Effect of corn straw biochar on corn straw composting by affecting effective bacterial community

This study investigated the effect of corn straw biochar on the decomposition, nutrient transformation, and bacterial community characteristics in the corn straw decomposition process. A 90-day microcosm incubation experiment was performed to assess the effects of corn straw biochar (500 °C, 1 h) on the corn straw decomposition process and the resulting product. Four biochar amendment rates (0%, 5, 10, and 15%, as mass fractions of biochar) and three different addition times (1st day, 30th day, and 60th day) were set in total. The results showed that corn straw biochar significantly increased the pH of the corn straw decomposition process by 0.71–0.73 and increased the electrical conductivity value by 0.64–1.07 μS/cm over that of the controls. In addition, biochar was shown to increase the temperature rise rate and temperature peak of the straw maturation system, and advance the process of straw maturation by 10 days. Thus, treatment with corn straw biochar could accelerate the corn straw decomposition process and change the conditions for microorganisms involved in the process. Furthermore, biochar additions significantly decreased the organic matter content by 9.67% under B3 and T1 treatment, and enhanced the N, P2O5, and K2O contents of the straw decomposition product by 0.36, 0.19, and 0.88% under B3 and T1 treatment. Biochar additions could increase the abundance of several effective bacteria closely related to the N, P2O5, and K2O contents of the straw maturation product. The growth of these bacteria was likely to be affected by the increase in pH with biochar addition, which enabled the improvement of the nutrient mineralization process.