Abstract: Two straw returning treatments were set up (rotary tillage and ditch-buried returning straws were simulated by mixing the straws with and without soil, respectively) in a field plot experiment. Using the nylon mesh bag method, the decomposition characteristics of returning rice straws in both treatments were investigated under the applications of strawdecomposing microbial consortia and nutrient enhancement by measuring decomposition rates of straw and the contents of hemicellulose, cellulose, and lignin. The results showed that the decomposition rates of straw without soil were 4.5%-11.6% higher than those with soil in the first five months. On the  contrary, in the 12th month, the degradaton rates of straw with soil significantly increased by 4.9%-13.0% than those without soil. Straws in different treatments usually decomposed rapidly. More than 50% of mass was lost in the first two months, and then the decomposition fallen to a slow rate after two months. For the straws with soil, both applications of strawdecomposing microbial consortia and nutrient enhancement improved the efficiency of straw decomposition only in the first month, with the decomposition rates of straw being increased by 11.0% and 10.2% than that in the control (P<0.01), respectively. For the straws without soil, the microbial consortia significantly increased the efficiency of straw decomposition by 4.3%-9.7% compared with the control from one to five months, while the nutrient enhancement significantly increased it by 7.3%-14.4% from one to 12 months. The degradation rates of hemicellulose, cellulose, and lignin were 79.1%, 80.2% and 34.7% under the nutrient enhancement in the 5th month, respectively, which were not significantly different from that under the application of microbial consortia. In conclusion, both the microbial consortia and nutrient enhancement  could improve the decomposition efficiency of rice straw, and the treatment without soil was better than that with soil.

Key words: wheat, low temperature, hormone, antioxidative enzymes.