Study On Interaction Mechanism And Application Of Soil Acidification Improved By Potassium And Magnesium In Tea Garden

Tea garden soil is still in the trend of acidification,both potassium and magnesium fertilization alone can increase soil p H in tea gardens,and studies have found interaction between potassium and magnesium in plants.Soil as a source of plant nutrients,the potassium-magnesium interaction effect in soil and its improvement effect and improvement path on acidified tea garden soil have not been clarified.Therefore,this study collected acidified soil from tea gardens for indoor culture experiments,set potassium and magnesium fertilizers with different concentration levels,analyzed the effects on p H,Exchange Cation content and nitrogen morphological transformation at different incubation times,and constructed structural equation models,revealed the interaction mechanism of potassium and magnesium to improve soil acidification.At the same time,the potassium and magnesium fertilizer concentrations with the best improvement effect were used for further field experiments to analyze the effects and correlations on soil p H,nutrients,bacterial communities and tea plant yield quality,and to explore the application effect of potassium and magnesium fertilizers in tea gardens,so as to provide a theoretical basis for the rational application of potassium and magnesium fertilizers.The main findings are as follows:1.The interaction effect of potassium and magnesium existed in soil under different concentrations of potassium and magnesium fertilizers.Antagonistic effect:the antagonism of potassium to low magnesium(0,100mg·kg^-1)increased with the increase of potassium fertilizer concentration,while the antagonism of high potassium(200 mg·kg^-1)to magnesium decreased with the increase of magnesium fertilizer concentration,the antagonism of magnesium to low potassium(50 mg·kg^-1)increased with the increase of magnesium concentration.Synergistic effects:medium potassium(100 mg·kg^-1)had synergistic effect on medium magnesium(200 mg·kg^-1),and medium potassium(100 mg·kg^-1)had synergistic effect on high magnesium(400 mg·kg^-1).The antagonism between potassium and magnesium was stronger than the synergistic effect,and the antagonism of potassium to magnesium was stronger.2.The interaction of potassium and magnesium improved the acidified tea garden soil.Each potassium and magnesium treatment of soil p H was average increased by 0.12～0.60 units,and the treatment of low potassium and high magnesium(50 mg·kg^-1 of potassium fertilizer+400mg·kg^-1 of magnesium fertilizer)had the best effect.Each potassium and magnesium treatment of Exchangeable K⁺,Exchangeable Mg²⁺and Exchangeable Na⁺content average increased by 34.57%～112.77%,87.54%～271.04%and 5.07%～34.06%,respectively,Exchangeable Al³⁺and Exchangeable H⁺content average decreased by 14.31%～34.95%and13.93%～30.01%,respectively.Compared with CK,the decrease range of NH₄⁺-N content and the increase range of NO₃^--N content in each potassium and magnesium treatment were smaller,delayed the tea garden soil nitrification process.3.The main pathway of potassium and magnesium interaction to improve acidified tea garden soil.The main improvement paths from strong to weak were:the direct effect of Exchangeable Mg²⁺on p H,the indirect effect of Exchangeable Mg²⁺on p H by negatively affecting Exchangeable Al³⁺,the direct effect of Exchangeable K⁺on p H,and the indirect effect of Exchangeable K⁺on p H by positively affecting Exchangeable Na⁺,the path coefficients were 0.82,0.16,0.15,0.05.4.The application effect of potassium and magnesium fertilizer in tea gardens is good under different application amounts.When the low amount was applied（potassium fertilizer 8 kg/mu+magnesium fertilizer 64kg/mu）,the Total Potassium and Available Potassium content in autumn,One Bud Weight of spring and autumn tea and Total Amino Acid of spring tea were the most significant,with an average increase of 34.67%,85.48%,15.24%and 13.28%,respectively,and significantly changed the bacterial community structure,the abundance of Proteobacteria and Bacteroidota increased by 12.30%and 126.56%,and the abundance of Firmicutes and Actinomycetes decreased by 86.35%and 14.02%.When the high amount was applied（potassium fertilizer 16 kg/mu+magnesium fertilizer 128kg/mu）,the soil p H in spring and autumn,Available Potassium and Organic Matter content in spring,Available Phosphorus content in autumn,Germination Density of autumn tea,Water Extract,Total Amino Acid and caffeine content of autumn tea were the most significant,with an average increase of 0.63 units,26.96%,99.21%,100.32%,14.42%,7.79%,12.73%and 30.37%,respectively.RDA and Pearson analysis showed that potassium and magnesium combined application positively regulated p H,Available Potassium and Total Nitrogen content,Proteobacteria and Bacteroidetes abundance,and negatively regulated Firmicutes and Actinobacteriota abundance,thus,the yield and quality of tea can be increased,and the effect on tea plant is stronger when the amount of application is low.In conclusion,the antagonistic effect of potassium and magnesium on acidified tea garden soil was stronger than the synergistic effect,especially the antagonism of potassium to magnesium（potassium to low magnesium,high potassium to magnesium）.Under the interaction of potassium and magnesium,the soil acidification of tea garden was improved,the main improvement path is the direct effect of Exchangeable Mg²⁺and Exchangeable K⁺on p H,and the indirect effect of Exchangeable Mg²⁺and Exchangeable K⁺on p H by negatively affecting Exchangeable Al³⁺and positively affecting Exchangeable Na⁺,respectively,the treatment of low potassium and high magnesium(50 mg·kg^-1 of potassium fertilizer+400mg·kg^-1 of magnesium fertilizer)had the best improvement effect.After the application of low potassium and high magnesium treatment in tea gardens,it can increase the yield and quality of tea plants by promoting the soil p H,Total Nitrogen and Available Potassium content of tea garden,and the abundance of Proteobacteria and Bacteroidota.Therefore,when applying potassium and magnesium fertilizer to manage acidified tea gardens,it is necessary to appropriately reduce potassium and magnesium supplementation to balance soil potassium and magnesium nutrition.