Dolomite-Loaded Vermicompost Improves Acidic Soil Health and Promotes Panax quinquefolius L. Growth in Pine Agroforestry Systems

Agriforestry systems are essential for improving the quality of medicinal herbs and ensuring the sustainable management of forests. Forest soil acidification inhibits the growth of medicinal plants. The application of novel dolomite-loaded vermicompost (DOVC) is considered a potential method for promoting plants growth. However, the mechanisms by which it promotes the growth of medicinal plants are poorly understood. This study combined observational analysis and field experimentation, to first elucidate the correlation between under-forest soil pH and root dry weight of American ginseng (Panax quinquefolius L.). Subsequently, the mechanisms by which DOVC promotes the growth of P. quinquefolius were analyzed from the perspectives of plant physiology and soil microbiome. The results indicate: (1) Field survey results demonstrated when the pH was between 5.28 and 5.99, the root dry weight of P. quinquefolius gradually increased with increasing soil pH. (2) Compared with Control, DOVC increased the soil pH by 1.48 units and promoted the growth of P. quinquefolius, with a net photosynthetic rate increase of 60.26%, malondialdehyde content decrease of 71.07%, and root dry weight increase of 50.33%. (3) Compared with Control, DOVC enhanced bacterial community diversity, with Ace and Chao 1 indices increasing significantly by 33.88% and 25.18%, respectively; and increased the relative abundance of Chloroflexi and Basidiomycota. (4) Partial Least Squares Path Modeling revealed that DOVC positively influenced P. quinquefolius growth via the improvement of soil health index and microbial community diversity. The development of this novel soil amendment offers a new approach to improving soil health in agroforestry systems.