Effect of Potassium Solubilizing Bacteria and Humic Acid on Faba Bean (Vicia faba L.) Plants Grown on Sandy Loam Soils

Abstract

Potassium use efficiency (KUE) in faba bean production is often low, and the luxury of fertilization has negative environmental impacts. The current study aims to reduce the recommended dose of potassium (K) for faba bean by potassium solubilizing bacteria (PSB) and humic acid (HA). The studied treatments were 50 and 100% of K recommended dose with or without PSB and 40 kg of HA ha−1. The studied treatments were applied to faba bean ((Vicia faba L., cv. Giza 843) plants grown in sandy loam soils for two successive seasons. In this study, the maximum KUE (40%) was obtained in the soil treated with HA and PSB while the lowest one (14%) was found in the case of the full recommended dose of mineral form. Humic acid and PSB that were applied to the plants fertilized with 50% of the recommended dose gave the maximum growth and yield. Humic acid and PSB increased the soil cation exchange capacity (CEC) by 6% and the soil organic matter (SOM) by 12%. Chlorophyll and carbohydrates in the leaves were increased by 36 and 50%, respectively, above the control, as results of HA and PSB application. Adding half of K requirements for faba bean in a mineral form with 40 kg of HA and PSB led to 14% and 19% increases in the seed and straw yield compared to the full mineral fertilization without bacterial inoculation. Humic acid and potassium solubilizing bacteria can be used to improve soil quality and increase the availability and uptake of nutrients, and thus increase the yield of faba bean plants. The experimental results from our 2-year research on faba bean grown on sandy loam soils establish a deductive scientific basis for using bio-fertilizers and organic materials to produce cleaner food and better environment conditions.