Microorganisms release nutrients from minerals. However, this process is not yet well understood despite its importance for soil fertility. The aim of this study was to determine which factors control microbial phosphorus (P) and silicon (Si) release from apatite and weathered rock, and to analyze which microbial-mediated processes cause P and Si solubilization. For this purpose, we conducted a series of incubation experiments with apatite and saprolite (weathered bedrock) and soil extracts of four soils that are located along a climate gradient in the Coastal Cordillera of Chile and differ in soil P fractions and degree of weathering. We developed an approach that allowed us to measure the release of P from apatite and the release of Si from saprolite by microbial consortia in soil solution. The microbial consortia of all soil extracts caused release of P from apatite. The addition of carbon (C) and nitrogen (N) to the soil solution increased the rate of microbial P solubilization from apatite by a factor of about 10 in all soil depth increments. The pH decreased strongly during the incubations. In the depth increments 0.1–0.2 and 0.4–0.6 m, the P solubilization rates were negatively correlated with the pH measured at the end of the incubation (r² = 0.55 and 0.76, respectively, both p < 0.01). Nine organic acids were detected throughout the experiment. The total concentration of carboxyl groups was positively correlated with the P solubilization rate (r² = 0.94, p < 0.01). The addition of dissolved inorganic P to the soil extracts did not significantly decrease the P solubilization rates. The rate of microbial Si solubilization from saprolite increased strongly with the surface area of the saprolite. We conclude that microbial solubilization of P from apatite was limited by the availability of easily decomposable C and that microbial solubilization of P from apatite was not affected by P availability, indicating that this process is not or not exclusively controlled by microbial need for P. In conclusion, our results indicate that microbial weathering of minerals in saprolite is strongly constrained by the availability of organic C and by the specific surface area of the saprolite.

微生物从矿物质中释放出营养。然而，尽管该过程对土壤肥力很重要，但尚未得到很好的理解。这项研究的目的是确定哪些因素控制着磷灰石和风化岩石中微生物磷（P）和硅（Si）的释放，并分析了哪些微生物介导的过程导致P和Si溶解。为此，我们用磷灰石和腐泥土（风化的基岩）以及沿智利沿海科迪勒拉气候梯度分布的四种土壤的土壤提取物进行了一系列孵化实验，土壤磷含量和风化程度不同。我们开发了一种方法，该方法使我们能够测量土壤溶液中微生物群落对磷灰石中磷从磷灰石中的释放以及硅从腐泥土中的硅的释放。所有土壤提取物的微生物群落都会导致磷灰石中磷的释放。在所有土壤深度增量中，向土壤溶液中添加碳（C）和氮（N）可使磷灰石对微生物P的溶解速率增加约10倍。在孵育过程中，pH值急剧下降。在深度增量0.1–0.2和0.4–0.6 m中，磷的增溶速率与孵育结束时测得的pH呈负相关（r^2分别 为0.55和0.76，均p <0.01）。在整个实验过程中检测到九种有机酸。羧基的总浓度与磷的增溶速率呈正相关（r ² = 0.94，p <0.01）。向土壤提取物中添加溶解的无机P不会显着降低P的增溶速率。腐泥土中微生物溶解硅的速率随腐泥土表面积的增加而大大增加。我们得出的结论是，磷从磷灰石的微生物增溶作用受到易分解C的可用性的限制，磷从磷灰石的磷增溶作用不受磷的可用性的影响，这表明该过程不受或不受磷对磷的微生物需求的唯一控制。总之，我们的结果表明，腐泥土中矿物的微生物风化受到有机碳的可用性和腐泥土比表面积的强烈限制。