Improvement Effects And Mechanisms Of Biochar And Compost On Sandy Soil In The Songnen Plains

The junction of Eastern Khorchin and Western Songnen plains is located at the transitional zone of semi-humid-semi-arid climate,which was suffered serious vegetation destruction and land desertification under the disturbance of natural and artificial effects.The land desertification severely restricted the local land productivity and restrained the sustainable development of social economy and ecological environment.The songnen plains in Western Jilin Province region was selected as the study area in this paper,and the field trials were designed.Five treatments（no amendment,biochar,compost single or joint application）were set,and the experiment last for 3 years.The changes of soil physicochemical properties after single and joint addition of bochar and compost were analyzed to discuss the persistent effect of the amendments.The another 3 treatment(no amendment,lower content of biochar(10t ha^-1)and higher content of biochar(20t ha^-1)joint with compost(40t ha^-1)seperately)were set,and 4 kinds of crop species were selected for split plot design.Biodiversity level and composition of the soil bacterial,fungal and AM fungal community after the addition of soil amendments were analyzed by the high-throughput sequencing analysis,and the internal mechanism of these two kind of soil amendmens were analyzed.The results are as follows.（1）Biochar and compost improved the soil physicochemical properties.The soil water holding capacity,electric conductivity,content of total organic carbon,total nitrogen,available nitrogen,available phosphorus and available potassium,soil carbon nitrogen ratio and water solubale aggregation were increased after the additon of soil amendments,and the bulk density were declined,especially in the treatment of biochar joint with compost which is significant different with control.The content of soil organic carbon and carbon nitrogen ratio were increased significantly after the single addition of biochar or jointed with compost.The application of the soil amendments significantly increased the soil cation exchange capacity,and the effect of the latter two years was stronger than that of the first year.Moreover,the joint effection of biochar and compost were showed on the soil bulk density,water holding capacity,aggregate stability,electrical conductivity,cation exchange capacity,content of total organic carbon,total nitrogen and total phosphorus.（2）The application of biochar and organic fertilizer significantly increased the diversity of soil bacteria and improved soil structure.The Chao1 index,Shannon index and Richness index were significant improved after the addition of biochar and compost,and the bacterial community’s biodiversity index was correlated signifi-cantly with soil physicochemical properities,which showed that the biodiversty was increased after the improvement of soil properties by amendments addition,while the species of crop had no significant effect on the biodiversity of soil bacterial community.The relative abundance of different bacterial taxa were got by OTU cluster,it showed that the relative abundance of Citrobacter,Acinetobacter and Pseudomonas and Massilia in Proteobacteria decreased significantly after the joint additon of biochar and compost.Most of these bacteria are pathogen,suggesting that the addition of the amendments can inhibit some pathogenic bacteria flora,and promote other groups of bacteria proliferation,thus reduce the incidence of underlying diseases,which is good for health and stability of the soil ecosystem.The abundance of Sphingomonas,Nitrobacter and Rhizobium in Protecbactria,Aridibacter in Acidobacteria and Gemmatimonas in Gemmatimonadetes were increased significantly after the addition of amendments,and these bacteria are conductive to nirogen fixation or can improve stress insistence.It was showed that the soil amendments played an more important role in the effect on soil microbial groups than crop types by species richness heatmaps and PCA.（3）Biochar and compost affected the composition and structure of the soil fungi and AM fungi.The biodiversity of soil fungal was not significant changed after the application of biochar and compost,but the abundance of some fungi in the sandy soil which can cause soil-born disease decreased after improved by the amendments,while some fungi which have the effect of prevention was inhibited,too.In addition,Podospora fungi in the rhizosphere soil was extremely significant increased after amendmet,which is shown that biochar and compost can increase the inhibitory effect of soil-borne diseases.After the application of biochar and organic fertilizer,the fungal infection rate of the crop roots was reduced,but the biodiversity of AM fungal community was not changed significantly.The relative abundance of Archaeosporales,Geosiphonacea and Ambispora were increased significantly after the addition of amendments,and the relative abundance of Glomus were significant higher in rhizosphere of two kinds of Vigna radiata than two kinds of Vigna angularis.PLS-DA showed that the crop types affect the soil AM fungi significantly.（4）The biomass and yield index was significant improved by the application of biochar and compost,and even in the treatment of small amount of biochar mixed with compost.The application of high concentration of biochar mixed with compost significantly increased the biomass of organs,number of pods per plant,yield,100-kernel weight,and low concentration of biochar mixed with compost can affect on the yield and reproductive allocation significantly.Correlation analysis showed that content of total organic carbon,total nitrogen,total phosphorus were significantly positive correlated with the yield of crops.The yield of 2 kinds of Mungbean was significantly negative correlated with pH and positive correlated with EC.It can be seen that a certain proportion of biochar and compost can be applied to the sandy soil as organic amendments to improve the soil’s nutrient content,regulate pH and EC,and increase crop yields.These findings not only provided the insight into the improvement effect of biochar and compost on the physicochemical properties of sandy soil and soil microflora,but also facilitated the study of restoration ecology in degraded soil.The results of this stuty may provide theoretical and experimental basis for the research of soil bacterial and fungal communities structure and the sustainable utilization of sandy soil.