Study On The Effect Of Aluminum Sulfate Improver On Carbon Sequestration Of Soda-alkali Soil

Studying the carbon sequestration performance and the potential of soda saline-alkaline soil can reveal the mechanism of carbon sequestration of soda saline-alkaline soil with aluminum sulfate,enrich the theory of fertilization improvement of soda saline-alkaline soil,and provide theoretical basis for formulating suitable fertilization measures of saline-alkaline soil.In this study,the soda saline-alkaline soil in Lesheng Township,Anguang Town,Da'an City,Jilin Province,was used as experimental soil,and aluminum sulfate was used as the modifier,corn straw was added in different proportions,through the indoor simulated culture experiment and adsorption experiment,the changes of main physical and chemical parameters of soda saline-alkaline soil under the effect of additives were revealed,the adsorption characteristics of humic acid in soil were studied,and the carbon sequestration properties of humus carbon,corn straw carbon and their conversion products were revealed,which provided theoretical basis for the improvement of soda saline-alkaline soil ecological environment and sustainable utilization of farmland.The results are as follows:First,Adding aluminium sulfate and corn straw can reduce the pH of soda saline-alkaline soil.No matter how much corn straw is added,when the amount of aluminum sulfate is 0.8%,the acidification of soda saline alkaline soil is no longer obvious;while adding the same proportion of aluminum sulfate,adding corn straw will also make soda saline-alkaline soil the pH drop,by an average decrease of 0.4-0.5 units.Therefore,adding aluminium sulfate and corn straw at the same time to reduce the pH of soda saline-alkaline soil is the leading role by aluminium sulfate.Adding aluminium sulfate and corn straw changed the composition of soluble salt in soda saline-alkaline soil,the contents of Na⁺,K⁺,Ca ²⁺and Mg ²⁺increased,while the contents of CO₃^2-and HCO₃^-decreased gradually.Adding aluminium sulfate and corn straw can increase cation exchange capacity?CEC?in soda saline-alkaline soil,and cation can replace exchangeable sodium in soil colloid,thus reducing the alkalization degree of soda saline-slkaline soil.Second,the total organic carbon,heavy fraction organic carbon matter and compound quantity were added with the aluminium sulfate and corn straw in soda saline-alkaline soil,but the compound degree showed a gradually decreasing tread.The heavy fraction organic matter was higher in the treatment of corn straw and aluminium sulfate than in the treatment of aluminium sulfate or corn straw alone.The change trend of heavy fraction organic matter in soda saline-alkaline soil was not obvious when aluminium sulfate was applied alone.When corn straw was added at 15%,the content of heavy fraction organic carbon in soda saline-alkaline soil increased,which indicated that soda saline-alkaline soil still had great carbon sequestration potential.Third,the content of micro-aggregates in soda saline-alkaline soil changed obviously with the addition of aluminium sulfate and corn straw.With the increase of the aluminium sulfate and corn straw,the content of 2-0.25 mm micro-aggregates increased significantly,while the content of 0.25-0.05,0.05-0.01,0.01-0.005,0.005-0.001 and<0.001 mm micro-aggregates decreased gradually.The results showed that the addition of aluminium sulfate and corn straw in soda saline-alkaline soil promoted the agglomeration of small-sized micro-aggregates to large-sized micro-aggregates,which resulted in the increase of the content of large-sized micro-aggregates.Fourth,under the condition of adding aluminium sulfate and corn straw,organic carbon in micro-aggregates of soda saline-alkali Soilne increased significantly.With the addition of aluminium sulfate and corn straw,the change trend of organic carbon content in 2-0.25 mm micro-aggregates was not obvious,but the content of organic carbon in<0.25 mm size increased with the increase of aluminium sulfate and corn straw.The contribution rate of micro-aggregates with 2-0.25 mm size was the largest.Adding aluminium sulfate and corn straw can not only increase the content of large-sized micro-aggregates,but also increase the contribution rate of organic carbon of large-sized micro-aggregates in soda saline-alkaline soil,which was beneficial to improve the fixation performance of organic carbon.Fifth,under the condition of adding different proportion of corn straw and aluminium sulfate,the adsorption of humic acid on saline-alkaline soil reached equilibrium at 120 minutes,and the fitting effect of pseudo-second-order kinetic equation was the best,and R² value was the highest?0.936?.Langmuir equation and Freundlich equation can be used to fit the isothermal adsorption of humic acid on saline-alkaline soil.Under the same proportion of corn straw,the maximum adsorption capacity obtained by Langmuir equation respectively fitting was 69.335,42.830,40.498 and 42.593 mg/g.The maximum adsorption capacity was 21.358 mg/g,32.647mg/g,69.335 mg/g,49.232 mg/g,62.375 mg/g and 42.830 mg/g with the same proportion of aluminum sulfate.