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

Abstract

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 K₂O) 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 K₂O. 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 K₂O 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.

Keywords: microbial diversity; potassium fertilization; potato yield; rhizosphere microbiome; sustainable agriculture.

Figure 1

Principal coordinates analysis (PCoA) of rhizosphere microbial communities. PCoA plots based on Bray-Curtis distances showing (A) bacterial communities and (B) fungal communities at the genus level in potato rhizosphere. Colors represent potassium fertilizer treatments. Symbols indicate growth stages: circles= seedling, triangles= tuberogenesis, squares= tuber expansion.

Figure 2

Rhizosphere microbial community composition of potatoes at different growth stages under varying potassium fertilizer treatments. Relative abundance (%) of bacterial communities at (A) phylum and (B) genus levels, and fungal communities at (C) phylum and (D) genus levels in potato rhizosphere soil. Communities were analyzed across three developmental phases (seedling, tuberogenesis, and tuber expansion stages) and five potassium fertilizer treatments (CK, T120, T180, T260, and T320). Bar charts display the top 20 most abundant taxa. The y-axis shows relative abundance percentages.

Figure 3

Linear discriminant analysis effect size (LEfSe) of microbial communities in potato root-zone soil under different potassium treatments (CK, T120, T180, T240, T300) across three growth stages. Panels (A–C) show differential abundance of rhizobacterial communities (LDA score >4) during seedling stage (A), tuberogenesis (B), and tuber expansion stage (C). Panels (D–F) display differential abundance of rhizofungal communities during seedling stage (D), tuberogenesis (E), and tuber expansion stage (F). Bar colors represent the specific potassium treatment where each taxon was significantly enriched, while bar length indicates the magnitude of differential abundance between treatments.

Figure 4

Potato yield in response to different potassium fertilizer application rates. Bars with different letters (a, b) indicate statistically significant differences (p<0.05). Error bars represent standard deviation.

Figure 5

Structural equation model showing relationships between potato yield, soil microbial diversity, and potassium fertilizer application. K fertilizers strongly increase potato production (0.98*, R²=0.98) while negatively affecting fungal diversity (r=-0.72*, p<0.05).