A Simulation Study On The Relationship Between Black Soil Acidification And Soil Organic Carbon Change

Numerous studies have shown that the heavy application of chemical fertilizers,especially nitrogen fertilizers,is the main factor of soil acidification in agricultural fields,and Jilin province is the main corn producing area in China,which has contributed greatly to ensuring food security in China.However,the excessive use of chemical fertilizers,especially nitrogen fertilizers,along with high maize yields,has made the acidification of black soils in the maize belt of Jilin increasingly prominent.The acidification of black soils leads to a decrease in salt base saturation and organic matter content,a decrease in cluster stability,soil structure deterioration,and consequently soil fertility degradation,which poses a serious threat to food production and the stability of farmland ecosystems.Therefore,a fertilizer drenching test was used to simulate the acidity changes of black soils under different fertilizer application years to reveal the relationship of organic carbon changes during black soil acidification,to provide theoretical basis and data support for mitigating and preventing black soil acidification and protecting black land.1.The relationship between fertilization and black soil acidification and the amount of organic carbon was quantified.The results of the 25-year simulated fertilization drenching test showed that the simulated fertilization drenching black soil p H decreased by a total of 0.85 units and organic carbon content decreased by 22.76%.The study showed that nitrogen entering the soil system accelerates soil acidification through nitrification to produce H⁺.The simulated25-year fertilization treatment group showed a significant decrease in p H,and in soil organic carbon content,the simulated 25-year fertilization treatment group also showed a significant decrease（P<0.05）,and the correlation analysis indicated that soil acidity was positively correlated with organic carbon content.2.The effect of continuous acidification of the simulated fertilized drench black soil on the stability of the agglomerates was clarified.The dry sieve method and wet sieve method tests showed that the mechanical stability and water stability of the simulated fertilized drench black soil decreased with the decrease of soil p H.The results of water stability of agglomerates showed that the water stability of 5-3 mm agglomerates decreased with increasing soil acidity,and the kinetic characteristics of the water stability of agglomerates showed that the water stability of agglomerates of simulated fertilized drenched black soil decreased with increasing soil acidity.From the results,the GMD of the simulated fertilized drenched black soils decreased,indicating that the soil agglomeration was lower.Comparing the organic carbon content of the water-stable agglomerates at each grain level of the black soils with different treatments,it can be seen that the organic carbon content of the water-stable agglomerates at each grain level showed an overall trend of significant decrease with increasing acidity,indicating that the organic carbon content was gradually decreasing with the continuous acidification of the black soils.3.Different treatments affected the humus of each binding state to different degrees,and the deepening of soil acidification significantly increased the humus content of loose-knotted state,and the loose-to-tight ratio of soil humus also significantly increased,and the HA organic carbon content in loose-knotted humus significantly increased,and FA showed a trend of first decreasing and then increasing,indicating that soil acidification would promote the transformation of steady-knotted humus to loose-knotted humus,which has a certain influence on Soil acidification has a certain influence on soil stability.The H/F of loose-knotted humus increased significantly with acidification,and the H/F of steady-knotted humus decreased continuously,and the H/F of steady-knotted humus was less than 1.00,indicating that the stability of soil organic carbon decreased with acidification.the PQ value decreased from48.28%to 23.57%with acidification,and the decrease of PQ value indicated that the acidification process inhibited the humification process.TheΔlg K values of loose-knotted humic huminic acid and fulvic acid were higher and lower at different acidity levels,and theΔlg K of stable-knotted humic huminic acid did not change significantly at different acidity levels,while theΔlg K of stable-knotted fulvic acid was significantly lower in acidified soil than in CK treatment.With the deepening of acidification,the E4/E6 of loose-knotted humus increased,and the E4/E6 of steady-knotted humus did not change significantly,indicating that acidification reduced the degree of condensation of loose-knotted humus in the experimental acidity range and had no significant effect on the humification process of steady-knotted humus.4.With the deepening of simulated acidification,the CEC_8.2content showed a significant decrease,the CEC_Pcontent showed a significant increase,the CEC_vcontent showed a significant decrease,and the AEC content showed a significant increase.The decrease of organic matter leads to the decrease of CEC_8.2in the soil clay grain level complex,the change of CEC_Pis not caused by the change of organic matter content,but the decrease of soil organic matter inhibits the replacement of clay grain minerals and reduces its quantity,there is a correlation between CEC_vand soil acidity,when p H decreases,the CEC_vcontent of the soil clay grain level complex decreases,AEC and organic matter There was a significant negative correlation because the presence of organic matter was not conducive to the adsorption of phosphate by the soil mucilage-level complex.5.Among the different acidification treatments,the simulated 25-year fertilization treatment group possessed a lower number of OTUs.,the simulated 25-year fertilization treatment as a significant negative correlation because the presence of organic matter was not conducive to the adsorption of phosphate by the soil mucilage-leat acidification treatments produced substantial changes in the microbial community.At the phylum level,the relative abundance of the soil phylum Aspergillus was elevated and then decreased,while the phylum Acidobacter and Bacillus significantly decreased（P<0.05）and the phylum Synechococcus and Bacteroides patellae elevated.Redundancy analysis（RDA）showed that the phylum Bacillus patellae,Bacillus phylum and Bacillus phylum were positively correlated with AK,AP and AN,and negatively correlated with p H and SOC.Acidobacteria,Phyllobacterium spp.,Mucor phylum,and Green Bacteria phylum were positively correlated with p H and SOC,and negatively correlated with AK,AN,and AP.In conclusion,the acidification of black soils reduced the organic carbon content of soils,and the organic carbon of agglomerates was enriched to>2 mm particle size with the deepening of acidification,and the acidification promoted the conversion of stable to loose-knotted humus and reduced the condensation of loose-knotted humus.The stability of soil organic carbon decreased with the deepening of acidification.CEC_8.2was the main electrochemical factor affecting the amount of organic carbon during acidification,and the amount of Acidobacteria phylum,Mucor phylum and Green Curvilinear phylum were the main factors affecting the amount of organic carbon during the acidity change.