The Effect Of Straw Mulching On The Composition Of Soil Aggregates And Microbial Diversity

At the beginning of the 21 st century,a comprehensive scientific investigation on water loss and soil erosion and the ecological safety was carried out jointly by the Ministry of Water Resources,the Chinese Academy of Sciences and the Chinese Academy of Engineering,which answered the questions of soil erosion and ecological safety in Black Soil Region of Northeast China.Nearly half a century,owing to the fact that the farmland was overused without proper attention to the maintenance of its fertility and the unreasonable farming,as well as a series of characteristics such as concentrated rainfall,overspread hill topographic features,the clay of the parent material,loose topsoil and so on in the northeast,which resulted in the deterioration of soil structure,the decrease of the content of the soil organic matter,the decrease of soil microbial diversity and activity.The degree of soil erosion is increasing,and the surface erosion and furrow erosion develop rapidly,which are the main factors restricting the construction of the ecological environment and the agricultural production in the black soil region.Therefore,the prevention and control of water loss and soil erosion in sloping farmland in Black Soil Region of Northeast China has become an important research topic at present.In this experiment,the typical sloping farmland in Black Soil Region of Northeast China as the research object,based on the farming area of the small watershed of the Qing River in Yitong River,Jilin province.Through the determination of soil aggregate,N and P nutrient analysis and determination of high-throughput sequencing microbial diversity of the combination of research methods,the effects of slope and straw mulching on soil aggregates,N and P nutrient losses and soil microbial diversity under natural conditions were studied and evaluated.The effect of straw mulching on water loss and soil erosion in sloping farmlands is revealed in order to provide the theoretical guidance for the comprehensive prevention and control of soil erosion and soil degradation and the "turning waste into treasure" of corn stalks in Black Soil Region of Northeast China.The main conclusions are as follows:(1)Deals with straw mulching compared with not covered,the mechanical stability of > 0.25 mm aggregate and aggregate content of water stability increased,and the same change trend,are all 9 °> 6 °> 3 °.By the contrast of scanning electron microscopy,the treatment of furrow straw mulching was beneficial to the formation of large aggregates of soil.(2)In one cycle,the MWD and GMD values of the soil aggregates were increased by the furrow mulching.Moreover,MWD and GMD of soil water stability aggregates increased significantly with the increase of slope.At the same time straw mulching reduces the fractal dimension of soil aggregates.(3)Compared with the same slope,the soil moisture content of furrow straw mulching was higher than that of uncovering,which was 1.06 times,1.09 times and 1.37 times.The annual runoff and annual runoff coefficient of furrow straw mulch are significantly less than that of uncovering.It is shown that furrow straw mulching can effectively reduce the stock flow of slope and reduce runoff velocity,which is beneficial to water infiltration.(4)Through the determination and analysis of the contents of N and P elements in the farmland and the lost soil in the runoff plots,it can be concluded that the whole straw mulching reduces the N and P nutrient transfer significantly,thus improving the utilization rate of N and P nutrients in farmland soil.(5)High throughput sequencing technology was used to analyze soil bacterial diversity under furrow straw mulching.The results showed that there were 439 OTU in the six groups of soil samples,and the total number of OTU was 419.The richness and diversity of 9JG were the highest.In various soil samples were 15 groups of bacteria,the proportion is in turn: Proteobacteria>Acidobacteria>Gemmatimonadetes>Bacteroidetes>Actinomycete>Nitrospira>C hloroflexi> Latescibacteria > Saccharibacteria Verrucomicrobia > Phylum Firmicutes> Armatimonadetes > Chlorobi> Elusimicrobia > Euryarchaeota.In which Proteobacteria and Acidobacteria are a dominant group of bacteria.(6)In the analysis of the diversity of soil fungi,there were 241 OTU Numbers,109 of which were total OTU Numbers.The number of species covered with straw was larger than that without mulching.Among the 6 soil samples,the fungi included in the portal level included Ascomycota,Basidiomycota,Glomeromycota,Zygomycota and Chytridiomycota.The proportion of the 6 fungi groups was: Ascomycota > Basidiomycota > Glomeromycota > Zygomycota > Chytridiomycota.Ascomycota and Basidiomycota were the dominant bacteria in each sample.