Reusing phosphate sludge enriched by phosphate solubilizing bacteria as biofertilizer: Growth promotion of Zea Mays

Phosphate sludge is considered as the main derivatives of the phosphate industry in Morocco, it is produced in huge quantities. Its management presents a big challenge for the phosphate industry. In this study phosphate solubilizing bacteria (PSB) were proposed as an innovative and ecological approach to solubilize phosphate sludge and promote plant growth. Four bacterial isolates (Pseudomonas Sp. DN 13-01, Sphingobacterium suaedae T47, Bacillus pimilus X22 and Bacillus cereus 263AG5) were selected as a potent PSBs. A bacterial consortium was formed with the four selected bacteria after checking their biocompatibility. The bacterial consortium has a great phosphate solubilization ability compared to that of single bacterial isolate. The four selected bacteria were also able to produce indole acetic acid, siderophores, hydrogen cyanide, H2S and CO2. The use of 40% of the phosphate sludge increases more the growth of Zea mays than the other proportions used. All the selected bacteria were able to increase significantly the Zea mays growth whatever the proportion of the phosphate sludge used, especially when they were inoculated as a consortium which increased much more the Zea mays growth. Also, the combination of the phosphate sludge amendment at 40% and the inoculation of the bacterial consortium gave the best yield of Zea Mays growth, where the plant height, fresh areal and root biomass were raised by 406.5%, 553 and 593 respectively compared to phosphorus poor soil. The use of Moroccan phosphate sludge combined with phosphates solubilizing bacteria is an important innovative and ecological approach to promote plant growth. It needs to be further studied to re-exploit the Moroccan phosphate sludge.