The purpose of this study is to improve relative phosphorus (P) distribution in various proportions by greater solubility in the rhizosphere of plants influenced by phosphate solubilizing bacteria (PSB), P availability, and fertilizer management. For this purpose, a pot experiment was conducted with three phosphorus concentrations including 0 (P0), 20.5 (P50), and 41 (P100) mg P kg−1 and two PSB strains as well as Enterobacter cloacae R13 (R13) and E. cloacae R33 (R33) as factors which were evaluated at three harvesting times: 60, 95, and 140 days after planting (DAP) sowing. In the non-fertilized condition, treatments inoculated by R13 and R33 had higher P uptake in comparison with the non-inoculated treatment. Compared with the bulk soil, the chemical composition of the soil solution sample was affected by the dynamic properties of rhizosphere. In the inoculation-treated rhizosphere, the soluble P concentration was higher than that in the non-inoculated treatment. However, P uptake was greater in the inoculated treatments. Also, higher P free ions (H2PO4− and HPO42−) activity and lower calcium (Ca2+) and magnesium (Mg2+) activity were observed in soil solution inoculated rhizosphere as compared with the non-inoculated treatment. At all harvesting times, octacalcium and β-tricalcium phosphate minerals controlled P concentration in the rhizosphere. The pedogenic Ca-P or low soluble P (Ca8-P) was higher by up to 72.97% compared with other fractions, which can be ascribed to octacalcium and β-tricalcium phosphate minerals. In the current study, we conclude that the reduction of pH is not a major mechanism in dissolving insoluble P by E. cloacae although phosphate solubility may be attributed to the chelation process. In comparison, rhizosphere characteristics were more effective than PSB in converting the type of P-containing minerals. The results suggest that Ca8-P fraction is equivalent to octacalcium phosphate and β-tricalcium phosphate minerals in the rhizosphere of sugarcane.

中文翻译：

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甘蔗(Saccharum officinarum L.)根际受阴沟肠杆菌影响的磷的形态和分馏

本研究的目的是通过在植物根际中更大的溶解度来改善不同比例的相对磷 (P) 分布，这些溶解度受磷酸盐增溶细菌 (PSB)、磷的有效性和肥料管理的影响。为此，使用三种磷浓度进行了盆栽实验，包括 0 (P0)、20.5 (P50) 和 41 (P100) mg P kg-1 和两个 PSB 菌株以及阴沟肠杆菌 R13 (R13) 和大肠杆菌。 cloacae R33 (R33) 作为在三个收获时间评估的因素：种植后 (DAP) 播种后 60、95 和 140 天。在未施肥条件下，与未接种处理相比，接种 R13 和 R33 的处理具有更高的磷吸收。与散装土壤相比，土壤溶液样品的化学成分受根际动态特性的影响。接种处理的根际可溶性磷浓度高于未接种处理。然而，在接种处理中磷的吸收更大。此外，与未接种处理相比，在土壤溶液接种根际观察到更高的 P 游离离子（H2PO4- 和 HPO42-）活性和更低的钙（Ca2+）和镁（Mg2+）活性。在所有收获时间，八钙和 β-磷酸三钙矿物质控制根际 P 浓度。与其他组分相比，成土的 Ca-P 或低可溶性 P（Ca8-P）高达 72.97%，这可以归因于八钙和 β-磷酸三钙矿物。在目前的研究中，我们得出结论，pH 值的降低不是大肠杆菌溶解不溶性 P 的主要机制。尽管磷酸盐的溶解度可能归因于螯合过程。相比之下，根际特征在转化含磷矿物类型方面比 PSB 更有效。结果表明Ca8-P组分相当于甘蔗根际中的磷酸八钙和β-磷酸三钙矿物。