Interaction effect of Bacillus subtilis co-inoculation and mine water irrigation on cowpea's growth, physiology and nutritional quality

This study evaluated the interaction of Bacillus subtilis (BD233) co-inoculation and mine water (75% MW) irrigation on the growth, nodulation, physiology and nutritional quality of cowpea. Three cowpea genotypes were exposed to four treatments namely i) Co-inoculation with B. subtilis (B+) and irrigation with 75% MW, ii) Co-inoculation with B. subtilis (B+) and tap water irrigation (0% MW), iii) No B. subtilis co-inoculation (B-) and irrigation with 75% MW and iv) No co-inoculation with B. subtilis (B-) and irrigation with tap water (0% MW) (control). A factorial experiment was repeated once in a glasshouse using a randomized complete block design with five replications. The results showed that at 125 DAP, Nyira and Asetanapa, not co-inoculated with B. subtilis (B-) and irrigated with 0% MW showed significantly higher number of branches per plant whilst Soronko irrigated with 0% MW but co-inoculated with B. subtilis (B+) had the tallest plants with a corresponding higher biomass compared to the other treatments. With 0% MW irrigation, Soronko and Nyira co-inoculated with B. subtilis (B+) had the highest nodule counts, plant pod counts, pod fresh weight, pod dry weight, number of seeds and seeds fresh weight per plant compared to Asetenapa and control. Co-inoculation with B. subtilis affected heavy metals (Ca, Fe, Zn, Mn & Al) accumulation in shoot and grain of the tested cowpea genotypes. These findings clearly suggest that B. subtilis has ability to sequester heavy metals in soils polluted with mine water and also enhance the growth, nodulation and yield of an important economic crop.