Despite the high phosphorus (P)-mobilizing capacity of legumes, little is known about the dynamics of the P fractions and bacterial communities in the rhizosphere of legumes in karst soils. A field experiment was established to investigate P uptake, rhizosphere P fractions and bacterial community structure of soybean (Glycine max (L.) Merr.) in response to P fertilization (0 and 90 kg P ha−1) in karst soils. Significant rhizosphere acidification was observed during soybean cultivation. Phosphorus fertilization further decreased soil pH, HCl-Pi and residual P, but increased NaHCO3-Pi in the rhizosphere of soybean variety YC03–3, which was associated with the simultaneous increase in P uptake and biomass. In addition, the bacterial community composition was significantly altered by P fertilization through its effects on soil pH and Ca. Bacillales and Pseudomonadales were the primary taxa influencing P dynamics, especially in soils without P input. Nevertheless, P fertilization decreased the relative abundance of Bacillales and Pseudomonadales, probably due to the enhanced rhizosphere acidification and improved P status. In karst soils, recalcitrant P can be depleted directly or transformed into more labile fractions by soybean rhizosphere acidification, even when P fertilizer is applied. As a consequence, P fertilization suppressed the growth of bacteria (Bacillales and Pseudomonadales) that contribute to P mobilization due to the reduced demands on these taxa to release P. Our findings highlight the importance of P fertilization in chemical P mobilization, which may consequently influence biological P turnover in the soybean rhizosphere.

中文翻译：

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磷肥对大豆根际磷动态和喀斯特土壤细菌群落的影响

尽管豆类具有高磷 (P) 动员能力，但对喀斯特土壤中豆类根际中 P 组分和细菌群落的动态知之甚少。建立了田间试验以研究大豆（Glycine max (L.) Merr.）对磷肥（0 和 90 kg P ha−1）在喀斯特土壤中的磷吸收、根际磷组分和细菌群落结构。在大豆栽培期间观察到显着的根际酸化。磷肥进一步降低了土壤 pH、HCl-Pi 和残留 P，但增加了大豆品种 YC03-3 根际的 NaHCO3-Pi，这与 P 吸收和生物量的同时增加有关。此外，磷肥通过对土壤 pH 值和 Ca 的影响显着改变了细菌群落组成。芽孢杆菌和假单胞菌是影响磷动态的主要分类群，尤其是在没有磷输入的土壤中。然而，施磷降低了芽孢杆菌和假单胞菌的相对丰度，这可能是由于根际酸化增强和磷状态改善。在岩溶土壤中，顽固的磷可以直接消耗或通过大豆根际酸化转化为更不稳定的部分，即使施用磷肥也是如此。因此，磷肥抑制了有助于磷动员的细菌（芽孢杆菌和假单胞菌属）的生长，因为这些分类群释放磷的需求减少。我们的研究结果强调了磷肥在化学磷动员中的重要性，这可能因此影响大豆根际生物磷周转。