| Biochar is a solid material being rich in carbon and stable in nature,which produced from pyrolysis and carbonization of crop straw,animal excreta and other biomass,under the condition of complete or partial anoxic condition.The well-developed pore structure,rich surface functional groups and large specific surface area of biochar have great potential for soil improvement,mitigation of greenhouse effect,promotion of crop growth,and treatment of soil pollution.So,biochar is regarded as an effective soil conditioner by domestic and foreign scholars.Sulfur is the indispensable nutrients for crop growth and development.It directly participates biochemical reactions in the organism,regulates the metabolism of plants,and improves the quality of crops.Under the conditions of sulfur deficiency,the growth of plants will be hindered,even withered and dead.Therefore,sulfur is the most important nutrient after nitrogen,phosphorus and potassium.As a main type of soil in northwest China,light sierozem has the following main features: poor nutrition,loose structure,large porosity,poor agglomerating ability and low organic matter.Therefore,adding biochar to light sierozem could improve soil properties and structure and increase crop yields.Due to its physical and chemical properties,biochar added to the soil,will affect the migration and transformation of nutrient elements and soil microbial community structure.However,the effects of biochar on soil nutrient elements are mostly concentrated on nitrogen,phosphorus,and potassium.Rarely,the study for the transformation of sulfur,especially the sulfur reduction reaction of sulfur conversion,has been done in the presence of biochar.In the study,rape straw was used as biomass,and biochar was prepared at two pyrolysis temperature of 300 ℃ and 600 ℃(Labeled as BS300 and BS600).BS300 and BS600 were characterized by scanning electron microscopy,elemental analysis,FTIR and others,to analyze the structure and composition.Using flooding experiments,0%,1%,3% and 5% of BS300 and BS600 were respectively added to the light sierozem,to study the effects of two types of biochar on soil physicochemical properties,sulfur transformation,and soil microbial community structure.The aims are to provide a theoretical basis for migration and transformation of sulfur and changes of microbial community structure in light sierozem in the presence of biochar,under the anaerobic condition.The main conclusions are as following:(1)The yield and ash content of biochar were related to the pyrolysis temperature,and the yield of rape straw biochar decreased with increase of pyrolysis temperature,and the content of ash increased.The aromatization structure of BS600 is higher,the polarity and hydrophilic of BS300 are stronger.The results of scanning electron microscopy show that appropriate increase in pyrolysis temperature favors the formation of pore structure of biochar.FTIR test indicates that BS300 and BS600 contain rich surface functional groups.(2)Under the flooding condition,BS300 was added to light sierozem.It was found that the soil p H value,organic matter content and urease activity increased with the increase of BS300 added;the catalase activity in soil increased slightly,but the changes didn’t reach significant level.With the culture time increasing,total sulfur content in soil of control group and biochar added groups showed a decreasing trend,the descend range increased with the increase of adding biochar.Contents of total sulfur and inorganic sulfur in soil increased with the addition of BS300 increases.Total sulfur content reached a significant difference level compared with control group,with an increase of 0.4%,8.8%,and 21.2%.Through correlation analysis,it was found that total sulfur content in soil was positively correlated with p H value and organic matter content,no significant positive correlation with urease activity and catalase activity.Through Illumina Genome Analyzer IIx,soil samples with BS300 added at 0,1%,3% and 5%((Labeled BS300 a,BS300b,BS300 c and BS300d)were subjected to non-repetitive OTU clustering at 97% sequence similarity,yielding a total of 5,780 OTUs.The diversity analysis results showed that diversity of four samples was BS300 b > BS300 c > BS300 a > BS300 d.At the levels of the gate,the class and the genus,the dominant bacteria group of 4 samples had 10 gates,14 classes and 10 genera.The dominant genus of Desulfurispora was found in 4 samples at the genus level,and the content increased by 0.1%,0.3%,1.4% and 1.7% with the increase of BS300 addition.(3)Under the flooding condition,BS600 was added to light sierozem.With the amount of BS600 increasing,the p H value and organic matter content in soil were significantly improved.Soil urease activity was increased by 21.6% compared with the control group when the addition amount was 1%,and the difference was significant.The activity decreased by 0.7% and 9.3% when addition amount was 3% or 5%,and it reached a significant difference level.Activity of soil catalase slightly increased when amount of BS600 added,the change did not reach a significant level.With the increase of culture time,total sulfur content in soil of the control group and the biochar added groups showed a decreasing trend,the decrease range increased with the increase of added amount.The contents of total sulfur and inorganic sulfur in soil increased with the addition amount of BS600,which reached a significant difference compared with the control group.Through correlation analysis,it was found that there was a significant positive correlation between soil total sulfur content and p H value and organic matter content.However urease activity and catalase activity were no significant difference.Through Illumina Genome Analyzer IIx,soil samples with BS600 added at 0,1%,3% and 5%((Labeled BS600 a,BS600b,BS600 c and BS600d)were subjected to non-repetitive OTU clustering at 97% sequence similarity,yielding a total of 4799 OTU.The diversity analysis results showed that diversity of four samples was BS600 a > BS600 b > BS600 c > BS600 d,indicating that adding BS600 is not suitable for increasing soil microbial diversity under flooded conditions.At the levels of the gate,the class and the genus,the dominant bacteria group of 4 samples had 11 gates,13 classes and 10 genera.The dominant genus of Desulfurispora was found in 4 samples at the genus level,and the content increased by 0.2%,0.6%,1.7% and 2.2% with the increase of BS600 addition.(4)Comparing the effects of BS300 and BS600 on sulfur and microorganisms in soil,it was found that,under the same addition amount,BS600 increased significantly the soil p H value,total sulfur content,and desulfurization genus,while the richness and diversity of soil microbial communities of BS300 were higher. |
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