Decomposing Characteristics Of Main Crop Straws In Guangxi

In order to provide a scientific basis for the rational utilization of straw and nutrient resource management, this study has investigated the decomposition rate, nutrient release characteristic, microbial quantity and enzyme activity in the decomposing process for different straw treatments. There were two kinds of rice straw (low N and high N), sugarcane leaf and cassava stalk, treated with original, chopped, chopped with decomposer and chopped with farm manure using the nylon net～bag method under the outdoor condition. Dry matter mass, nutrient content, microbial quantity and enzyme activity were determinated at0,10,28,35,51,74and91d after treatment for rice straw experiment, and at0,27,60,102,141,195,233,269and304d after treatment for the experiments of sugarcane leaf and cassava stalk, respectively. The main results are outlined as follows:(1) Decomposing and nutrient releasing strength of rice straw were the largest at the first10days, at91d after the decomposition, the decomposing rate of rice straw was60.2-73.8%, the order of nutrient release rate was K>P>N. The treatments of chopped straw, chopped straw with decomposer or farm manure could promote the quantity of bacteria, and improved the activities of phosphatase and catalase, thereby promoted the straw decomposing and nutrient release, the treatment of chopped rice straw with farm manure was the best. The difference of decomposing and nutrient releasing rate in low N and high N straws was not significant, but the decomposing strength and nutrient releasing strength in high N straw were higher than those of low N straw.(2) The decomposing strength in sugarcane leaves was the largest at27-60d, and the releasing strength of K was the largest at0-27d. The decomposing rate and release rates of N, P and K in sugarcane leaves were46.02-55.12%,48.3-64.05%,40.11-58.67%and84.95-88.52%. Chopped leaves increased microbial quantity and improved the activities of phosphatase, urease and catalase, thereby promoted the decomposing and nutrient releasing. Chopped leaves with exogenous bacteria agent further increased the quantity of actinomyces and fungi and activities of urease and catalase, thereby further promoted the K and P releasing, and the treatment of chopped leaves with farm manure was the best.(3) The decomposing strength in cassava stem was the largest at27-60d, and releasing strength of N and K was the largest at0-27d. The decomposing rate and releasing rates of N, P and K in cassava stem were59.33-～67.59%,31.94-54.55%,30.55-47.72%and93.75-96.02%. Chopped stem increased the quantity of bacteria and actinomyces and the enzyme activity, thereby promoted the decomposing and N and K releasing in cassava stem in the first141days. Chopped stem with exogenous bacteria agent further increased microbial quantity and the activities of phosphatase and invertase, thereby further promoted stem decomposing and N and K releasing in the first60days, and the treatment of chopped stem with decomposer was the best. Chopped stem with exogenous bacteria agent promoted the release of K at27-60d.Therefore, chopped straw promoted the decomposing and nutrient releasing; chopped straw with exogenous bacteria agent further increased decomposing and nutrient releasing.