| The existence of nutrient elements and their transformation affect the growth and metabolism of plants directly.How to use the nutrients of the soil scientificly and effectively,and to convert it into a form that can be directly used by crops,it is beneficial to increasing crop yields and improving the environment of agricultural ecological.Sulfur is an indispensable nutrient for crop growth and development.It is ranked after nitrogen,phosphorus and potassium accoreding to the demand of the plants.Although the content of sulfur in the soil is few,it is an important part of the soil material cycle and participates in many chemical equilibrium reactions.The oxidation and reduction of sulfur in soil is of great significance to the soil ecological environment.However,due to natural leaching and unbalanced long-term fertilization,coupled with the policies that limit sulfur emission in order to prevent atmospheric pollution,the problem of soil sulfur deficiency is increasingly serious.The light sierozem is one of the main soil types in the northwest of China.The soil is poor and its fertility is low,its porosity is low and the water permeability is poor,and the nutrient elements are leaching.In Lanzhou of Gansu province,urea,phosphate fertilizer and carbon ammonia are the main fertilizers,resulting in potential sulfur deficiency in the soil.Therefore,how to use the sulfur from soil fully to oxidize reduced sulfur into sulphate compounds that plants can use directly is very important for promoting plant growth and improving the status of soil sulfur deficiency.Biochar is a porous,carbon-rich,highly aromatic material that obtained by biomass pyrolysis under limited oxygen conditions.Biochar has large specific surface area and well-developed pore structure.It has high application value in areas such as environmental remediation and soil improvement,and it has been payed widespread attention in the academic community.At present,there are many studies about that the effect of biochar on nitrogen and phosphorus in soil.However,the research about the effect of biochar on sulfur is rare.Therefore,in this paper,biochar was obtained from rape straw pyrolyzing at 300°C and 600°C(marked as BS300 and BS600 respectively),and mixed with light sierozem in proportions of 0%,1%,3% and 5% respectively(maked as CK,BS3001,BS3003,BS3005 and CK,BS6001,BS6003,BS6005).The mixture is incubated under aerobic conditions at 25±1°C,and the cultivate period is setted as 12 weeks.Analysing the effects of different amounts of biochar on the variety trend that soil physicochemical properties,enzyme activity,and the content of various forms sulfur changed with the incubation time,and researching the effect of different biochar application on soil physicochemical properties and sulfur transformation when the experiment is finished.High-throughput sequencing technology was used to analyze the changes of the number,abundance,community structure,and diversity of soil microorganisms after application of biochar.It will provide a theoretical reference for the application of biochar in improving soil environment.The main results are:(1)When biochar is applied to the soil,the soil pH,electrical conductivity,organic matter content and urease activity can be increased,and it has a little influence on catalase.The influence of biochar on the physicochemical properties of soil is related to the cultivation time and the application amount of biochar.Soil pH and electrical conductivity increased at first,then decreased and increased after that with time,soil organic matter content is increased at first and then decreased,and soil urease activity firstly increased and then decreased with time.After 12 weeks of incubation,the increase or decrease extent of these indexes is different along with the biochars? application,.When the amount of BS300 application was 0%,1%,3% and 5%,the pH is increased by 3.2%,4.7%,3.1% and 0.7%,respectively,and the soil conductivity is increased by 47.5%,18.3%,9.9% and-14.3%,respectively.After applying 0%,1%,3% and 5% BS600,the pH decreased by-3.2%,1.9%,4.9% and 3.3%,respectively,the conductivity is increased by 47.5%,51.7%,25.4% and 27.2% compared to the initial value.Soil pH value,electrical conductivity,and organic matter content may increase significantly with the increase of biochar application amount.At the end of the incubation period,soil pH values were increased by 5.4%,7.8%,9.7% and 6.3%,12.6%,18.1% when the application rates of BS300 and BS600 were 1%,3%,and 5%,respectively.Soil electrical conductivity increased by 23.4%,71.4%,78.9% and 41.1%,90.9%,178.6% compared with the control group,respectively,Organic matter content was more than twice that of the control group.Soil urease activity is decreased with the increase of the amount of BS300 applied,and there is a significant difference.The catalase activity has no significant change with the amount of biochar application.(2)The content of various forms of sulfur in soil is varied with the incubation time,and the range of variation is different with the amount of biochar application.The soil total sulfur,content is decreased firstly,then increased,after that decreased with the incubation time,so do soluble sulfur,adsorbed sulfur,and hydrochloric acid soluble sulfur.The organic sulfur content is increased at first and then decreased.After 12 weeks of incubation,the increase or decrease extent of each form sulfur is different along with the biochars application.When the application amount of BS300 is 0%,1%,3% and 5%,the total sulfur content is decreased by 25.8%,30.4%,25.4% and 26.6%,respectively.The water-soluble sulfur is decreased by 58.9% and 57.2%,30.2% and 66.9%,respectively.The adsorbed sulfur is decreased by 54.6%,62.2%,69.2% and 72.2%,respectively,and the hydrochloric acid soluble sulfur content is decreased by 51.3%,50.2%,50.0% and 57.8%,respectively.When the application amount of BS600 is 0%,1%,3% and 5%,the reduction extent of water-soluble sulfur is 58.9%,52.2%,53.7% and 49.3%,respectively,and the reduction of adsorbed sulfur is 54.6%,66.0%,64.5% and 66.9%,respectively.the hydrochloric acid soluble sulfur is increased-51.3%,3.4%,14.2% and 28.5%,respectively.In addition,the content of every forms of sulfur varies significantly with the amount of biochar application.The content of water-soluble sulfur and hydrochloric acid soluble sulfur increases firstly and then decreases with the increase of the amount of BS300,and the difference is significant.They increase significantly with the increase of the amount of BS600.The content of adsorbed sulfur does not change significantly with the amount of BS300.It is increased with the addition of BS600 application,but no significant difference.(3)After 12 weeks of incubation,the bichar-applied soil was compared with the soil without biochar,the number of OTU of soil microbial community is decreased,its evenness is also decreased,and the abundance of OTU is increased.With the increase of biochar application,the difference of abundance among OTU is obvious.When biochar is applied,the diversity of microorganisms in the soil is increased,and the change is related to the amount of biochar application.The sequence of the Chao1 exponents among every sample group is: BS3001(29)BS3005(29)CK(29)BS3003,CK(29)BS6001(29)BS6005(29)BS6003,and the ACE index is the same as Chao1;the Shannon index sequence is: BS3001(29)BS3005(29)CK(29)BS3003,BS6003(29)CK(29)BS6001(29)BS6005.Bacterial community structure of every soil samples had high diversity at each level when they are in different biochar treatment.There is 36 phylum,100 class,130 order,200 family,250 genus,and 110 species.Including Proteobacteria,Gemmatimonadetes,Planctomycetes,Cyanobacteria,Acidobacteria,Actinobacte ria,Chloroflexi,Euryarchaeota,Firmicutes,Nitrospirae,Bacteroidetes and so on.The proportion of each microbial group in the samples with different biochar application amounts is various.At the phylum level,proteobacteria is the most,in the CK,BS3001,BS3003,and BS3005 samples accounted for the average They are 32.1%,27.8%,31.0%,and 23.4%,and in the CK,BS6001,BS6003,and BS6005 samples are 32.0%,31.8%,24.8%,and 30.3%,respectively.The microbial community structure of the sample groups corresponding to the application of biochar is obviously different.The microorganisms that contribute significantly to the differences among the BS300 group include Proteobacteria,Bacteroidetes,Bradyrhizobium.The major contributors to the differences between the BS600 group are Actinobacteria,Bacteroidetes,Proteobacteria.The community structure of microorganisms is influenced by biological factors and abiotic factors(such as environmental factors).There is a correlation between the physicochemical properties of soil,the contents of various forms of sulfur and soil samples.In summary,the application of biochar can change the soil physicochemical properties and enzyme activity of the light sierozem soil,affect the transformation of sulfur in the soil and microbial community structure and its diversity.Biochar has a significent improvement effect on the soil environment of light sierozem. |
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