Effects Of Rice Straw And Aluminum Sulfate Application On The Quantity And Composition Of Soil Organic Matter In Soda Saline-alkaline Soil

Soda saline-alkaline soil is considered as one of the most potential soil resource in the western of Jili Province, and is also hardest soil type to improve. Through the tireless efforts of several generations of scientists, a set of improvement measures of rice planting oriented and aluminum sulfate application has now formed. Promoting effect of aluminum sulfate on the content of soil organic matter was found in the production practice. The soda meadow solonetzs in Songnen plains were sampled to conduct the waterlogged laboratory incubation experiment. The effects of aluminum sulfate and rice straw on changes in organic carbon content, humus composition, labile organic carbon content, organo-mineral complex were investigated, and the effects of aluminum sulfate and rice straw on the quality and composition of organic matter were further discussed in order to provide the theory basis for the technology system establishment of rapid improvement and fertilizer of newly exploited paddy in Songnen plains. The results of the study summarized as follows:1. Rice straw and aluminum sulfate were conducive to increase the content of soil organic carbon. For the treatments with same amount of aluminum sulfate application, soil organic contents increased with the increased of the amount of rice straw. For the treatments with the same amount of rice straw application, soil organic contents increased with the increased of the amount of aluminum sulfate application. For the treatment with high amount of rice straw application, all treatments had significant difference.2. The contents of free form, combined form of humus and their compositions(humic acid and fulvic acid) were increased at different levels with rice straw application. Especially, the increase of free form of humus was more significantly. Aluminum sulfate application significantly increased the content of free form of humus and humic acid, and decreased the content of combined form of humus and humic acid. Aluminum sulfate application made part of free form of humus and humic acid into combined form of humus and humic acid, and this transformation had positive correlation with the application amount of aluminum sulfate.3. Both of rice straw and aluminum sulfate applications could decrease the humification degree of free form and combined form of humic acid. The type of free form of humic acid changed to P type after rice straw applied. Aluminum sulfate applying promoted the type of free form of humic acid changed from P type to Rp type, and this promoting effect was related to the amount of rice straw application. For rice straw application, each type of combined form of humic acid just changed in the distribution areas of A type, and not transferred into other areas and became other types. Aluminum sulfate had no significantly effect on type of combined form of humic acid. According to the types of humic acid, it could be concluded that humic acid became younger and renewed after applying of rice straw and aluminum sulfate.4. Soil microbial biomass carbon, microbial quotient increased by108.5%~310.3% and 76.1%~178.3%, respectively, after rice straw applied. Low level of rice straw application was more conducive to the increase of soil microbial biomass carbon and microbial quotient. Aluminum sulfate could further promote the increase of soil microbial biomass carbon. Furthermore, the amount of aluminum sulfate had positive correlation with the content of microbial biomass carbon. For the treatments without rice straw, aluminum sulfate could increase the content of easily oxidized organic carbon, and decrease the value of Kos. Both of rice straw and aluminum sulfate application could increase easily oxidized at different levels. The value of Kos increased firstly, and then decreased, along with the aluminum sulfate increasing.5. Rice straw application promoted small size fraction of complex agglomerate to large one, at the same time increased organic carbon content of the different size fractions of complexes. Aluminum sulfate application promoted organic colloid produced from straw decomposition and inorganic particles form organo-mineral complexes, and promoted the aggregation of soil, increased the organic carbon content of large fraction of organo- mineral complexes.