Nanosilicon-based vermicompost leachate and Trichoderma harzianum promote the growth of Panax quinquefolius L. cultivated under forests by improving soil enzyme activity

Abstract

Planting vegetation under forests in agroforestry systems fosters sustainable agricultural development. However, Limited availability of biostimulants for agroforestry and unclear mechanisms of plant growth promotion. This study synthesized and evaluated a novel biostimulant, nanosilicon-based vermicompost leachate (NSVCL), using Panax quinquefolius L. as the research plant species for forest cultivation. Trichoderma harzianum (TH) was chosen to represent a biostimulant with broad-spectrum properties, and its application effects were compared with NSVCL. The regulatory effects of both on the physiological characteristics and rhizosphere soil microenvironment of P. quinquefolius were investigated, with untreated plants serving as controls. Compared to the control, NSVCL and TH increased the dry weight of P. quinquefolius roots 129.33 % and 23.50 %, respectively. NSVCL was applied more effectively than TH. Additionally, NSVCL markedly improved leaf anatomical traits, including palisade and spongy tissue thickness, overall leaf thickness, chloroplast number, and cuticle thickness. Application of NSVCL and TH significantly elevated the net photosynthetic rate (Pn) by 86.55 % and 60.92 %, respectively, and increased total chlorophyll content (TChl) by 24.91 % and 11.76 %. Biostimulants facilitated nutrient uptake and boosted antioxidant enzyme activity in P. quinquefolius. Partial least squares path modeling (PLS-PM) further demonstrated that both NSVCL and TH promoted plant growth by enhancing soil enzyme activity in forest environments. These findings underscore NSVCL's efficacy in improving P. quinquefolius growth under forest conditions and provide a practical foundation for advancing organic forest cultivation and sustainable forest-medicine integration.