Potassium-Solubilizing Endophytic Bacillus albus Strain NVC-BL3 and Its Effects on Baby Maize Productivity Under Reduced Potassium Fertilization

Potassium (K) deficiency and inefficient fertilizer use constrain sustainable maize production, highlighting the need for biological strategies to improve soil K availability. This study evaluated the potassium-solubilizing capacity of Bacillus albus strain NVC-BL3 and its effects on baby maize productivity under different KCl application rates. B. albus strain NVC-BL3 was identified using 16S rRNA gene sequencing and assessed for K solubilization using K-feldspar. Soluble K increased from 8.2 mg L−1 at inoculation to approximately 309 mg L−1 after 7 days, demonstrating substantial mineral-K solubilization under laboratory conditions. A field experiment was conducted using a 2 × 4 factorial randomized complete block design with bacterial inoculation and four KCl application rates (0, 40, 60, and 80 kg ha−1). Inoculation increased soil total nitrogen, available phosphorus, and exchangeable potassium, as well as plant height, leaf development, and chlorophyll content. Compared with uninoculated treatments, B. albus strain NVC-BL3 inoculation increased ear number, fresh ear weight, cob weight, and aboveground biomass by 3.2%, 3.0%, 5.5%, and 3.5%, respectively. Increasing KCl application also improved crop performance; fresh ear weight and cob weight at 60 kg KCl ha−1 were statistically comparable to those at 80 kg KCl ha−1. Inoculation also increased edible cob lipid, phosphorus, and potassium concentrations by 6.8%, 4.5%, and 5.0%, respectively. Significant inoculation × KCl interactions were detected for fresh ear weight, cob weight, and aboveground biomass, indicating that responses to KCl application depended on inoculation status for these traits. Overall, B. albus strain NVC-BL3 demonstrated mineral-K-solubilizing potential and modest improvements in soil properties, baby maize productivity, and nutritional quality. The results identify 60 kg KCl ha−1 as a potentially useful reduced application rate under the conditions tested; however, the specific contribution of bacterial inoculation to the response at this rate requires treatment-level comparisons and further field validation.