| Fluvor-aquic soil is the most widely distributed and the largest farming soil in Huanghuaihai Plain,which is an important major grain producing area.Saline-alkali harms and low organic matter content are the two major factors that restrict crop yield in fluvor-aquic soil area.This study was based on soil increase long-term test platform and included three different soil texture(sand,loam and clay).The main research purposes were as follows:(1)The available soil nutrients,soluble nitrogen and carbon functional group,enzyme activity and microbial content was determined to clear the commonness and characteristics of different soil texture.(2)The influence of different texture soils on straw was cleared through the reserch of wheat and maize straw decomposition,the change of nutrient content,microorganism quantity and community.(3)The different microbial populations position,community structure were studied to clear the effects of the distance of the decomposition straw on microorganisms and then to infer the main microbial straw decomposition.The results were as follows:(1)Six months later,there were no significant differences in nitrate content in different soil texture.Ammonium and potassium concentrations were expressed as clay>loam>sand.The content of ammonium nitrogen in clay was exceeding that in loam and sand by 46.16?50.94%.The content of available K in clay was exceeding that in loam and sand by 104.40?218.37%.Clay phosphorus content was significantly lower than that in loam and sand.There were no significant differences in the content of DOC among the three soils.The content of DON in clay and loam soil were significantly higher than that in sandy soil,while the content of aromatic functional groups was lower.The content of cellulase enzymes and phosphatases in the clay were higher than those in sandy soil.(2)Based on PLFA analysis,there was a significant difference in bacteria PLFA,fungi PLFA and the total PLFA among the three soil textures,with the highest contents in clay soil and the lowest content in sandy soil basically.There were no significant differences in gram positive bacteria/gram negative bacteria and cyc PLFA/normal saturated PLFA,but fungi/bacteria and monounsaturated fatty acids/branched fatty acids ratio were higher in the clay soil.Different soil texture significantly differed from each other in PCl in gram positive bacteria(17:00,i14:0,i15:1G,i15:0,a15:0,i16:0,i17:0,a17:0,i17:1?9c),gram negative bacteria(2OH-16:0,20H-16:1,16:l?7c,cy17:0,17:1?8c,18:1?5c,18:1?,18:lco9c,cy19:0),fungi(18:2?6,9c)and Actinomycetes(10Me17:0,10Me18:0).(3)Six months later,the decomposition rate of wheat and maize straw was between 42.75%and 57.92%.Ten months later,the decomposition rate was between 68.80%and 79.23%.There was no significant difference in the decomposition rate of straw in three soil textures.Total C content of straw scaled down during the straw decomposition,and Total N contents increased significantly,especially in the loam and clay.Six months later,total C content of the straw is significantly higher in clay soil than that in sandy.Ten months later,total C and total N content in the straw in different soil texture became similar gradually.(4)After six months decomposition,there were no significant difference in the content of microbial PLFA among the three soils.Ten months later,actinomycetes content showed significant difference,and was characterized by clay>loam>sandy soil.Straw decomposition for six months,fungi/bacteria ratio in clay was significantly higher than that in sandy soil,and no difference was observed after ten months.There was no significant difference in the ratio of monounsaturated fatty acid/saturated fatty acid among different texture soil after six months.Ten months later,the ratio in sand was higher than that in loam and clay soil,indicating that the air condition in sandy soil is the best.There was no significant difference in the ratio of cyclopropyl fatty acid/general saturated fatty acid among different texture soil after six months.Ten months later,the ratio in sand was lower than that in loam and clay,indicating a better microbial environment in clay soil.(5)The content of microbial and the ratio of fungi/bacteria changed with the change of distances from the straw residue,and the trend was straw residue inside>soil away from the mesh bag village>soil near the mesh bag.Microbial communities in soil microbial community and straw residue separated significantly along the PCl,and it is mainly caused by the gram positive bacteria(12:0,14:0,16:0,17:0,18:0,20:0,i13:0,i14:0,i15:0,a15:0,i15:0-3OH,i15:1 A,i15:1 G,i16:0,a16:0,i16:0-3OH,i16:1 G,i17:0,a17:0,i17:0-3OH),gram negative bacteria(3OH-12:0,2OH-16:0,3OH-16:0,16:lco5c,16:1?7c,16:1?9c,cy17:0,cy19:0,17:1?8c,18:1?7c,18:1?9c),fungi(18:2?6,9c,20:2co6,9c)and Actinomycetes(10Me 17:0,10Me 18:0). |
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