Fertilization regimes regulate root rot resistance in Apocynum venetum under long-term continuous cropping via modulation of the rhizosphere microbial community and soil properties

Apocynum venetum is an important industrial fiber and medicinal crop，which can be severely affected by disease, particularly root rot. To address the risks of vegetation degradation and aggravated root rot associated with long-term monoculture and intensive fertilization, we conducted field experiments to clarify how different fertilization regimes affect the growth, root rot incidence, and rhizosphere microecology. The results showed most fertilizer treatments enhanced soil available nitrogen, phosphorus, and increased vegetative growth, but a double-rate nitrogen–phosphorus treatment decreased plant biomass and significantly increased root rot severity. In contrast, a double-rate organic amendment effectively suppressed root rot disease. Rhizosphere microbial analyses showed that mineral fertilization disrupted the microbial community balance, and increased the proportion of potentially pathogenic fungi, thereby elevating the risk of root rot. Organic fertilization improved the rhizosphere environment, and selectively enriched putatively beneficial taxa such as Candidatus-Entotheonella , contributing to a disease-suppressive community. Furthermore, soil organic matter and available phosphorus interacted to modulate key microbial groups, forming a core regulatory network that links soil fertility with plant health. Overall, our results indicate that imbalanced chemical fertilization destabilizes rhizosphere microecology and promotes disease, whereas organic or integrated organic–inorganic fertilization supports A. venetum growth and enhances resistance to root rot by improving soil properties, optimizing nutrient availability, and restructuring the microbial community. These findings provide important knowledge for designing fertilization strategies to manage root rot in A. venetum production systems. • Excess/imbalanced NP disturbed rhizosphere ecology, increasing A. venetum root rot. • High NP raised soil NO₃⁻-N and available P, linked to higher disease incidence. • Sole organic fertilization reduced root rot by boosting SOM and beneficial microbes.