Characterization of Biochar Prepared from Cotton Stalks as Efficient Inoculum Carriers for Bacillus subtilis SL-13

Biochar has the potential for use as a carrier of plant growth promoting rhizobacteria. The biochar in this experiment was produced by the pyrolysis of cotton stalks at high temperatures. Fourier transform infrared spectroscopy (FTIR) and an elemental analyzer characterized the structure and composition of the biochar, while scanning electron microscopy (SEM) observed the relationship between the bacteria and biochar. This study investigated the effects of biochar on the growth of Bacillus subtilis SL-13, a plant growth promoting rhizobacteria, as well as the adsorption of B. subtilis SL-13 to biochar under different conditions. The addition of biochar in a liquid nutrient broth medium was thought to promote the growth of B. subtilis SL-13 bacteria. The SEM images showed that the bacteria entered into the tubular structure of biochar. The adsorption of bacteria onto biochar increased with decreasing biochar particle size. The B. subtilis SL-13 population in biochar was maintained at 106 colony forming units g−1 (CFU) of biochar for up to 120 d. Therefore, the biochar could provide a beneficial microenvironment for the slow release and prolonged survival of bacteria as a carrier in future practical applications.