Molecular Soil Biology 2026, Vol.17, No.1, 26-37 http://bioscipublisher.com/index.php/msb 27 Phosphate-respiring bacteria (also referred to as phosphate-respiring microorganisms in a broad sense) transform difficult-to-utilize phosphorus into absorbable forms through processes such as organic acid solubilization of phosphorus, enzymatic mineralization, and metal chelation. They are considered as potential approaches to enhance crop phosphorus nutrition and reduce reliance on chemical phosphorus fertilizers (Adeyemo et al., 2025). At the functional gene level, phoD (related to alkaline phosphatase) is widely distributed in the soil and can serve as an important marker for characterizing the potential of organic phosphorus mineralization; while gcd and its related pqq gene cluster are closely related to the glucose dehydrogenase-glutaric acid pathway and are key links in the typical inorganic phosphorus dissolution mechanism (Chen et al., 2024). For acidic tea gardens, the core scientific issues have gradually focused on: whether phosphate-respiring bacteria can "stably perform" under the background of strong acid and aluminum-rich iron, how the community is constructed and maintained, whether there is functional redundancy, and the long-term impact of agent input on the local microbial network and ecological security (Wan et al., 2025). 2 Soil Characteristics of Acidic Tea Gardens and the Limiting Mechanism Of Phosphorus Availability 2.1 Phosphorus fixation and precipitation mechanism under acidic conditions In acidic soil, the availability of phosphorus is constrained by the "surface adsorption-mineral precipitation" dual process: On one hand, phosphate ions are easily adsorbed on the surfaces of minerals with positive charges or strong coordination sites (such as Fe/Al oxides), reducing the concentration of phosphorus available for plant absorption in the soil solution; on the other hand, phosphorus can also form insoluble mineral phases with Fe and Al, or undergo co-precipitation in the microenvironment, thus entering more stable and less-released reservoirs (Jindo et al., 2023). The rhizosphere processes (root absorption, proton release, organic acid secretion) and microbial metabolism will change the local pH and ligand supply, thereby affecting the adsorption/desorption and dissolution/precipitation equilibrium (Pang et al., 2024). Therefore, the phosphorus limitation in "acidic tea gardens" is not a static deficiency but is continuously locked by geochemical processes (Yigezu et al., 2023; Pizon et al., 2025). 2.2 The effects of aluminum and iron ions on the availability of phosphorus Aluminum and iron are the key active components that affect the availability of phosphorus in acidic soils: At low pH conditions, exchangeable Al^3+ is more likely to be released and participate in phosphorus fixation, transferring phosphorus from the available pool to the unavailable pool; at the same time, aluminum toxicity also interferes with the absorption, transportation, and utilization of various nutrients (including phosphorus) by plants. From the microbial perspective, acidity and soluble/exchangeable aluminum may inhibit the activity of some soil enzymes (including the acidic phosphatase activity related to the phosphorus cycle) and change microbial growth and substrate utilization, thereby indirectly affecting organic phosphorus mineralization (Pang et al., 2024; Wang et al., 2025). Given that tea plants have strong aluminum tolerance and enrichment characteristics, the coupling relationship of "aluminum-microorganisms-phosphorus" in tea garden ecosystems is more complex: On one hand, aluminum promotes phosphorus fixation; on the other hand, the organic ligands released by plants and microorganisms may chelate aluminum and promote local phosphorus release (Guo et al., 2024; Scherwietes et al., 2025). 2.3 Synergistic effect of long-term fertilization in tea gardens and soil acidification Tea gardens often apply high nitrogen intensities to enhance yield and quality. The processes such as ammonium nitrogen nitrification generating protons and nitrate nitrogen leaching carrying basic ions accelerate soil acidification. Moreover, acidification enhances the activation of Al and the fixation of phosphorus, further exacerbating the "high input-low utilization" problem of phosphorus efficiency. National-scale surveys and long-term field studies have all indicated that soil acidification in tea gardens is widespread in most production areas, and the fertilizer management method is an important driving factor (Figure 1) (Shu et al., 2025). Further, long-term nitrogen addition can reduce soil available phosphorus and induce changes in microbial communities and functional genes related to phosphorus cycling, demonstrating a chain effect of "nitrogen-driven acidification-acidification-driven phosphorus limitation-microbial response reshaping phosphorus cycling".
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