Physicochemical Properties and Bacterial Community Characteristics of Rhizosphere Soil in Olive Orchards under Different Soil Conditions

doi:10.13560/j.cnki.biotech.bull.1985.2025-0755

Abstract

Abstract:

Objective To provide a basis for optimizing cultivation techniques, this study explored the effects of different soil conditions (loess, phyllite soil, and debris flow alluvial fan soil) in the non-traditional olive-growing area of Longnan, Gansu on the rhizosphere microorganisms of olive trees. Method The study focused on 15-year-old ‘Lei Xing’ olive trees in Wudu district, Longnan. Soil physical and chemical properties were measured, and the bacterial community structure and function were analyzed through metagenomic sequencing. Result All three soil types showed slightly alkaline pH (7.87-7.93). Debris flow alluvial fan soil (Cs) possessed significantly higher levels of key nutrients compared to loess (As) and schist (Bs) soils, including available nitrogen (AN: 186.03 mg/kg), total phosphorus (TP: 2.23 g/kg), and soil organic matter (SOM: 64.58 g/kg).Actinobacteria and Proteobacteria were the dominant bacterial phyla in both the rhizosphere and root endosphere compartments across all soil types. The relative abundance of Actinobacteria was significantly elevated in the Cs rhizosphere soil. PCA revealed that root endosphere microbial communities were relatively similar regardless of soil type. In contrast, rhizosphere microbial communities from Bs and Cs soils clustered together, showing significant divergence from those in As soil. RDA indicated that soil pH, total nitrogen (TN), total phosphorus (TP), and organic matter (OM) were the primary environmental factors driving variation in microbial community composition, collectively explaining 99.28% of the observed variance. Notably, the relative abundance of Actinobacteria showed a significantly positive correlation with TN, TP, and OM contents. KEGG annotation demonstrated that metabolic functions dominated the functional profiles across all samples. Metagenomic analysis further revealed a higher abundance of genes associated with nitrogen cycling pathways in the Cs rhizosphere soil compared to the other soil types. Conclusion This study demonstrates that soil type significantly shapes the structure and functional potential of olive rhizosphere microbial communities in the non-traditional Longnan region, primarily through its influence on nutrient availability and pH. Debris flow alluvial fan soil (Cs), characterized by higher nutrient content and a suitable pH, fostered a distinct and potentially beneficial microbial community enriched in Actinobacteria. Consequently, Cs soil should be prioritized as a reference soil type for new olive orchard site selection in similar non-traditional regions. These findings provide a scientific basis for enhancing olive cultivation efficiency through optimized soil management and site selection.

Key words: olive garden, rhizosphere soil, physicochemical properties, metagenomics, bacterial community

ZHANG Jian-xia, JIANG Cheng-ying, WU Wen-jun, JIN Gao-ming, ZHANG Cong-cong, YAO Yu-fang, ZHANG Rong, QI Jian-li. Physicochemical Properties and Bacterial Community Characteristics of Rhizosphere Soil in Olive Orchards under Different Soil Conditions[J]. Biotechnology Bulletin, 2026, 42(4): 287-296.

Figures/Tables 7

Fig. 1 Microbial community composition at the phylum (a) and genus (b) levels in the rhizosphere soil of olive orchards under different soil conditions

Table 1 Statistical summary of soil physicochemical properties for olive trees

类型Type

速效氮

AN（mg/kg）

全氮

TN（mg/g）

速效磷

AP（mg/kg）

全磷

TP（g/kg）

全钾

TK（g/kg）

速效钾

AK（mg/kg）

有机质

OM（g/kg）

Fig. 2 Principal component analysis (PCA) of microbial communities at the phylum (A) and genus (B) levels in the rhizosphere soil of olive orchards under different soil conditions

Fig. 3 LEfSe analysis of soil bacteria in different olive orchardsThe circles from the outermost to the innermost refer tothe taxonomic levels of phylum, class, order, family, and genus, respectively. The colored dots indicate important fungal groups within each category, while the yellow dots denotefungal groups that do not show significant differences in abundance across the groups

Fig. 4 Redundancy analysis of the top 10 most abundant bacterial genera in the rhizosphere soil of olive trees and environmental factors

Fig. 6 Functional composition of rhizosphere soil microorganisms in olive orchards under different soil conditions at level 1 (A), level 2 (B) and level 3(C) functional categories

Fig. 7 Correlation between soil environmental factors and key microbial functions in the rhizosphere of olive trees (KEGG)

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