Effect of K-Solubilizing Purple Nonsulfur Bacteria on Soil K Content, Plant K Uptake, and Yield of Hybrid Maize Grown on Alluvial Soil in a Dyke Area in Field Conditions

Microorganisms are considered a potential source of biofertilizers for mobilizing nutrients from insoluble mineral potassium (K). This study was conducted to evaluate the effects of liquid potassium-solubilizing bacteria, Cereibacter sphaeroides M-Sl-09, Rhodopseudomonas thermotolerans M-So-11, and Rhodopseudomonas palustris M-So-14 (LPS-PNSB), on soil K content, plant K uptake, growth, and yield of hybrid maize cultivated on alluvial soil in the dyke-protected area of An Phu, An Giang, Vietnam. Results showed that the application of LPS-PNSB significantly improved exchangeable soil K from 0.428 to 0.460–0.470 meq 100 g−1, total plant K uptake from 181.5 to 205.8–259.4 kg ha−1, and yield from 11.1 to 12.2–12.6 ton ha−1, compared with the recommended 100% NPK fertilization. The addition of LPS-PNSB allowed a 100% reduction in K fertilizer compared with the recommended rate while still maintaining yield. Hybrid maize grain yield further increased when 100% recommended K was applied in combination with LPS-PNSB, surpassing the yield obtained with 100% K alone.