Effects Of Organic Materials On Soil Properties And Alfalfa Growth

Biochar,as a new soil improvement material,has an excellent regulation effect on soil physical,chemical and biological properties,and also plays an important role in crop growth and carbon fixation.However,direct comparative studies on the effects of other traditional plant residues and related transfers（straw,humic acid,compost and livestock manure）on soil,environment and plants are still lacking.Therefore,the effects of biochar and traditional plant residues and their conversion（straw,humic acid,compost and cow manure）on soil,plants and carbon emissions were investigated in this study,in order to provide a theoretical basis for rational utilization of plant residues and their conversion products.The main research results are as follows:（1）Several organic materials can improve the physical and chemical properties of soil,but there are differences among different materials.The contents of total carbon and available potassium in soil treated with biochar were significantly higher than those treated with other materials,while the content of available phosphorus was significantly lower than that treated with compost and humic acid,and the content of total nitrogen in soil treated with 5.0%biochar was significantly higher than that treated with straw,humic acid and compost.Soil CO₂emission from biochar treatment was significantly lower than that from other materials treatment.In addition,the soil bulk density of biochar treatment was significantly lower than that of humic acid,compost and cow manure treatment,but had no significant difference with straw treatment.Field water capacity was significantly higher than that of other materials.（2）Different materials also had significant effects on soil biological properties.Compared with other materials,biochar significantly reduced the diversity of soil bacterial community,significantly increased the relative abundance of Actinomyces,Sphingosinomonas and Pseudomonas,but decreased the relative abundance of RB41.Compared with straw treatment,the relative abundance of Chloroflexi,Acidobacteria and Bacillus was significantly decreased,but the relative abundance of Streptomyces was increased.The relative abundance of Rhizobium was significantly higher than that of compost and cow manure.Compared with other materials,biochar treatment significantly decreased the richness of soil fungi,compared with straw treatment significantly increased the relative abundance of Ascomycota,Stachybotrys and Penicillium,and compared with straw and cow manure treatment significantly decreased the relative abundance of Mortierella.In addition,compared with straw,humic acid and compost treatments,biochar significantly increased the relative abundance of soil pathophysiological fungi,and significantly decreased the relative abundance of saprophytic fungi and symbiotic-saprophytic fungi.In addition,the urease activities of soil treated with biochar were significantly lower than those treated with straw,compost and cow manure,while the sucrase and phosphatase activities of soil treated with biochar were significantly higher than those treated with humic acid.（3）Several kinds of materials all promoted the growth and development of alfalfa root system,increased the plant height,stem diameter and branch number of alfalfa,and then increased the yield.Biochar had the best effect on alfalfa yield.Compared with straw,humic acid,compost and cow manure,the yield of alfalfa treated with 3.0%biochar was significantly increased by 11.47%,28.26%,17.39%and 21.31%.In conclusion,these materials improved soil physicochemical properties,regulated soil microbial community structure and enzyme activities,and promoted the growth of alfalfa.However,different materials have different effects due to different composition and properties.