Comparison of the Effect of NaOH Pretreatment and Microbial Agents on Rice Straw Decomposition

Abstract

Rice straw contains a large amount of lignocellulose which is difficult to be decomposed. The objective of this study was to determine the effect of alkaline pretreatment (sodium hydroxide, NaOH) and microbial agents on the decomposition of rice straw. The experimental detail consisted of NaOH (control and NaOH solution pretreatment) and microbial agent (Bacillus licheniformis agent, Bacillus subtilis agent, Trichoderma viride agent, and no microbial agent) treatments. Compared with no NaOH pretreatment, the pH of NaOH pretreatment increased by 6.30–18.28%, while the electrical conductivity decreased by 49.18%, but the change in total nutrient content was not obvious. Under no NaOH pretreatment, Bacillus subtilis agent improved the temperature of the rice straw decomposition. Compared with Bacillus licheniformis agent and Trichoderma viride agent, Bacillus subtilis agent increased the alkali-hydrolyzable nitrogen, available phosphorus, and available potassium in rice straw by 1.39–10.30%. The organic carbon content was reduced by 3.50% and 17.15%. The germination index was greater than 80%. Under NaOH pretreatment, the pile with Bacillus subtilis agent reached the maximum temperature (39.5 °C) on the 12th day. Compared with Bacillus licheniformis agent and Trichoderma viride agent, Bacillus subtilis agent increased the content of alkali-hydrolyzable nitrogen and available phosphorus in rice straw by 1.64–11.87%. The humus polymerization, organic carbon, and carbon/nitrogen ratio were reduced by 6.40–44.06%. In addition, gray analysis, principal component analysis, and comprehensive evaluation were used to comprehensively evaluate the effect of straw decomposition. The results showed that Bacillus subtilis agent under NaOH pretreatment and no NaOH pretreatment had the most obvious effect on rice straw composting. This study provides a scientific basis for efficient decomposition of rice straw.