Potential effects of biochar-based microbial inoculants in agriculture

Biochar has been used widely as a soil amendment to improve plant growth, nutrient acquisition, stress tolerance and to improve soil biological, chemical and physical properties. Several studies suggest biochar as a carrier for bacterial inoculants under various climatic and environmental conditions because of the properties that favour microbial life. Biochar is rich in organic carbon, contains nutrients, such as N, P, K, has a high porosity, and high water-holding capacity. In this review, we synthesise results on the effectiveness of biochar as a carrier for inoculum in pot and field conditions. Biochar as a carrier supported a high survival rate of introduced bacteria and significantly increased colonization in the plant rhizosphere. Soil microbes are known to play an essential role in soil biochemical processes, and nutrient cycles; improve plant stress tolerance, and nutrient acquisition through their ability to fix atmospheric nitrogen, solubilize phosphate, or by enhancing decomposition of plant residues. Moreover, biochar-based inoculants increased root and shoot biomass, nodulation and nutrient uptake of plants in pot and field experiments. Biochar-based inoculants were also effective in enhancing plant growth and grain yield in pot and field experiments. These studies demonstrate that biochar can be considered as a suitable carrier or formulation of bacterial inoculants even in hostile environments and might contribute to replace other commercially used materials successfully. Biochar-based rhizobial inoculants can significantly improve the symbiotic performance of legumes with rhizobia which may reduce N fertilizer demand and thus promote the sustainability of crop production.