| Food security is the"cornerstone"of national economic and social development.Black soil region of northeast China,as the one of the four black soil regions in the world,is the important food production base and the"ballast stone"of national food security.Yet,Long-term high intensity utilization and soil erosion are triggering the frequent soil organic matter and nutrients loss of agricultural soil in the black soil area,which seriously threaten the security of national food and regional ecology.On the other hand,a large amount of agricultural waste is being produced,e.g.,straws,etc.,along with higher yield of grain.However,the unique geographical conditions and climate conditions restrict the composting of straw in the field to produce fertilizer and reuse,thus,the common way to deal with agricultural waste is"burning,discarding"and so on,resulting in serious resource waste and environmental pollution.Accordingly,how to realize the high-quality reuse of agricultural waste resources is a major problem in agricultural low-carbon development road.Hydrothermal humification technology was proposed by our group to prepare artificial humic substance as the raw of waste biomass（straw,fallen leaves,etc.）,aiming to effectively utilize solid waste resources and advance soil carbon content by applying artificial humic substance.Yet,the ket scientific problem corresponding to the effect and mechanism of artificial humic substance returning black soil on carbon turnover and stablish is unclassified.To solve the question,the research mainly studied systematically investigated the effects of different artificial carbon materials（liquid artificial humic substance/biochar,liquid artificial humic substance/solid artificial humic substance and liquid artificial humic acid/liquid artificial fulvic acid）on regulating soil biological carbon sequestration and the related mechanisms of soil carbon stabilization by different experimental conditions,e.g.,outdoor continuous cultivation experiment（including freezing,freezing-thawing,warming climates）and laboratory simulation experiments（including indoor simulated freezing-thawing and room-temperature experiments）,so as to seek the optimal application mode of artificial humus e.g.,suitable application doses and components,etc.,providing a theoretical basis and technological support for mitigating farmland soil carbon emission,improving soil carbon sequestration and mitigating greenhouse effect.The detailed results are as follows,The study firstly aimed to evaluate the potential of artificial humic substance for improving soil carbon sequestration with biochar as the control by observing the variation regularity of soil carbon content under the single or mixed application of biochar and liquid artificial humic substance through pot cultivation experiments under continuous natural climate conditions.The results demonstrate that three different applications of artificial carbon materials all triggered the loss of soil organic matter after 45-day cultivation（i.e.,freezing period）,and at least 0.31%,0.32%and0.94%of organic matter,respectively,was lost,while the soil organic matter of the soil treated by biochar was consistently decreasing with a specific loss of 0.14%after 180-day cultivation（i.e.,warming period）.In contrast,the soil organic matter of the soil treated by liquid artificial humic substance kept stable.The results of ultraviolet and fluorescence spectrum display that the remaining soil organic matter turned out to be more strongly humified and more stable,protecting the soil organic matter from fierce soil microorganism degradation through the warming season.Meanwhile,the results of high-throughput sequencing on the basis of 16S r RNA show that the application of liquid artificial humic substance effectively regulated soil bacterial community structure,e.g.,the further application of artificial humic substance on the basis of biochar can effectively inhibit the growth of Blastococcus sp.,a kind of bacterium with the function of degrading various carbon source to support its growth.Accordingly,liquid artificial humic substance functions to advancing the humification of soil dissolved organic matter and the stabilization of soil carbon.Based on the above results,we further observed the effect of liquid artificial humic substance doses on soil carbon sequestration and stability by indoor freezing-thawing simulation experiment.The results illustrate that 300 m L/kg liquid artificial humic substance effectively increased soil carbon content compared with that by 100 m L/kg liquid artificial humic substance under frequent freezing-thawing conditions,and the highest total organic carbon net increment was found as up to4000 mg/kg after 10 times freezing-thawing cycles.Ultraviolet spectroscopy,fluorescence spectrum and 13C nuclear magnetic resonance spectroscopy results reveal that liquid artificial humic substance devoted to the formation of more stable carbon under freezing-thawing events.Additionally,the results of amino sugar biomarkers demonstrate that liquid artificial humic substance significantly promoted the metabolic turnover of soil microorganisms,and significantly increased the content of fungal necromass carbon after soil freezing.Finally,the results of high-throughput sequencing corresponding to cbb L gene demonstrate that liquid artificial humic substance functioned to optimizing the community structure of carbon sequestration bacteria and improving the dominant position of part bacteria with strong carbon fixation ability to reduce soil carbon loss after thawing,e.g.,Mycolicibacterium gadium and Starkeya novella.Finally,to verify the mechanism of two major components of artificial humic substance（artificial humic acid and artificial fulvic acid）on soil carbon sequestration,the present investigation is to observe the change rule of carbon content in soil with different organic matter content on the role of liquid artificial humic acid and fulvic acid,obtained by acid extracting and alkaline dissolving.The results show that the effect of liquid artificial humic acid on soil carbon was better than that of artificial fulvic acid.Based on the results of nutrient elements content changes in soil,it can be found that both liquid artificial humic acid and artificial fulvic acid can significantly improve soil available phosphorus content and its migration distance,yet,the role of liquid artificial humic acid is more obvious.The results of surface planting technique show that the application of liquid artificial humic acid can promote the growth of bacteria,thus significantly increasing the biomass carbon content of bacteria,in comparison of that by liquid artificial fulvic acid.The results of fluorescence spectrum show that the addition of liquid artificial humic acid functions to promoting the conversion of soil dissolved organic carbon to aromatic carbon,and can enhance the degree of humification and carbon stability of soil dissolved organic matter,compared with that by liquid artificial fulvic acid.Finally,the results of high-throughput sequencing demonstrate that liquid artificial humic acid strongly supported the rapid growth of a photosynthetic Rubrivivax gelatinosus,so as to advance soil carbon sequestration.Overall,various application methods of artificial humic substance function to enhancing soil carbon sequestration and soil fertility in face of different climate conditions,which will provide theoretical basis and data for improving black soil fertility and reducing soil carbon emission. |
PDF Full Text Request