Effects Of Modified Biochar On Soil Fertility And Tea Tree Growth In Acidified Tea Garden

Soil acidification refers to the increase in H⁺and the decrease in base ions in the soil.It results from the release of Al³⁺from the lattices of soil clay minerals and the exchange of H⁺and Al³⁺with exchangeable base ions,resulting in the leaching of base salts and the increase in exchangeable H⁺and Al³⁺,hence,soil acidification.In recent years,the acidification of tea garden soils in Fujian province has intensified,resulting in the decline in tea yield and quality.Therefore,taking scientific and effective measures to ameliorate the acidification of tea garden soils and promote the growth of tea trees is of great practical significance to the sustainable development of the tea industry.In this study,2-and 10-year-old acidified tea garden soils were used as research objects.With the help of modern analytical techniques such as carbon and nitrogen element analyzer,continuous flow analyzer,high-throughput sequencing platform and real-time fluorescence quantitative PCR,combined with grey correlation analysis,redundancy analysis and variance decomposition analysis,the effects of biochars modified with potassium,calcium and magnesium on soil acidity(p H,exchangeable acid,exchangeable H⁺,exchangeable Al³⁺),base ion content(Ca²⁺,Mg²⁺,K⁺,Na⁺),available nutrients（available nitrogen,available phosphorus,available potassium）and its dynamic changes in different acidified tea gardens during the growth period of tea plant was studied.In order to provide a theoretical basis for the scientific improvement of acidified tea garden soil,the effects on the composition and diversity of soil microbial community and the growth of tea trees（nutrient absorption and root growth）were investigated.The main results are as follows:1.The application of modified biochar can significantly alleviate soil acidification in tea gardens.The p H of acidified tea garden soil was increased by 0.20-0.29 units on average during the growth period of tea trees,and the effect of modified biochar was similar to that of raw biochar.The exchangeable acidity(exchangeable Al³⁺and exchangeable H⁺)of the soil was reduced by 15.33%-20.07%on average during the growth period of tea trees treated by modified biochar,and the effect was better than that of raw biochar.In conclusion,the application of modified biochar significantly increased the p H of acidified tea garden soil,reduced the soil’s exchangeable acidity(exchangeable Al³⁺and exchangeable H⁺),and had a better effect on alleviating soil aluminum toxicity than ordinary biochar.2.The application of modified biochar increased the content of base ions in acidified tea garden soil.The contents of exchangeable K,Na,Ca,and Mg in theacidified tea garden soils were increased by the modified biochars,but the improvement effect was different from that of raw biochar.The average increase of exchangeable K in soil of KB treatment（Apply KOH modified biochar）was 21.90%-33.51%during the growth period of tea tree,and the improvement effect was better than that of B treatment（Apply Ordinary biochar）.The exchangeable Ca and Mg contents of soil under CMB treatment（Apply Ca/Mg modified biochar）increased by 10.12%-21.59%and 9.75%-26.94%,respectively,which were better than that under B treatment.The effect of modified biochar treatment on soil exchangeable sodium ions was similar to that of the raw biochar.In conclusion,the application of modified biochar increased the content of base ions in soil,and the KB and CMB treatments had better effects on the improvement of exchangeable potassium and exchangeable Ca²⁺and Mg²⁺in soil than B treatment.3.The application of modified biochar affected the available nutrients of acidified tea plantation soil to varying degrees.The modified biochar treatments reduced the content of available nitrogen in acidified tea garden soil,and the effect was similar to that of common biochar treatment.The KB treatment increased soil available P content,and the effect was similar to that of the raw biochar treatment,while CMB treatment decreased soil available P content.In addition,the content of soil available K was increased by 45.54%-57.24%in the KB treatment during the growth period of tea tree,and the effect was better than that of raw biochar treatment.Therefore,the modified biochar affects the content of available N,P and K in soil,and KB has better effect on the content of available potassium in soil than the B treatment.4.The application of modified biochar significantly improved soil enzyme activity in acidified tea garden.During the growth period of the tea trees,the activities of urease,acid phosphatase andβ-glucosidase were increased by 7.51%-15.27%,11.31%-51.06%and 7.86%-88.03%,respectively,and the effects were better than those of raw biochar treatment.In conclusion,the application of modified biochar significantly increased the activities of urease,acid phosphatase andβ-glucosidase in acidified tea garden soil,promoted the transformation of nitrogen,phosphorus and carbohydrate in tea garden soil,and had a better effect than the raw biochar.5.The application of modified biochar affected soil bacterial and fungal communities to varying degrees.The modified biochar treatment increased the copy numbers of soil bacteria and fungi by119.10%-442.98%and 27.31%-104.23%in KB treatment,as well as46.16%-123.34%and 25.34%-32.92%in CMB treatment,respectively.The positive effect of the KB treatment was better than that of the B treatment.The modified biochar treatments increased Chao1 and Shannon index of bacteria in the acidified tea garden soil by29.16%-40.92%and 4.03%-8.17%,respectively.From the analysis of bacterial community structure in the acidified tea garden soil,biochar treatment increased the relative abundance of Actinobacteria and decreased the relative abundance of Bacteroidetes after 2 years,and the relative abundance of Bacteroidetes in the KB treatment was lower than that in the B treatment.The B and KB treatments increased the relative abundance of Proteobacteria and decreased the relative abundance of Firmicutes in the soil.However,the CMB treatment reduced the relative abundance of Proteobacteria.Biochar treatment decreased the relative abundance of Bacteroides,Brevundimonas and Conexibacter in tea garden soil after 2 years,and the relative abundance of Brevundimonas under modified biochar treatment was lower than that under the B treatment.The B treatment also reduced the relative abundance of soil Acidothermus.An increased the relative abundance of Sphingobacter was observed in the KB and CMB treatments,while the B treatment reduced the relative abundance of Proteobacteria in tea garden soil after 10 years.A significant reduction in the relative abundance of Firmicutes was recorded in the KB treatment.An increase in the relative abundance of Acidobacteria,and a decreased Proteobacteria and Firmicutes was observed in the CMB treatment.The relative abundance of Acidothermus was obtained in the B treatment in tea garden soil after 10 years.The KB treatment increased the relative abundance of Acidothermus,while CMB increased that of Occallatibacter.However,a decrease in the relative abundance of Acidothermus was similar to that of B treatment.The bacterial community structure of the acidified tea garden soil had a positive relationship with the soil exchangeable H⁺,exchangeable Al³⁺,available P,available K,exchangeable Ca²⁺and exchangeable Mg²⁺.The analysis of soil fungal community structure in acidified tea garden,biochar treatment revealed an increased the relative abundance of Mucoromycota after 2 years,and decreased the Basidiomycota.The relative abundance of Mucoromycota in the KB and CMB treatments was higher than that in the B treatment,and the relative abundance of Basidiomycota in CMB treatment was lower than that in B treatment.Biochar treatment increased the relative abundance of Ascobolus in tea garden soil for two years,and KB and CMB treatment had the same effect as the B treatment.The KB and CMB treatments increased the relative abundance of Trichoderma,while CMB treatment increased the relative abundance of Aspergillus.Biochar treatments increased the relative abundance of Mucoromycota in tea garden soil after 10 years,and the KB and CMB treatments had the same effect as the B treatment.A reduction in the relative abundance of Basidiomycota was observed in the B treatment.The KB treatment increased the relative abundance of Mortierellomycota,while a decrease was observed in the CMB treatment..Biochar treatments increased the relative abundance of the Saitozyma,and KB and CMB treatments were better than the B treatment.In addition,the KB treatment also increased the relative abundance of Trichoderma.The community structure of soil fungi in acidified tea garden was positively correlated to soil exchangeable H⁺,exchangeable Al³⁺,available K,exchangeable Ca²⁺and exchangeable Mg²⁺.6.The application of modified biochar promoted the growth of tea tree roots and the absorption of N,P and K nutrients in the tea plants.The root weight of the tea plants treated with modified biochar increased by20.91-51.17%on average,with a more positive impact obtained in the CMB treatment than in the B treatment.The N,P and K uptake of tea trees increased by 7.28%-38.46%,15.51%-91.49%and 12.17%-65.29%,respectively.Notably,a higher N uptake was recorded in the KB and CMB treatments than in the B treatment.There was significantly higher uptake of P and K in the KB treatment than in the B treatment.N uptake was mainly affected by soil available nitrogen,root dry weight and exchangeable Al³⁺,and was mainly determined by the soil available N and its interaction with root weight in acidified tea garden.The uptake of P in the tea trees was mainly influenced by the soil available P,root weight and Penicillium,and was mainly determined by available P and its interaction with Penicillium.The uptake of K in the tea tree was mainly affected by the soil available K,root weight and fungal Chao1 index,and was mainly determined by the interaction of soil fungal Chao1 index and available potassium.