Chemical potassium (K) fertilizer is commonly used in apple (Malus domestica L. Borkh) production but K is easily fixed by soil, resulting in reduced K fertilizer utilization and wasted resources. K-solubilizing bacteria (KSB) can cost-effectively increase the soluble K content in rhizosphere soil. Therefore, the objectives were to select high-efficiency KSB from apple orchards under various soil management models and evaluate their effects on apple seedling growth. Maize (Zea mays L.) straw mulching (MSM) increased the total carbon (TC), total nitrogen (TN) and available potassium (AK) in the rhizosphere and improved fruit quality. The number of KSB in the rhizosphere soil of MSM was 9.5×10⁴ CFU g⁻¹ soil, which was considerably higher than that in the other mulching models. Fourteen KSB strains were isolated with relative K solubilizing ability ranging from 17 to 30%, and five strains increased the dry weight per apple seedling. The most efficient strain was identified as Paenibacillus mucilaginosus through morphological observation and sequence analysis of 16S rDNA, named JGK. After inoculation, the colonization of JGK in soil decreased from 4.0 to 1.5×10⁹ CFU g⁻¹ soil within 28 d. The growth of the apple seedlings and the K accumulation in apple plants were promoted by irrigation with 50 mL JGK bacterial solution (1×10⁹ CFU mL⁻¹), but there was no significant increase in the AK content of rhizosphere soil. High-performance liquid phase analysis (HPLC) data showed that the JGK metabolites contained phytohormones and organic acids. Hence, the JGK strain promoted the growth of two-month-old apple seedlings by stimulating function of the produced phytohormones and enhanced K solubility by acidification for apple seedling uptake. This study enriches the understanding of KSB and provides an effective means to increase the K utilization efficiency of apple production.

化学钾（K）肥料通常用于苹果（Malus domestica L. Borkh）生产中，但钾很容易被土壤固定，导致钾肥利用率降低和资源浪费。增钾细菌（KSB）可以经济有效地增加根际土壤中的可溶性钾含量。因此，目的是在各种土壤管理模式下从苹果园中选择高效KSB，并评估其对苹果幼苗生长的影响。玉米（Zea mays L.）秸秆覆盖（MSM）增加了根际的总碳（TC），总氮（TN）和有效钾（AK），并改善了果实品质。MSM根际土壤中的KSB数为9.5×10 ⁴ CFU g ^-1土壤，这大大高于其他覆盖模型。分离出14种KSB菌株，其相对K增溶能力为17％至30％，其中5种菌株增加了每株苹果幼苗的干重。通过对16S rDNA的形态学观察和序列分析，鉴定出最有效的菌株为粘膜芽孢杆菌，命名为JGK。接种后，在28 d内，JGK在土壤中的定殖从4.0下降到1.5×10 ⁹ CFU g ^-1土壤。通过50 mL JGK细菌溶液（1×10 ⁹ CFU mL ^-1）灌溉促进苹果幼苗的生长和钾在植物中的积累。），但根际土壤AK含量没有显着增加。高效液相分析（HPLC）数据表明，JGK代谢产物含有植物激素和有机酸。因此，JGK菌株通过刺激产生的植物激素的功能促进了两个月大的苹果幼苗的生长，并通过酸化提高了钾的溶解度，从而促进了苹果幼苗的吸收。该研究丰富了对KSB的认识，为提高苹果生产中钾素利用效率提供了有效手段。