorus content in the leaves was increased with the application of the EM and an appropriate quantity of slow-release fertilizer (20 grains of Osmocote No. 601). The total nitrogen content in the leaves was significantly reduced by the microbial agent Osmocote No. 601, while the interaction of the matrix ratio and Osmocote No. 601 significantly enhanced the total phosphorus content in the leaves. Therefore, T15 was the optimal combination for plant growth and development. This provides a theoretical foundation and efficient reproduction of orchids, as well as technical guidance for the management and cultivation of <italic>C. ensifolium</italic>.