Potassium fertilization modulates potato (Solanum tuberosum L. V7) yield and rhizosphere microbiome dynamics

Introduction Potassium (K) is a critical macronutrient essential for enzymatic activation, photosynthesis, metabolite transport, and stress resistance in plants. While K is known to influence soil microbial communities, the mechanistic relationships between K fertilization regimes, rhizosphere microbiome assembly, and crop productivity remain to be elucidated. This study investigated the effects of varying K fertilization rates on potato yield and associated rhizosphere microbial community dynamics throughout the key developmental stages. Methods A field experiment using potato ( Solanum tuberosum L. V7) was conducted in Inner Mongolia, China, during the 2024 growing season. Five K fertilization treatments (0, 120, 180, 240, and 300 kg/ha K 2 O) were implemented using a randomized complete block design with three replicates. Rhizosphere soil samples were collected at seedling, tuber initiation, and tuber bulking stages. High-throughput sequencing of bacterial 16S rRNA and fungal ITS1 regions was performed to characterize microbial communities. Taxonomic composition, α-diversity, β-diversity, and linear discriminant analysis effect size was conducted to assess the correlation of potato yield and microbial diversity. Results Potato yield exhibited a quadratic relationship with K application rate, reaching maximum productivity (66,786 kg/ha) at 240 kg/ha K 2 O. Bacterial communities, dominated by Proteobacteria, Acidobacteriota, Actinobacteria , and Gemmatimonadota , demonstrated notable resilience across treatments. Conversely, fungal communities displayed heightened sensitivity to K fertilization, with Shannon diversity indices negatively correlated with yield (r=-0.82, p<0.05). Moderate K application (180-240 kg/ha) significantly enhanced beneficial bacterial populations, particularly Pseudomonas species, while simultaneously suppressing pathogenic Fusarium and maintaining beneficial Mortierellomycota . Both bacterial and fungal communities exhibited distinct successional trajectories, with tuber expansion stage emerging as a critical transition point in community assembly. Discussion This investigation establishes 180-240 kg/ha K 2 O as the optimal application rate for maximizing potato yield while maintaining balanced rhizosphere microbial communities. K influences microbial community structure through multiple mechanisms, including ion-hormone interactions, nutrient activation processes, and pathogen regulation. These findings provide a theoretical framework for developing precision K fertilization strategies that enhance agricultural productivity while promoting the stability of the rhizosphere microbiome in potato cultivation systems.