Magnesium-modified biochar improves tea quality and growth of tea plant by improving soil properties and promoting nutrient uptake

Magnesium-modified biochar improves tea quality and growth of tea plant by improving soil properties and promoting nutrient uptake | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Help Center Sign In Submit a Preprint Cite Share Download PDF Article Magnesium-modified biochar improves tea quality and growth of tea plant by improving soil properties and promoting nutrient uptake Yubo Luo, Ronghui Li, Xinhang Lv, Dubin Dong, Wenbin Liu, Pan Yang, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4373613/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Soil acidification affects the growth of tea plants and induces magnesium loss, which further reduces tea quality. In this study, magnesium-modified biochar was developed from discarded tea plant branches, via potting test to evaluate the effect on the red loam soil, and to study the quality of tea in acidified tea gardens. Four treatments were set up as control (no biochar added, CK), conventional magnesium fertilizer treatment (FC), tea plant branch biochar treatment (BC) and magnesium-modified biochar with acetic acid (BCY) respectively. Our results showed that soil pH was significantly increased by 0.3 and 0.42 units in BC and BCY treatments respectively, conventional magnesium fertilizer, biochar, and magnesium-modified biochar treatments could significantly increase soil organic matter, alkaline-dissolved nitrogen, effective phosphorus, quick-acting potassium, and exchanged calcium and magnesium content in acidified tea plantations. Compared with CK treatment, both conventional magnesium fertilizer treatment and biochar treatment could increase the root dry weight and tea plant height to some extent; the SPAD values of tea fresh leaves of BC and BCY treatments were significantly higher than those of CK and FC treatments by 17.6, 37.6 and 6.4, 26.4, respectively; and the increase in accumulation of nitrogen, phosphorus, potassium, calcium, and magnesium in tea leaves of FC, BC, and BCY treatments compared with that of CK was 2.49~8.04 g·kg -1 , 0.19~0.49 g·kg -1 , 0.30~3.27 g·kg -1 , 0.26~0.50 g·kg -1 , and 0.15~1.45 g·kg -1 ; and SPAD value, tea polyphenols, water leachate, caffeine, and amino acid contents of tea leaves in BC and BCY treatments were significantly higher than CK treatment ( P < 0.05). Our study showed that magnesium-modified biochar improved the quality of tea significantly via enhancing the pH, organic matter and nutrient content of soil, increasing the uptake of nitrogen, phosphorus, potassium, calcium and magnesium in the tea plant, and ascending photosynthesis, The best results were obtained with magnesium chloride modified biochar (BCL) treatment. This study plays a guiding role for the improvement and nutrient supplementation of acidified soil in tea plantations and promotes the healthy development of tea plantation soil.. Earth and environmental sciences/Ecology/Agri ecology Biological sciences/Ecology/Agri ecology biochar magnesium-modified acidified tea garden soil nutrients tea nutrient absorption tea quality Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Tea plant is one of the important cash crops, and the area planted of china ranks first in the world 1 . According to data from the National Bureau of Statistics 2 , in 2020 China's tea plantation area of 3,216,700 hectares accounted for 62.1% of global tea plantation area and tea production was 2,931,800 tons and represented 46.77% of global tea production. This represented increases of 66.51 and 100.46% than that of 10 years ago 3 . Soil Mg availability is thus related to tea plant growth and tea quality 4 . In addition, the optimum pH range for tea plants is 4.5 to 6.0, and the growth of tea plant was inhibited when pH<4.0 5 . Soil acidification can also be detrimental by increasing exchangeable aluminum (Al 3+ ) from the soil 6 . Accumulation of Al in tea garden soils can also interchange with Mg soil colloids resulting in Mg leaching losses that adversely affects the tea plant growth 5 and limits tea yields and quality 7 . In addition, soil acidification leads to changes in soil microbial communities and reduces the decomposition rates of soil organic matter and adversely alters soil ecosystem health 8 . Soil acidification in tea plantations has been increasing due to a large number of high-intensity anthropogenic activities and an estimated 52% of tea plantation soils possess pH values < 4.5 9 . This has been the result of the acidification effects of chemical fertilizers (especially nitrogen fertilizers) put into the tea plantation soils and increases Mg leaching 10 . Soil Mg content was lower than 50 mg kg - 1 in 73% tea gardens in China 11 . These red soil hilly areas in southern China cause strong leaching due to the warm and humid rainy climate and when coupled with the large amount of nitrogen fertilizers applied, leads to soil acidification, soluble Mg loss and a decline in the effective Mg content and reservoir 12 . Therefore, there is an urgent need to explore suitable amendments to alleviate and repair acidified tea garden soils and to increase soil Mg content to meet the Mg nutritional requirements of tea plants. Biochar is a novel soil conditioner and possesses unique physicochemical properties that promote soil structure and overall health. Biochar was found to be superior in enhancing tea garden soil buffering capacity and long-term applications increased the soil pH of tea garden soils 13 . The application of biochar in acidic red loam tea garden soil also effectively improved soil buffering and microbial activity and these were conducive to soil nutrient transformations 14 . Conventional biochar has certain limitations due to its own properties and the by-products produced during the pyrolysis process. These included a smaller specific surface area and a limited number of surface functional group species 15 . Physical, chemical and biological methods have been used to modify traditional biochar to improve biochar efficiency. These treatments increased the specific surface area resulting in an increased number of surface adsorption sites and further improved its adsorption capacity for pollutants such as heavy metals and reactive aluminum 16 . In addition, biochar modified by impregnation with metal salt solutions resulted in metal oxide attachment to its surface that could effectively increase the content of soil salt-based ions after application and further increase the soil's ability to retain and supply fertilizer 17 . For instance, montmorillonite could be modified using Fe and Al and sludge-based biochar with Mg salt impregnation. These treatments increased the efficiency of adsorptive properties and enhanced catalytic activity 18 , 19 . There are few studies on the application of magnesium-modified biochar for tea plantations. Therefore, we investigates the effect of magnesium-modified biochar on soil nutrient content and tea quality in tea plantations, and introduces magnesium ions needed for the growth and development of tea plants at the same time of soil improvement, which provides more choices of materials for acidified soil improvement and improves tea quality. Results Effect on root dry weight and plant height of tea plants The results in Fig. 1 showed that both conventional magnesium fertilizer and biochar treatments could increase the root dry weight and plant height of tea plant to some extent compared with CK treatment. The root dry weight of tea plant in BC and BCY treatments was significantly increased by 16.67% and 57.41%, respectively, compared with the CK treatment (P 0.05).The root dry weight of tea plant in FC, BC and BCY treatments was significantly increased by 4.11%, 8.22% and 10.49%, respectively, compared with the CK treatment and BCY treatments significantly increased tea plant plant height by 4.11%, 8.22% and 10.49%, respectively, compared with CK treatment ( P < 0.05). It can be seen that acidified tea garden species adding conventional magnesium fertilizer and biochar can promote tea plant root system and tea plant growth to a certain extent, in which the application of biochar on the tea plant root growth is significantly better than the conventional application of magnesium fertilizer, and the application of magnesium-modified biochar on the root system of the tea plant and the growth of the tea plant are better than the application of common biochar to promote the effect of the tea plant root system and the growth of the tea plant.. Effect on soil pH and organic matter in tea plantations The effects of different treatments on soil pH and organic matter in tea plantations are shown in Fig. 2 , BC and BCY treatments to tea plantation soils both increased soil pH and organic matter content, and the soil pH of conventional magnesium fertilizer treatment was lower than that of the control; the highest soil pH was found in the BCY treatment, and the soil pH of BC and BCY treatments was significantly increased by 0.3 and 0.42 units, respectively( P 0.05). The effect of different treatments on the enhancement of soil organic matter content in tea plantations was BC > BCY > FC, and the soil organic matter content of tea plantations in BC and BCY treatments was significantly higher than that in CK treatment by 28.04 and 22.93 g·kg - 1 ( P < 0.05). Thus, the application of biochar and magnesium-modified biochar in tea garden soil could significantly increase soil pH and organic matter content, thus slowing down the acidification of tea garden soil and providing a long-term source of organic carbon for the soil, in which the effect of magnesium-modified biochar in increasing soil pH was better than that of ordinary biochar. Effect on soil nutrient content in tea plantations Adding BC and BCY treatments could improve the nutrient content of tea garden soil to a certain extent, and the alkaline nitrogen content of tea garden soil in BC and BCY treatments was increased by 3.04 mg·kg - 1 and 1.27 mg·kg - 1 compared with CK treatment(Table 1 ); FC、BC and BCY treatments could all increase the effective phosphorus and quick-acting potassium content of tea garden soils, and the effective phosphorus content of FC, BC and BCY treated soils was significantly higher than that of the CK treatment by 6.19 mg·kg - 1 , 12.60 mg·kg - 1 and 23.06 mg·kg - 1 , respectively ( P < 0.05);Soil quick potassium content was increased by 1.87 mg·kg - 1 in FC treatment and significantly increased by 14.39 mg·kg - 1 and 5.00 mg·kg - 1 in BC and BCY treatments, respectively, over CK treatment ( P < 0.05).. Table 1 Effect on soil nutrient content in tea plantations Treatment Soil nutrient content in tea garden N(mg/kg) P(mg/kg) K(mg/kg) CK 45.14 ± 1.67a 27.31 ± 1.28d 35.67 ± 0.84c FC 34.09 ± 4.71b 33.50 ± 1.05c 37.54 ± 1.84b BC 48.18 ± 1.40a 39.91 ± 2.22b 50.06 ± 3.19a BCY 46.41 ± 2.79a 50.37 ± 1.05a 40.67 ± 0.88b Note : Different lowercase letters in the same column indicate significant differences between treatments ( P < 0.05 ), the same below. Effect of different treatments on exchangeable calcium and magnesium in tea garden soil As can be seen from Fig. 3 : the soil exchangeable calcium content with added biochar and magnesium-modified biochar treatments was significantly higher than CK and FC treatments, and the soil exchangeable calcium content with BC and BCY treatments was significantly increased by 16.96% and 21.74% and 16.45% and 21.21%, respectively ( P < 0.05). The addition of magnesium-modified biochar to the tea garden soil could significantly increase the soil exchangeable magnesium content, and the BCY treatment had the highest soil exchangeable magnesium content of 4.71 cmol·kg - 1 ; the soil exchangeable magnesium content of the BCY treatment was significantly increased by 3.09 cmol·kg - 1 and 3.87 cmol·kg - 1 compared with that of the CK treatment and the BC treatment ( P < 0.05). It can be seen that both added biochar and magnesium-modified biochar can improve the soil exchangeable calcium and magnesium content of acidified tea plantations to a certain extent, while the effect of magnesium-modified biochar treatment in enhancing soil exchangeable magnesium content was more obvious.. Effect of different treatments on photosynthesis of tea plant The strength of photosynthesis of tea plant was indicated by the relative chlorophyll content (SPAD value) of tea fresh leaves, and the changes of SPAD value of tea fresh leaves in different treatments were shown in Fig. 4 . As can be seen from Fig. 4 , the size of SPAD value was BCY>BC>FC>CK, and conventional magnesium fertilizer and added biochar and magnesium-modified biochar treatments could significantly increase the SPAD value of tea plant fresh leaves, in which the SPAD value of tea plant fresh leaves of BC and BCY treatments were significantly higher than that of CK and FC treatments by 17.6, 37.6, and 6.4, 26.4, respectively ( P <0.05). It can be seen that conventional magnesium fertilizer and biochar addition can significantly increase the SPAD value of tea plant fresh leaves, promote the photosynthesis of tea plants in acidified tea plantations, and facilitate the accumulation of carbohydrates in tea leaves, among which the magnesium-modified biochar treatment has a better effect. Effect of different treatments on nutrient accumulation in tea leaves As shown in Table 2 , FC、BC and BCY treatments could promote the uptake of N, P, K, Ca and Mg nutrients in tea leaves; the increase in the accumulation of N in tea leaves of FC, BC and BCY treatments ranged from 2.49 to 8.74 g·kg - 1 compared with CK, in which the accumulation of N in tea leaves of BC and BCY treatments increased significantly by 11.33% and 18.43% ( P < 0.05); the accumulation of P in tea leaves of FC, BC and BCY treatments increased in the range of 0.19–1.44 g·kg - 1 , of which the accumulation of P in tea leaves of BCY treatment increased significantly by 16.61% ( P < 0.05); Compared with CK, the increases of K and Ca accumulation in tea leaves of FC, BC and BCY treatments were 0.30–3.27 g·kg - 1 and 0.26–0.84 g·kg - 1 , and the K and Ca accumulation in tea leaves was highest in BCY treatment, and the differences of Ca accumulation in tea leaves among treatments did not reach the significant level; Magnesium-modified biochar treatment was able to significantly increase tea Mg accumulation compared with other treatments, and tea Mg accumulation increased significantly by 57.09% in BCY treatment compared with CK. It can be seen that conventional magnesium fertilizer, added biochar and magnesium-modified biochar can all promote the uptake of N, P, K, Ca and Mg nutrients in tea leaves, thus promoting the growth of tea plants, of which the comprehensive results of magnesium-modified biochar treatment had the best effect. Table 2 Difference analysis of nutrient accumulation in tea Treatment Nutrient accumulation of tea(g/kg) N P K Ca Mg CK 43.62 ± 2.08d 2.95 ± 0.47c 4.45 ± 0.21c 8.77 ± 0.45a 2.54 ± 0.11b FC 46.11 ± 1.01cd 3.14 ± 0.05bc 4.75 ± 0.20bc 9.03 ± 0.83a 2.69 ± 0.17b BC 48.59 ± 1.72bc 3.26 ± 0.05bc 4.95 ± 0.05b 9.22 ± 0.02a 2.76 ± 0.06b BCY 51.66 ± 1.58ab 3.44 ± 0.13a 7.72 ± 0.22a 9.27 ± 0.17a 3.99 ± 0.32a Effect of different treatments on the main quality components of tea leaves As shown in Table 3 , FC、BC and BCY treatments could affect the tea quality, and the tea polyphenol content of tea leaves showed BC>BCY>FC, of which the tea polyphenol content of tea leaves in BC treatment was the highest (16.53%), which was significantly higher than that of CK and FC treatments ( P <0.05); Compared with the CK treatment, the caffeine and amino acid contents of tea leaves of BCY, BC and FC treatments were significantly increased by 39.04%, 30.93%, 14.71% and, 15.81%, 15.20% and 12.16%, respectively ( P < 0.05). The variation of water leachate content of tea leaves in different treatments ranged from 37–48%. Conventional magnesium fertilizer, added biochar and magnesium-modified biochar could increase the water leachate content of tea leaves to different degrees, and added magnesium-modified biochar BCY treatment increased the water leachate significantly by 25.16% compared with the CK treatment ( P BC>BCY>FC, and the lowest phenol-ammonia ratio of tea leaves in BCY treatment with magnesium-modified biochar was significantly lower than that in CK treatment. In conclusion, adding BC and BCY treatments can improve the content of various quality components of tea, in which the effect of improving the quality of tea is more obvious with the addition of magnesium-modified biochar BCY treatment. Table 3 Difference analysis of main quality components content of tea Treatment Main Quality Components of Tea tea polyphenol(%) caffeine(%) amino acid(%) water extracts(%) phenol ammonia CK 15.54 ± 0.42b 3.33 ± 0.15c 3.29 ± 0.10c 37.59 ± 1.26b 4.47 ± 0.22a FC 15.53 ± 0.25b 3.82 ± 0.13b 3.69 ± 0.06b 39.22 ± 0.31b 4.21 ± 0.03b BC 16.53 ± 0.22a 4.36 ± 0.18a 3.79 ± 0.06ab 43.66 ± 1.45b 4.36 ± 0.02b BCY 16.51 ± 0.61a 4.63 ± 0.16aa 3.81 ± 0.05a 47.05 ± 1.65a 4.32 ± 0.11b Discussion Effect of magnesium-modified biochar on the improvement of acidified tea plantation soil The optimal pH range for tea plant growth is 4.5 to 6.0, and our study showed that the application of biochar could increase the pH of acidified tea plantation soil. Biochar is alkaline and contains alkaline groups, which can neutralize the H + contained in the soil solution after being applied to the soil, which is consistent with the results of Xie and Wu 21 , 22 . Biochar is a carbon-containing material with a porous structure and stable, and the pH of the tea garden soil decreased significantly after a long period of time in the potting experiment, which may be related to the fact that the nitrogen in the organic matter was converted by the microorganisms into ammonia nitrogen and ammonium root ions (NH 4 + ) and further nitrified to release H + 23 . We also found that BCY treatment was more effective than BC treatment in increasing the pH of acidified tea plantation soil, which was attributed to the fact that BCY treatment was introduced with compounds (magnesium oxide, etc.) in the process of preparation, which were able to form more chemical bonds with the biochar indicating that the magnesium-modified biochar had a higher specific surface area, contained soluble alkaline matrix substances 24 , which could adsorb the H + in the soil solution and increase soil salt-based ion content 25 . Organic matter is an important component of soil, which contains various nutrients needed for plant growth and plays a very important role in soil fertility and sustainable agricultural development 26 . Some studies have shown that the direct addition of crop residues 27 , organic fertilizers, and other agricultural and forestry waste organic matter to the soil 28 . Biochar can increase soil organic carbon content 29 . In this experiment, the biochar applied to the soil of acidified tea plantation, which itself belongs to the biomass material with high carbon content, was directly applied to the soil of tea plantation which is equivalent to the direct input of a large amount of organic carbon into the soil, which is conducive to the effect of increasing the accumulation of soil organic matter. This is similar to the results of many studies, such as Li 30 , which showed that both rice and corn stover charcoal could improve the acidity of red loamy rice soil, and increase soil organic carbon and soil nutrient content. Xu 31 found that soil application of biochar could increase the total soil carbon stock of moso bamboo forests, thus promoting the carbon sequestration capacity of moso bamboo forest ecosystems through long-term field experiments in moso bamboo forests. As a carbon-rich biomass material, biochar plays a significant role in sequestering carbon and increasing sinks 32 . Soil nutrient content is a direct source of nutrient uptake for tea plant growth, and some studies have shown that the application of biochar can significantly increase soil nutrient content 33 . This study showed that BC and BCY treatment increased the alkaline dissolved nitrogen content of tea garden soil compared with CK treatment, indicating that soil addition of biochar may promote the mineralization of soil organic nitrogen, thus releasing inorganic nitrogen 34 . In addition, it has been found that soil addition of biochar reduces leaching and volatilization loss of soil nitrogen, thus increasing soil nitrogen content 35 . In this study, it was found that both BC and BCY treatment could increase the effective phosphorus content of tea garden soils, which was attributed to the fact that, on the one hand, the solubility of PO 4 3- was low in the more acidic soil conditions, and the biochar increased the soil pH thereby promoting the dissolution of PO 4 3- in the soil 36 ; on the other hand, the biochar itself carried phosphorus, which was released by adding it to the soil thereby increasing the effective phosphorus content of the soil 37 . Changes in soil quick potash in tea plantations may be related to changes in soil pH in tea plantations 38 , and the results of this study showed that all biochar treatments increased soil quick potash content, the reason for this is because biochar itself contains a certain amount of potassium, so that the application of all biochar increased soil quick potash content in tea plantations 39 . Soil exchangeable calcium and magnesium is an important component of soil salt-based substances and is a very important chemical property of soil 40 . In this study, both BC and BCY treatment could increase the soil exchangeable calcium and magnesium content of acidified tea plantations to a certain extent, which could be attributed to the fact that biochar contains a large number of salt-based ions, which were added to the soil to increase the soil exchangeable calcium and magnesium content on the one hand 41 , and on the other hand, it might be due to the fact that the soil acid solubilization promotes certain soil minerals to release salt-based ions 42 . This study also found that the addition of BCY treatment to the soil significantly increased the soil exchangeable magnesium content 43 , suggesting that the magnesium element loaded on the biochar was converted into exchangeable Mg 2+ in the soil, similar to the results of other studies on the amelioration of soil acidification 44 . Dai 45 found that modified biochar prepared by mixing raw materials could increase the pH, salinity ions and pH buffering properties of the soil, as well as reduce the exchangeable aluminum concentration of the soil. Qin 46 used magnesium-modified biochar for indoor soil simulation tests and found that magnesium-modified biochar prepared at different pyrolysis temperatures not only had larger porosity but also had more -OH and -COOH functional groups compared with unmodified biochar, which could reduce the soil acidity and at the same time, effectively improve the soil fertility, soil exchangeable calcium and magnesium content. For tea garden soils with high acidification and low organic matter content, using the qualities of magnesium-modified biochar for amendment can significantly reduce soil acidity 47 and increase the organic matter content of acidified tea garden soils 48 , 49 while also increasing soil nutrient content 50 , so that the tea garden soils develop in the direction of being more conducive to the growth of tea plants, and improve the yield of tea gardens and the quality of tea leaves 51 , 52 . Effect of magnesium-modified biochar on the growth of tea seedlings and tea quality The addition of biochar improves soil acidity, increases soil organic matter content, and improves soil nutrient content so as to meet the nutrient demand of tea plant during its reproductive period 53 , and significantly enhances the absorption and accumulation of nitrogen, phosphorus, potassium, and calcium and magnesium nutrients in tea. Plant root system is an important organ for absorbing soil nutrients, and its growth and development will directly affect the absorption of soil nutrients by plants. In this experimental study, it was found that biochar in acidified tea garden soil could promote the growth of tea plant roots, which was due to the fact that on the one hand, biochar was able to improve soil acidity, reduce soil bulk weight, and increase soil aeration pore space 54 ; on the other hand, it was able to improve soil pH, salinity ions, and alleviate the toxic effect of aluminum in acidified soils, which in turn promoted the growth of tea plant roots 55 . This study also found that BCY treatment promoted the root growth of tea seedlings significantly better than BC treatment, which is because magnesium-modified biochar can increase the magnesium necessary for the growth of tea plants while alleviating aluminum toxicity, thus promoting the root growth and development of tea plants. In this study, BC and BCY treatment could promote the uptake of nitrogen, phosphorus, potassium, and calcium and magnesium nutrients in tea leaves to different degrees, and tea plant is an ammonium-loving plant, and the addition of biochar significantly increased the supply of alkaline dissolved nitrogen (ammonium nitrogen) in the soil, which promoted the uptake of nitrogen by tea plant 56 ; Magnesium is an important component of tea plant chlorophyll and affects tea plant leaf photosynthesis 57 , due to the addition of biochar increased the effective magnesium content of acidified tea garden soil, promoting the absorption of magnesium by tea plants and the synthesis of tea chlorophyll, thus enhancing tea photosynthesis. In this study, magnesium-modified biochar, because of its large magnesium loading, was added to the soil to significantly increase the absorption of magnesium by tea plants, significantly increase the SPAD value of the fresh leaves of tea plants in acidified tea gardens, and contribute to the promotion of photosynthesis and the synthesis of carbohydrates in tea leaves. Tea garden soil nutrient content directly affects the growth and development of tea plants, which in turn affects the quality of tea, tea quality is generally determined by the tea polyphenols, caffeine, amino acids, water leachate and phenol-ammonia ratio and other indicators 58 . Tea polyphenol consists of various phenolic compounds, mainly affects the aroma and taste of tea, tea unique tea flavor and sweetness from tea polyphenol, tea polyphenol content is appropriate at about 20%, too high will lead to tea bitterness and astringency directly affect the quality of tea 59 . In this study, the tea polyphenol content of all treatments ranged from 15.50–17.00%, and the addition of biochar was able to increase the tea polyphenol content, of which the tea polyphenol content of BCY treatment was the highest and significantly higher than that of the CK and FC treatments ( P < 0.05). This is due to the fact that tea polyphenol content is closely related to the nutrients (nitrogen, phosphorus and potassium) in tea leaves, and an increase in the accumulation of nitrogen, phosphorus and potassium nutrients increases the tea polyphenols synthesized by the tea plant 60 . The study of Jiang 61 found that the application of biogas and biochar can increase the amino acid content of tea and help to improve the quality of tea, which is the same as the results of this study. Caffeine and amino acids are important substances for the freshness of tea broth, and water leachate is important for the strong flavor of tea broth 62 . The results of this study showed that BC and BCY treatment could increase the content of caffeine, amino acids and water leachate in tea, and the magnesium-modified biochar enhancement effect was significantly better than that of unmodified biochar, which could make the tea broth fresh and refreshing, with a high and long aroma, and better quality. Materials and Methods Soil Information The test soils were taken in June 2022 from a tea plantation base in Lin'an District, Hangzhou City, Zhejiang Province, which was planted with tea plants for 10 years. The area has a subtropical monsoon climate with an annual average temperature of 15.9℃, an average annual precipitation of 1420 mm and a red loam soil texture. Soil samples were taken according to the "S" type multi-point mixed collection at 0 ~ 20 cm depths, air-dried followed by stone and dead leave removal. The soil was then ground and passed through a 2 mm sieve and used for basic chemistry testing (Table 4 ). Table 4 Basic physical and chemical properties of tea plantation soil used in these experiments pH Organic matter (g kg − 1 ) Available N (mg kg − 1) ) Available P (mg kg − 1 ) Available K (mg kg − 1 ) Exchangeable Mg (cmol kg − 1 ) red loam soil 4.51 12.3 32.93 27.67 67.33 0.78 Biochar preparation Discarded tea plant branches were collected, rinsed 2–3 times with distilled water then dried at ambient temperature. The branches were then crushed and pyrolyzed under anaerobic conditions at 500°C for 2h in a muffle furnace. This biochar was designated BC. Modified biochars were prepared using tea plant twig powder was homogeneously mixed with Mg(CH 3 COO) 2 (designated ‘Y’ treatment)solutions at 1 g:10 mL (Table 5 ). The mixtures were oscillated at frequency of 220 rpm at 30°C for 1 h, sealed and impregnated for 23 h, filtered, dried at 105°C, and placed in a muffle furnace and pyrolyzed under anaerobic conditions at 500°C for 2 h. The furnace was then allowed to cool to room temperature and the obtained product was ground and passed through a 100-mesh sieve to produce Mg-modified biomass charcoal (MgBC). Table 5 Biochar-modified salt solutions Serial number Modifier Concentration (M) BCY Mg(CH 3 COO) 2 1.5 Experimental design Four treatments were set up: control (no biochar added, CK), conventional magnesium fertilizer treatment (FC), tea plant branch biochar treatment (BC), and, magnesium acetate modified biochar (BCY), with three replications for each treatment. High-quality tea seedlings with good growth and basic uniform plant size were selected, and the seedlings were taken to ensure that the root system was intact and able to survive. Pour 5 kg of soil into the potting bowl, mix the biomass charcoal and soil (2%) thoroughly, fertilizer as a basal fertilizer applied at once, each potting bowl transplanted 4–6 tea seedlings, the first watering watered thoroughly, field water holding capacity to maintain 70%. Cultivation of the early need to be based on the survival of tea seedlings, there is a need to replenish seedlings, the 30th d of the test each pot of 1.25 g urea, usually potted tea plants in accordance with the daily management of the tea garden field, the experimental management measures of the treatment is the same. The entire treatment process for a total of 3 months, the collection of tea plant samples, tea seedlings with the root system complete take out and bring back to the laboratory, with deionized water to quickly wash the root system attached to the soil after the tea roots and stems and leaves are separated, the quality of tea sampling standards for the first bud and two leaves of the tea fresh leaves, packed into envelopes and marking, put into the oven at 105 ℃ to kill the green for 1h in 50 ℃ drying to constant weight, the plant samples placed in a pulverizer, and then dried to constant weight. The plant samples were ground in a pulverizer and sieved, and stored in plastic self-sealing bags for the determination of tea-related indexes. Soil samples were taken by broken ring sampling, soil samples were dried naturally, ground and sieved, and then stored for the determination of related indexes. Indicators and methods The analytical methods of soil samples were referred to Soil Agrochemical Analysis (Third Edition) 20 : soil pH was determined by potentiometric method with soil-water ratio of 1:2.5; soil organic matter was determined by volumetric method with externally heated potassium dichromate; effective soil phosphorus was determined by hydrochloric acid-ammonium fluoride dissolution-molybdenum antimony antimony colorimetry; quick-acting potassium of the soil was determined by ammonium acetate leaching and flame photometric method; alkaline nitrogen of the soil was measured by alkaline dissolution diffusion method Soil cation exchange capacity (CEC) was determined by 1 mol/L ammonium acetate exchange method; soil exchangeable salty ions were extracted by 1 mol/L ammonium acetate solution, and Ca and Mg in the extract were determined by atomic absorption spectrophotometry. Measurement of tea-related indexes: SPAD value of tea leaves in each treatment was determined by chlorophyll meter; total nitrogen of tea leaves was determined by carbon and nitrogen analyzer method; total phosphorus was determined by H 2 SO 4 -H 2 O 2 digestion-molybdenum antimony antimony colorimetry method; total potassium was determined by H 2 SO 4 -H 2 O 2 digestion-flame photometer method; total calcium and magnesium were determined by H 2 SO 4 -H 2 O 2 cooking-atomic absorption spectrophotometry was used for total potassium; total calcium and magnesium were used for total calcium and magnesium. Tea polyphenols were determined by the colorimetric method of forintol (GB /T 8313 − 2018); caffeine was determined by ultraviolet spectrophotometry (GB /T 8312 − 2013); free amino acids were determined by the colorimetric method of ninhydrin (GB /T 8314 − 2013); water extracts were determined by the boiling water extraction method (GB /T 8314 − 2013); water extracts were determined by the flame photometric method of HSO4H2O2 digestion and atomic absorption spectrophotometry. leachate was determined by boiling water extraction-weight method (GB /T 8305 − 2013). Statistical analyses One-way analysis of variance (ANOVA) was performed using IBM SPSS Statistics 23 software. Duncan’s method was used to make multiple comparisons of the experimental data. The significance level of the difference was P < 0.05 using Origin 2021. The experimental data were expressed as mean ± standard deviation (SD). Research involving plants statement Experimental research and feld studies on plants (either cultivated or wild), including the collection of plant material, comply with relevant institutional, national, and international guidelines and legislation. Tea trees purchased by Zhejiang A&F University, Plant samples are stored in the School of Environment and Resources, Zhejiang A&F University Conclusions Our study revealed the effects of magnesium-modified biochar on soil nutrient content and tea quality in acidified tea gardens. Biochar (both ordinary Biochar, magnesium-modified biochar) could improve soil pH and soil organic matter and our study showed that magnesium-modified biochar improved the quality of tea significantly via enhancing the pH, organic matter and nutrient content of soil, increasing the uptake of nitrogen, phosphorus, potassium, calcium and magnesium in the tea plant, and ascending photosynthesis, The best results were obtained with BCY treatment. This study plays a guiding role for the improvement and nutrient supplementation of acidified soil in tea plantations and promotes the healthy development of tea plantation soil. Declarations Funding This work was financed by the National Natural Science Foundation of China (32371543), Zhejiang High-level Talents Special Support Program (2020R52026), Research and Science Development Fund of Zhejiang A&F University(2023FR012). Institutional Review Board Statement No humans or animals were involved in this study. Informed Consent Statement Not applicable. Data Availability Statement The datasets generated and/or analysed during the current study are not publicly available due [For the sake of privacy of the individuals and team labs involved in the research] but are available from the corresponding author on reasonable request. Conflicts of Interest The authors declare no conflict of interest. References Hu C. et al. Current Status and Health Risk Assessment of Heavy Metals Contamination in Tea across China[J]. Toxics, 2023, 11(8): 662. Yan P. et al . Soil acidification in Chinese tea plantations[J]. Science of The Total Environment, 2020, 715: 136963. Hou R. et al . Sustainable Tea Garden Ecotourism Based on the Multifunctionality of Organic Agriculture Based on Artificial Intelligence Technology[J]. Mobile Information Systems, 2021, 2021: 8696490. Zhang Y. et al . Effects of Magnesium on Transcriptome and Physicochemical Index of Tea Leaves[J]. Plants, 2023, 12(9): 1810. Tseng W-Y. et al . Comprehensive Analysis Revealed the Specific Soil Properties and Foliar Elements Respond to the Quality Composition Levels of Tea (Camellia sinensis L.)[J]. Agronomy, 2022, 12(3): 670. Pan X-Y. et al . Characteristics of crop straw-decayed products and their ameliorating effects on an acidic Ultisol[J]. Archives of Agronomy and Soil Science, 2021, 67(12): 1708-1721. Kunito T. et al . Aluminum and acidity suppress microbial activity and biomass in acidic forest soils[J]. Soil Biology and Biochemistry, 2016, 97: 23-30. Joris H A W. et al . Effects of soil acidity and water stress on corn and soybean performance under a no-till system[J]. Plant and Soil, 2013, 365(1): 409-424. Yi X. et al . Organic amendments improved soil quality and reduced ecological risks of heavy metals in a long-term tea plantation field trial on an Alfisol[J]. Science of The Total Environment, 2022, 838: 156017. Arafat Y. et al . Long-Term Monoculture Negatively Regulates Fungal Community Composition and Abundance of Tea Orchards[J]. Agronomy, 2019, 9(8): 466. Wu X. Development of famous tea and application of magnesium fertilizer in tea plantations[J]. Tea Newsletter, 1994(3): 11-13. Zhu Y. et al . Magnesium nutrition in red soil tea plantations in southern hills[J]. Tea Science, 2000(2): 95-100. Wang Y. et al . Effects of biochar on soil properties and fungal community structure in acidified tea plantations[J]. Tea Science, 2021, 41(3): 419-429. Zheng H. et al . Application of biochar to improve microbial characteristics and enzyme activities of acidic red soil tea plantation soils[J]. China Soil and Fertilizer, 2019(2): 68-74 Bardestani R. et al . Steam activation and mild air oxidation of vacuum pyrolysis biochar[J]. Biomass and Bioenergy, 2018, 108: 101-112. Azargohar R. et al . Steam and KOH activation of biochar: Experimental and modeling studies[J]. Microporous and Mesoporous Materials, 2008, 110(2): 413-421. Huang C. Effects of common biochar and acid-modified biochar on soil water-salt distribution and spinach growth in mudflat area[D]. Yangzhou University, 2021. Luo J. et al . Characterization and catalytic performance of iron-aluminum column-supported acidified montmorillonite catalysts[J]. Industrial Catalysis, 2017, 25(1): 54-57. Yang Y. et al . Removal of phosphorus and antibiotics from water by magnesium-modified sludge-based biochar[J]. China Environmental Science, 2022, 42(9): 4137-4144. Bao S. Soil agrochemical analysis [M]. Beijing, China Agricultural Press, 2000. Xie G. et al . Effects of biochar amendment on degraded vegetable soil[J]. Journal of Southern Agriculture, 2014, 45 (1): 67-71 Wu M. et al . Effects of biochar on soil acidity and exchange capacity in rubber plantation[J]. China Agricultural Science and Technology Review, 2017,19 (3): 98-107. Wang N. et al . Effects of three plant materials on the improvement of soil acidity in two tea gardens[J]. Soil, 2009,41 (5): 764-771. Yuan J-H. et al . Effects of biochars generated from crop residues on chemical properties of acid soils from tropical and subtropical China[J]. Soil Research, 2012, 50(7): 570. Wang Y. et al . Study on the improvement effect of biochar on soil acidity in strong acid tea garden[J]. China Agricultural Bulletin, 2018,34 (12): 108-111. Sun K. et al . Effects of different organic materials application on phosphorus accumulation and transformation in vegetable field[J]. Environmental Science: 1-15. Liang B. et al . Black carbon affects the cycling of non-black carbon in soil[J]. Organic Geochemistry, 2010, 41(2): 206–213. Kong J. et al . Effects of straw addition on soil nitrogen dynamics under simulated freeze-thaw cycles[J]. Journal of Shenyang Normal University (Natural Science Edition), 2022, 40 (6): 527-534. Meng Y. et al . Integrated analysis of the effects of biochar application on soil aggregates and organic carbon in farmland [J]. Environmental Science: 1-13. Li M. et al . Effects of different straw biochars on nutrients and microbial community structure in red paddy soil [J]. China Agricultural Sciences, 2015,48 (7): 1361-1369. Xu L. et al . Biochar application increased ecosystem carbon sequestration capacity in a Moso bamboo forest[J]. Forest Ecology and Management, 2020, 475: 118447. Jiang F. et al . Effects of biochar on soil physical and chemical properties and tea yield in tea garden[J]. Acta Tea Sinica, 2015,56 (1): 16-22. Zhang S. et al . Research progress on soil acidification in tea garden [J]. Tea, 2019, 45 (1): 17-23. Lehmann J. et al . Biochar for environmental management: An introduction[J]. Biochar for Environmental Management: Science and Technology, 2009: 1–12. Lehmann J. et al . Nutrient availability and leaching in an archaeological Anthrosol and a Ferralsol of the Central Amazon basin: fertilizer, manure and charcoal amendments[J]. Plant and Soil, 2003, 249(2): 343–357. Zhao X. et al . Does Biochar Addition Influence the Change Points of Soil Phosphorus Leaching?[J]. Journal of Integrative Agriculture, 2014, 13: 499–506. Zhai L. et al . Short-term effects of maize residue biochar on phosphorus availability in two soils with different phosphorus sorption capacities[J]. Biology and Fertility of Soils, 2015, 51(1): 113–122. Deng X. et al . pH and main nutrient characteristics of tobacco-planting soil in Xiangxi and their relationship[J].Soil, 2017,49 (1): 49-56. Liu M. et al . Effects of different biochars on soil nutrients and nitrogen use efficiency in aeolian sandy soil[J]. China Soil and Fertilizer, 2023 (5): 20-27. Yu Y. et al . Distribution characteristics of soil cation exchange capacity and exchangeable base ions in Ehuangzhang Mountain Rainforest [J]. Soil Bulletin, 2022,53 (6): 1341-1349. Zheng M. et al . Effects of biochar addition on soil base ion leaching under simulated acid rain[J]. Journal of Agricultural Environmental Sciences, 2021, 40 (1): 163-173. Ling D. et al . Effects of simulated acid rain on the migration and release of base cations in latosol[J]. Soil Science, 2007 (3): 444-450. Kramer R W. et al . Identification of Black Carbon Derived Structures in a Volcanic Ash Soil Humic Acid by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry[J]. Environmental Science & Technology, 2004, 38(12): 3387–3395. Xue X. et al . Effects of potassium and magnesium interaction on growth and nutrient uptake of rubber seedlings[J]. Acta Nutrienta Planta Sinica, 2020, 26 (10): 1870-1878. Dai Z. Research on the amelioration effect and biochemical mechanism of biochar on acidified soil [D]. Zhejiang University, 2017. Qin J. Preparation of magnesium-modified biochar with different pyrolysis temperatures and its effects on soil chemical properties and enzyme activities [D]. Guangxi University, 2021. Wang J. et al . A soil management strategy for ameliorating soil acidification and reducing nitrification in tea plantations[J]. European Journal of Soil Biology, 2018, 88: 36–40. Le V S. et al . How application of agricultural waste can enhance soil health in soils acidified by tea cultivation: a review[J]. Environmental Chemistry Letters, 2022, 20(1): 813–839. Hu Y. et al . Effects of biochar on CO2 and N2O emissions and microbial characteristics in tea garden soil[J]. Applied Ecology, 2015, 26 (7): 1954-1960. Xu L. Preparation and properties of magnesium-loaded biochar composites [D]. Hebei Normal University of Science and Technology, 2022. Sun Y. et al . Effects of biochar on soil improvement and tea quality in tea garden[J]. China Soil and Fertilizer, 2017 (6): 9-14. Wu Z. et al . Effects of biochar amendment on acidified tea garden soil[J]. Fujian Agricultural Journal, 2012, 27 (2): 167-172. Wang F. et al . Effects of biochar combined with nitrogen fertilizer on tea plant growth and nitrogen use efficiency[J]. Tea Science, 2018, 38 (4): 331-341. Li C. et al . Effects of bulk density of subsoil on root growth and absorption activity of maize[J]. China Agricultural Sciences, 2005 (8): 1706-1711. Liang X. et al . Effects of biochar on root growth and physiological characteristics of quinoa in saline-alkali land[J]. Shandong Agricultural Sciences, 2020,52 (12): 24-29. Wang L. et al . Effects of biochar and combined application with organic fertilizer on growth, nitrogen uptake and quality of Guixiang 22 tea plant[J]. Tropical Agricultural Sciences, 2018, 38 (6): 18-24 + 48. Han W. et al . Development of tea garden soil main nutrient obstacle factors and series of tea plant special fertilizer[J]. Tea Science, 2002 (1): 70-74 + 65. Liu W. et al . Compared the effects of different microbial fertilizers and chemical fertilizers on soil fertility and tea quality in tea gardens[J]. Soil and Fertilizer in China, 2023 (6): 78-86. Li C. et al . Effects of biochar-based fertilizer on soil nutrients and tea yield and quality in acidified tea garden[J]. Soil Bulletin, 2021, 52 (2): 387-397. Li J. et al . Effects of fertilization patterns on tea nutrient accumulation and soil fertility[J]. Jiangsu Agricultural Sciences, 2019, 47 (7): 170-174. Jiang Y. Effects of biogas slurry and biochar application on soil and tea quality in tea garden[D]. Zhejiang University of Science and Technology, 2023. Yi X. et al . Analysis of main quality components of black tea from different producing areas[J]. Tea Newsletter, 2017, 44 (2): 30-33. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4373613","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":303307160,"identity":"b7613cbd-db2b-468b-b550-a90a55fc4ed9","order_by":0,"name":"Yubo Luo","email":"","orcid":"","institution":"Zhejiang A\u0026F University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yubo","middleName":"","lastName":"Luo","suffix":""},{"id":303307161,"identity":"fca6bb3a-ac78-4a72-9dc8-f565bc85eaa9","order_by":1,"name":"Ronghui Li","email":"","orcid":"","institution":"Agricultural and Rural Bureau of Qu Zhou","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Ronghui","middleName":"","lastName":"Li","suffix":""},{"id":303307162,"identity":"f81f1d5f-d4a5-41ec-9c7e-391df40cc713","order_by":2,"name":"Xinhang Lv","email":"","orcid":"","institution":"Zhejiang A\u0026F University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Xinhang","middleName":"","lastName":"Lv","suffix":""},{"id":303307163,"identity":"56da8f41-fb3d-45af-9f38-6ef8e84d2d80","order_by":3,"name":"Dubin Dong","email":"","orcid":"","institution":"Zhejiang A\u0026F University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Dubin","middleName":"","lastName":"Dong","suffix":""},{"id":303307164,"identity":"65436566-bed2-4d2b-91d3-f5d165078f17","order_by":4,"name":"Wenbin Liu","email":"","orcid":"","institution":"Zhejiang A\u0026F University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Wenbin","middleName":"","lastName":"Liu","suffix":""},{"id":303307165,"identity":"ee07a765-4087-4d83-b717-51b1f77e40ac","order_by":5,"name":"Pan Yang","email":"","orcid":"","institution":"Zhejiang A\u0026F University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Pan","middleName":"","lastName":"Yang","suffix":""},{"id":303307168,"identity":"3f576725-e1c4-458c-95c7-4bbfb71b848c","order_by":6,"name":"Jiawei Ma","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyklEQVRIiWNgGAWjYBACxmYwZcPAwHwASLMRryUNqDqBSC1QcJgELcztzM+kbtSct+dv4zFg+FB2mIF/dgMhh7GZSeccu80scYzHgHHGucMMEncOENLCYHY7h+02G8P9HgNm3rbDDAYSCYS0sH+7nfPvHI880Bbmv8Rp4TG7ndt2QMIApIWRSC3lv3P7kg0Mj7EVHOw5l84jcYOAFsP+45uNc77Z2csdY9744EeZtRz/DEJaGpA4B4CYB796IJAnqGIUjIJRMApGAQCxUT3XPs3KhAAAAABJRU5ErkJggg==","orcid":"","institution":"Zhejiang A\u0026F University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Jiawei","middleName":"","lastName":"Ma","suffix":""},{"id":303307171,"identity":"290d930c-c15e-47a9-8967-ab237ad83635","order_by":7,"name":"Zhengqian Ye","email":"","orcid":"","institution":"Zhejiang A\u0026F University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhengqian","middleName":"","lastName":"Ye","suffix":""},{"id":303307172,"identity":"ec226ba8-c2f9-46e3-9ec6-425b28a68743","order_by":8,"name":"Dan Liu","email":"","orcid":"","institution":"Zhejiang A\u0026F University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Dan","middleName":"","lastName":"Liu","suffix":""}],"badges":[],"createdAt":"2024-05-06 02:41:35","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4373613/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4373613/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":56782824,"identity":"5cabb5ea-b38b-4dba-8a08-555d3ed3db22","added_by":"auto","created_at":"2024-05-20 11:59:00","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":743609,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of different treatments on root dry weight and plant height of tea seedlings\u003c/p\u003e\n\u003cp\u003eNote: Different lowercase letters indicate significant differences between treatments (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05), the same below.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4373613/v1/4afb9c7b443d71e91b1d4565.png"},{"id":56782826,"identity":"d42eb808-8720-4842-9b38-e018a3b78a94","added_by":"auto","created_at":"2024-05-20 11:59:00","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":625652,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of different treatments on soil pH and organic matter in tea garden.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4373613/v1/f5df3042776bdee036a55251.png"},{"id":56783496,"identity":"69eca4b1-b071-4e3c-b804-2ea99732a97f","added_by":"auto","created_at":"2024-05-20 12:07:00","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":618709,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of different treatments on exchangeable calcium and magnesium in tea garden soil\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4373613/v1/b59223867fae041adc08320d.png"},{"id":56782823,"identity":"22771dff-a982-4c02-88c0-5bca34963aa5","added_by":"auto","created_at":"2024-05-20 11:59:00","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":379850,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of different treatments on SPAD value of fresh tea leaves\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4373613/v1/8f70f408e4ea2948b85cb7e6.png"},{"id":62837741,"identity":"d52f2cd6-988b-4fa9-abbf-2c3be14d1873","added_by":"auto","created_at":"2024-08-20 05:45:14","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4979961,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4373613/v1/ed6089cc-e5b4-48af-9e85-4daf02d89ff6.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Magnesium-modified biochar improves tea quality and growth of tea plant by improving soil properties and promoting nutrient uptake","fulltext":[{"header":"Introduction","content":"\u003cp\u003eTea plant is one of the important cash crops, and the area planted of china ranks first in the world\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. According to data from the National Bureau of Statistics\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e, in 2020 China's tea plantation area of 3,216,700 hectares accounted for 62.1% of global tea plantation area and tea production was 2,931,800 tons and represented 46.77% of global tea production. This represented increases of 66.51 and 100.46% than that of 10 years ago\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSoil Mg availability is thus related to tea plant growth and tea quality\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. In addition, the optimum pH range for tea plants is 4.5 to 6.0, and the growth of tea plant was inhibited when pH\u0026lt;4.0\u003csup\u003e5\u003c/sup\u003e. Soil acidification can also be detrimental by increasing exchangeable aluminum (Al\u003csup\u003e3+\u003c/sup\u003e) from the soil\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Accumulation of Al in tea garden soils can also interchange with Mg soil colloids resulting in Mg leaching losses that adversely affects the tea plant growth\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e and limits tea yields and quality\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. In addition, soil acidification leads to changes in soil microbial communities and reduces the decomposition rates of soil organic matter and adversely alters soil ecosystem health\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSoil acidification in tea plantations has been increasing due to a large number of high-intensity anthropogenic activities and an estimated 52% of tea plantation soils possess pH values\u0026thinsp;\u0026lt;\u0026thinsp;4.5\u003csup\u003e9\u003c/sup\u003e. This has been the result of the acidification effects of chemical fertilizers (especially nitrogen fertilizers) put into the tea plantation soils and increases Mg leaching\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. Soil Mg content was lower than 50 mg kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e in 73% tea gardens in China\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. These red soil hilly areas in southern China cause strong leaching due to the warm and humid rainy climate and when coupled with the large amount of nitrogen fertilizers applied, leads to soil acidification, soluble Mg loss and a decline in the effective Mg content and reservoir\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Therefore, there is an urgent need to explore suitable amendments to alleviate and repair acidified tea garden soils and to increase soil Mg content to meet the Mg nutritional requirements of tea plants.\u003c/p\u003e \u003cp\u003eBiochar is a novel soil conditioner and possesses unique physicochemical properties that promote soil structure and overall health. Biochar was found to be superior in enhancing tea garden soil buffering capacity and long-term applications increased the soil pH of tea garden soils\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. The application of biochar in acidic red loam tea garden soil also effectively improved soil buffering and microbial activity and these were conducive to soil nutrient transformations\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eConventional biochar has certain limitations due to its own properties and the by-products produced during the pyrolysis process. These included a smaller specific surface area and a limited number of surface functional group species\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Physical, chemical and biological methods have been used to modify traditional biochar to improve biochar efficiency. These treatments increased the specific surface area resulting in an increased number of surface adsorption sites and further improved its adsorption capacity for pollutants such as heavy metals and reactive aluminum\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. In addition, biochar modified by impregnation with metal salt solutions resulted in metal oxide attachment to its surface that could effectively increase the content of soil salt-based ions after application and further increase the soil's ability to retain and supply fertilizer\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. For instance, montmorillonite could be modified using Fe and Al and sludge-based biochar with Mg salt impregnation. These treatments increased the efficiency of adsorptive properties and enhanced catalytic activity\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThere are few studies on the application of magnesium-modified biochar for tea plantations. Therefore, we investigates the effect of magnesium-modified biochar on soil nutrient content and tea quality in tea plantations, and introduces magnesium ions needed for the growth and development of tea plants at the same time of soil improvement, which provides more choices of materials for acidified soil improvement and improves tea quality.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eEffect on root dry weight and plant height of tea plants\u003c/h2\u003e \u003cp\u003eThe results in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e showed that both conventional magnesium fertilizer and biochar treatments could increase the root dry weight and plant height of tea plant to some extent compared with CK treatment. The root dry weight of tea plant in BC and BCY treatments was significantly increased by 16.67% and 57.41%, respectively, compared with the CK treatment (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and the root dry weight of tea plant in FC treatment was increased by 5% compared with the CK treatment, but the difference was not significant (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05).The root dry weight of tea plant in FC, BC and BCY treatments was significantly increased by 4.11%, 8.22% and 10.49%, respectively, compared with the CK treatment and BCY treatments significantly increased tea plant plant height by 4.11%, 8.22% and 10.49%, respectively, compared with CK treatment (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). It can be seen that acidified tea garden species adding conventional magnesium fertilizer and biochar can promote tea plant root system and tea plant growth to a certain extent, in which the application of biochar on the tea plant root growth is significantly better than the conventional application of magnesium fertilizer, and the application of magnesium-modified biochar on the root system of the tea plant and the growth of the tea plant are better than the application of common biochar to promote the effect of the tea plant root system and the growth of the tea plant..\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eEffect on soil pH and organic matter in tea plantations\u003c/h2\u003e \u003cp\u003eThe effects of different treatments on soil pH and organic matter in tea plantations are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, BC and BCY treatments to tea plantation soils both increased soil pH and organic matter content, and the soil pH of conventional magnesium fertilizer treatment was lower than that of the control; the highest soil pH was found in the BCY treatment, and the soil pH of BC and BCY treatments was significantly increased by 0.3 and 0.42 units, respectively(\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) ); while FC treatment soil pH decreased by 0.02 units (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The effect of different treatments on the enhancement of soil organic matter content in tea plantations was BC\u0026thinsp;\u0026gt;\u0026thinsp;BCY\u0026thinsp;\u0026gt;\u0026thinsp;FC, and the soil organic matter content of tea plantations in BC and BCY treatments was significantly higher than that in CK treatment by 28.04 and 22.93 g\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Thus, the application of biochar and magnesium-modified biochar in tea garden soil could significantly increase soil pH and organic matter content, thus slowing down the acidification of tea garden soil and providing a long-term source of organic carbon for the soil, in which the effect of magnesium-modified biochar in increasing soil pH was better than that of ordinary biochar.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e \u003ch2\u003eEffect on soil nutrient content in tea plantations\u003c/h2\u003e \u003cp\u003eAdding BC and BCY treatments could improve the nutrient content of tea garden soil to a certain extent, and the alkaline nitrogen content of tea garden soil in BC and BCY treatments was increased by 3.04 mg\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e and 1.27 mg\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e compared with CK treatment(Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e); FC、BC and BCY treatments could all increase the effective phosphorus and quick-acting potassium content of tea garden soils, and the effective phosphorus content of FC, BC and BCY treated soils was significantly higher than that of the CK treatment by 6.19 mg\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, 12.60 mg\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e and 23.06 mg\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, respectively (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05);Soil quick potassium content was increased by 1.87 mg\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e in FC treatment and significantly increased by 14.39 mg\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e and 5.00 mg\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e in BC and BCY treatments, respectively, over CK treatment (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05)..\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eEffect on soil nutrient content in tea plantations\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTreatment\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eSoil nutrient content in tea garden\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN(mg/kg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP(mg/kg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eK(mg/kg)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e45.14\u0026thinsp;\u0026plusmn;\u0026thinsp;1.67a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e27.31\u0026thinsp;\u0026plusmn;\u0026thinsp;1.28d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e35.67\u0026thinsp;\u0026plusmn;\u0026thinsp;0.84c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e34.09\u0026thinsp;\u0026plusmn;\u0026thinsp;4.71b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33.50\u0026thinsp;\u0026plusmn;\u0026thinsp;1.05c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e37.54\u0026thinsp;\u0026plusmn;\u0026thinsp;1.84b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48.18\u0026thinsp;\u0026plusmn;\u0026thinsp;1.40a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e39.91\u0026thinsp;\u0026plusmn;\u0026thinsp;2.22b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e50.06\u0026thinsp;\u0026plusmn;\u0026thinsp;3.19a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBCY\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e46.41\u0026thinsp;\u0026plusmn;\u0026thinsp;2.79a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50.37\u0026thinsp;\u0026plusmn;\u0026thinsp;1.05a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e40.67\u0026thinsp;\u0026plusmn;\u0026thinsp;0.88b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eNote : Different lowercase letters in the same column indicate significant differences between treatments ( \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05 ), the same below.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e\n\u003ch3\u003eEffect of different treatments on exchangeable calcium and magnesium in tea garden soil\u003c/h3\u003e\n\u003cp\u003eAs can be seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e: the soil exchangeable calcium content with added biochar and magnesium-modified biochar treatments was significantly higher than CK and FC treatments, and the soil exchangeable calcium content with BC and BCY treatments was significantly increased by 16.96% and 21.74% and 16.45% and 21.21%, respectively (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The addition of magnesium-modified biochar to the tea garden soil could significantly increase the soil exchangeable magnesium content, and the BCY treatment had the highest soil exchangeable magnesium content of 4.71 cmol\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e; the soil exchangeable magnesium content of the BCY treatment was significantly increased by 3.09 cmol\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e and 3.87 cmol\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e compared with that of the CK treatment and the BC treatment (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). It can be seen that both added biochar and magnesium-modified biochar can improve the soil exchangeable calcium and magnesium content of acidified tea plantations to a certain extent, while the effect of magnesium-modified biochar treatment in enhancing soil exchangeable magnesium content was more obvious..\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eEffect of different treatments on photosynthesis of tea plant\u003c/h2\u003e \u003cp\u003eThe strength of photosynthesis of tea plant was indicated by the relative chlorophyll content (SPAD value) of tea fresh leaves, and the changes of SPAD value of tea fresh leaves in different treatments were shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. As can be seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the size of SPAD value was BCY\u0026gt;BC\u0026gt;FC\u0026gt;CK, and conventional magnesium fertilizer and added biochar and magnesium-modified biochar treatments could significantly increase the SPAD value of tea plant fresh leaves, in which the SPAD value of tea plant fresh leaves of BC and BCY treatments were significantly higher than that of CK and FC treatments by 17.6, 37.6, and 6.4, 26.4, respectively (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). It can be seen that conventional magnesium fertilizer and biochar addition can significantly increase the SPAD value of tea plant fresh leaves, promote the photosynthesis of tea plants in acidified tea plantations, and facilitate the accumulation of carbohydrates in tea leaves, among which the magnesium-modified biochar treatment has a better effect.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eEffect of different treatments on nutrient accumulation in tea leaves\u003c/h2\u003e \u003cp\u003eAs shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, FC、BC and BCY treatments could promote the uptake of N, P, K, Ca and Mg nutrients in tea leaves; the increase in the accumulation of N in tea leaves of FC, BC and BCY treatments ranged from 2.49 to 8.74 g\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e compared with CK, in which the accumulation of N in tea leaves of BC and BCY treatments increased significantly by 11.33% and 18.43% ( \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05); the accumulation of P in tea leaves of FC, BC and BCY treatments increased in the range of 0.19\u0026ndash;1.44 g\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, of which the accumulation of P in tea leaves of BCY treatment increased significantly by 16.61% (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05); Compared with CK, the increases of K and Ca accumulation in tea leaves of FC, BC and BCY treatments were 0.30\u0026ndash;3.27 g\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e and 0.26\u0026ndash;0.84 g\u0026middot;kg\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, and the K and Ca accumulation in tea leaves was highest in BCY treatment, and the differences of Ca accumulation in tea leaves among treatments did not reach the significant level; Magnesium-modified biochar treatment was able to significantly increase tea Mg accumulation compared with other treatments, and tea Mg accumulation increased significantly by 57.09% in BCY treatment compared with CK. It can be seen that conventional magnesium fertilizer, added biochar and magnesium-modified biochar can all promote the uptake of N, P, K, Ca and Mg nutrients in tea leaves, thus promoting the growth of tea plants, of which the comprehensive results of magnesium-modified biochar treatment had the best effect.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDifference analysis of nutrient accumulation in tea\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTreatment\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c6\" namest=\"c2\"\u003e \u003cp\u003eNutrient accumulation of tea(g/kg)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eK\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCa\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMg\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e43.62\u0026thinsp;\u0026plusmn;\u0026thinsp;2.08d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.47c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.45\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.77\u0026thinsp;\u0026plusmn;\u0026thinsp;0.45a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e46.11\u0026thinsp;\u0026plusmn;\u0026thinsp;1.01cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.20bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.83a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.69\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48.59\u0026thinsp;\u0026plusmn;\u0026thinsp;1.72bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.26\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.22\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBCY\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e51.66\u0026thinsp;\u0026plusmn;\u0026thinsp;1.58ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.44\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.72\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.32a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003eEffect of different treatments on the main quality components of tea leaves\u003c/h2\u003e \u003cp\u003eAs shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, FC、BC and BCY treatments could affect the tea quality, and the tea polyphenol content of tea leaves showed BC\u0026gt;BCY\u0026gt;FC, of which the tea polyphenol content of tea leaves in BC treatment was the highest (16.53%), which was significantly higher than that of CK and FC treatments (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05); Compared with the CK treatment, the caffeine and amino acid contents of tea leaves of BCY, BC and FC treatments were significantly increased by 39.04%, 30.93%, 14.71% and, 15.81%, 15.20% and 12.16%, respectively (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The variation of water leachate content of tea leaves in different treatments ranged from 37\u0026ndash;48%. Conventional magnesium fertilizer, added biochar and magnesium-modified biochar could increase the water leachate content of tea leaves to different degrees, and added magnesium-modified biochar BCY treatment increased the water leachate significantly by 25.16% compared with the CK treatment (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05).The phenol-ammonia ratio of tea leaves in different treatments was CK\u0026gt;BC\u0026gt;BCY\u0026gt;FC, and the lowest phenol-ammonia ratio of tea leaves in BCY treatment with magnesium-modified biochar was significantly lower than that in CK treatment. In conclusion, adding BC and BCY treatments can improve the content of various quality components of tea, in which the effect of improving the quality of tea is more obvious with the addition of magnesium-modified biochar BCY treatment.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDifference analysis of main quality components content of tea\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTreatment\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c6\" namest=\"c2\"\u003e \u003cp\u003eMain Quality Components of Tea\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003etea polyphenol(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ecaffeine(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eamino acid(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ewater extracts(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ephenol ammonia\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e37.59\u0026thinsp;\u0026plusmn;\u0026thinsp;1.26b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.47\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15.53\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.82\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.69\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e39.22\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.21\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16.53\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.36\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.79\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e43.66\u0026thinsp;\u0026plusmn;\u0026thinsp;1.45b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.36\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBCY\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.61a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.63\u0026thinsp;\u0026plusmn;\u0026thinsp;0.16aa\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.81\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e47.05\u0026thinsp;\u0026plusmn;\u0026thinsp;1.65a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eEffect of magnesium-modified biochar on the improvement of acidified tea plantation soil\u003c/h2\u003e \u003cp\u003eThe optimal pH range for tea plant growth is 4.5 to 6.0, and our study showed that the application of biochar could increase the pH of acidified tea plantation soil. Biochar is alkaline and contains alkaline groups, which can neutralize the H\u003csup\u003e+\u003c/sup\u003e contained in the soil solution after being applied to the soil, which is consistent with the results of Xie and Wu\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Biochar is a carbon-containing material with a porous structure and stable, and the pH of the tea garden soil decreased significantly after a long period of time in the potting experiment, which may be related to the fact that the nitrogen in the organic matter was converted by the microorganisms into ammonia nitrogen and ammonium root ions (NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e) and further nitrified to release H\u003csup\u003e+\u0026thinsp;23\u003c/sup\u003e. We also found that BCY treatment was more effective than BC treatment in increasing the pH of acidified tea plantation soil, which was attributed to the fact that BCY treatment was introduced with compounds (magnesium oxide, etc.) in the process of preparation, which were able to form more chemical bonds with the biochar indicating that the magnesium-modified biochar had a higher specific surface area, contained soluble alkaline matrix substances\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e, which could adsorb the H\u003csup\u003e+\u003c/sup\u003e in the soil solution and increase soil salt-based ion content\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eOrganic matter is an important component of soil, which contains various nutrients needed for plant growth and plays a very important role in soil fertility and sustainable agricultural development\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. Some studies have shown that the direct addition of crop residues\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e, organic fertilizers, and other agricultural and forestry waste organic matter to the soil\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. Biochar can increase soil organic carbon content\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. In this experiment, the biochar applied to the soil of acidified tea plantation, which itself belongs to the biomass material with high carbon content, was directly applied to the soil of tea plantation which is equivalent to the direct input of a large amount of organic carbon into the soil, which is conducive to the effect of increasing the accumulation of soil organic matter. This is similar to the results of many studies, such as Li\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e, which showed that both rice and corn stover charcoal could improve the acidity of red loamy rice soil, and increase soil organic carbon and soil nutrient content. Xu\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003efound that soil application of biochar could increase the total soil carbon stock of moso bamboo forests, thus promoting the carbon sequestration capacity of moso bamboo forest ecosystems through long-term field experiments in moso bamboo forests. As a carbon-rich biomass material, biochar plays a significant role in sequestering carbon and increasing sinks\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSoil nutrient content is a direct source of nutrient uptake for tea plant growth, and some studies have shown that the application of biochar can significantly increase soil nutrient content\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. This study showed that BC and BCY treatment increased the alkaline dissolved nitrogen content of tea garden soil compared with CK treatment, indicating that soil addition of biochar may promote the mineralization of soil organic nitrogen, thus releasing inorganic nitrogen\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. In addition, it has been found that soil addition of biochar reduces leaching and volatilization loss of soil nitrogen, thus increasing soil nitrogen content\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. In this study, it was found that both BC and BCY treatment could increase the effective phosphorus content of tea garden soils, which was attributed to the fact that, on the one hand, the solubility of PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3-\u003c/sup\u003e was low in the more acidic soil conditions, and the biochar increased the soil pH thereby promoting the dissolution of PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3-\u003c/sup\u003e in the soil\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e; on the other hand, the biochar itself carried phosphorus, which was released by adding it to the soil thereby increasing the effective phosphorus content of the soil\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. Changes in soil quick potash in tea plantations may be related to changes in soil pH in tea plantations\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e, and the results of this study showed that all biochar treatments increased soil quick potash content, the reason for this is because biochar itself contains a certain amount of potassium, so that the application of all biochar increased soil quick potash content in tea plantations\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSoil exchangeable calcium and magnesium is an important component of soil salt-based substances and is a very important chemical property of soil\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e. In this study, both BC and BCY treatment could increase the soil exchangeable calcium and magnesium content of acidified tea plantations to a certain extent, which could be attributed to the fact that biochar contains a large number of salt-based ions, which were added to the soil to increase the soil exchangeable calcium and magnesium content on the one hand\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e, and on the other hand, it might be due to the fact that the soil acid solubilization promotes certain soil minerals to release salt-based ions\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. This study also found that the addition of BCY treatment to the soil significantly increased the soil exchangeable magnesium content\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e, suggesting that the magnesium element loaded on the biochar was converted into exchangeable Mg\u003csup\u003e2+\u003c/sup\u003e in the soil, similar to the results of other studies on the amelioration of soil acidification\u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e. Dai\u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003efound that modified biochar prepared by mixing raw materials could increase the pH, salinity ions and pH buffering properties of the soil, as well as reduce the exchangeable aluminum concentration of the soil. Qin\u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003eused magnesium-modified biochar for indoor soil simulation tests and found that magnesium-modified biochar prepared at different pyrolysis temperatures not only had larger porosity but also had more -OH and -COOH functional groups compared with unmodified biochar, which could reduce the soil acidity and at the same time, effectively improve the soil fertility, soil exchangeable calcium and magnesium content.\u003c/p\u003e \u003cp\u003eFor tea garden soils with high acidification and low organic matter content, using the qualities of magnesium-modified biochar for amendment can significantly reduce soil acidity\u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003eand increase the organic matter content of acidified tea garden soils\u003csup\u003e\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e,\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003ewhile also increasing soil nutrient content \u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e, so that the tea garden soils develop in the direction of being more conducive to the growth of tea plants, and improve the yield of tea gardens and the quality of tea leaves\u003csup\u003e\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e,\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eEffect of magnesium-modified biochar on the growth of tea seedlings and tea quality\u003c/h2\u003e \u003cp\u003eThe addition of biochar improves soil acidity, increases soil organic matter content, and improves soil nutrient content so as to meet the nutrient demand of tea plant during its reproductive period\u003csup\u003e\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e, and significantly enhances the absorption and accumulation of nitrogen, phosphorus, potassium, and calcium and magnesium nutrients in tea. Plant root system is an important organ for absorbing soil nutrients, and its growth and development will directly affect the absorption of soil nutrients by plants. In this experimental study, it was found that biochar in acidified tea garden soil could promote the growth of tea plant roots, which was due to the fact that on the one hand, biochar was able to improve soil acidity, reduce soil bulk weight, and increase soil aeration pore space\u003csup\u003e\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e\u003c/sup\u003e; on the other hand, it was able to improve soil pH, salinity ions, and alleviate the toxic effect of aluminum in acidified soils, which in turn promoted the growth of tea plant roots\u003csup\u003e\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e\u003c/sup\u003e. This study also found that BCY treatment promoted the root growth of tea seedlings significantly better than BC treatment, which is because magnesium-modified biochar can increase the magnesium necessary for the growth of tea plants while alleviating aluminum toxicity, thus promoting the root growth and development of tea plants.\u003c/p\u003e \u003cp\u003eIn this study, BC and BCY treatment could promote the uptake of nitrogen, phosphorus, potassium, and calcium and magnesium nutrients in tea leaves to different degrees, and tea plant is an ammonium-loving plant, and the addition of biochar significantly increased the supply of alkaline dissolved nitrogen (ammonium nitrogen) in the soil, which promoted the uptake of nitrogen by tea plant\u003csup\u003e\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u003c/sup\u003e; Magnesium is an important component of tea plant chlorophyll and affects tea plant leaf photosynthesis\u003csup\u003e\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e\u003c/sup\u003e, due to the addition of biochar increased the effective magnesium content of acidified tea garden soil, promoting the absorption of magnesium by tea plants and the synthesis of tea chlorophyll, thus enhancing tea photosynthesis. In this study, magnesium-modified biochar, because of its large magnesium loading, was added to the soil to significantly increase the absorption of magnesium by tea plants, significantly increase the SPAD value of the fresh leaves of tea plants in acidified tea gardens, and contribute to the promotion of photosynthesis and the synthesis of carbohydrates in tea leaves.\u003c/p\u003e \u003cp\u003eTea garden soil nutrient content directly affects the growth and development of tea plants, which in turn affects the quality of tea, tea quality is generally determined by the tea polyphenols, caffeine, amino acids, water leachate and phenol-ammonia ratio and other indicators\u003csup\u003e\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e\u003c/sup\u003e. Tea polyphenol consists of various phenolic compounds, mainly affects the aroma and taste of tea, tea unique tea flavor and sweetness from tea polyphenol, tea polyphenol content is appropriate at about 20%, too high will lead to tea bitterness and astringency directly affect the quality of tea\u003csup\u003e\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e\u003c/sup\u003e. In this study, the tea polyphenol content of all treatments ranged from 15.50\u0026ndash;17.00%, and the addition of biochar was able to increase the tea polyphenol content, of which the tea polyphenol content of BCY treatment was the highest and significantly higher than that of the CK and FC treatments (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). This is due to the fact that tea polyphenol content is closely related to the nutrients (nitrogen, phosphorus and potassium) in tea leaves, and an increase in the accumulation of nitrogen, phosphorus and potassium nutrients increases the tea polyphenols synthesized by the tea plant\u003csup\u003e\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e\u003c/sup\u003e. The study of Jiang\u003csup\u003e\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e\u003c/sup\u003efound that the application of biogas and biochar can increase the amino acid content of tea and help to improve the quality of tea, which is the same as the results of this study. Caffeine and amino acids are important substances for the freshness of tea broth, and water leachate is important for the strong flavor of tea broth\u003csup\u003e\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e\u003c/sup\u003e. The results of this study showed that BC and BCY treatment could increase the content of caffeine, amino acids and water leachate in tea, and the magnesium-modified biochar enhancement effect was significantly better than that of unmodified biochar, which could make the tea broth fresh and refreshing, with a high and long aroma, and better quality.\u003c/p\u003e \u003c/div\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eSoil Information\u003c/h2\u003e \u003cp\u003eThe test soils were taken in June 2022 from a tea plantation base in Lin'an District, Hangzhou City, Zhejiang Province, which was planted with tea plants for 10 years. The area has a subtropical monsoon climate with an annual average temperature of 15.9℃, an average annual precipitation of 1420 mm and a red loam soil texture. Soil samples were taken according to the \"S\" type multi-point mixed collection at 0\u0026thinsp;~\u0026thinsp;20 cm depths, air-dried followed by stone and dead leave removal. The soil was then ground and passed through a 2 mm sieve and used for basic chemistry testing (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBasic physical and chemical properties of tea plantation soil used in these experiments\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eOrganic matter (g kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAvailable N (mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1)\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAvailable P (mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eAvailable K (mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eExchangeable Mg (cmol kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ered loam soil\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e4.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e12.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e32.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e27.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e67.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.78\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eBiochar preparation\u003c/h2\u003e \u003cp\u003eDiscarded tea plant branches were collected, rinsed 2\u0026ndash;3 times with distilled water then dried at ambient temperature. The branches were then crushed and pyrolyzed under anaerobic conditions at 500\u0026deg;C for 2h in a muffle furnace. This biochar was designated BC. Modified biochars were prepared using tea plant twig powder was homogeneously mixed with Mg(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e (designated \u0026lsquo;Y\u0026rsquo; treatment)solutions at 1 g:10 mL (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The mixtures were oscillated at frequency of 220 rpm at 30\u0026deg;C for 1 h, sealed and impregnated for 23 h, filtered, dried at 105\u0026deg;C, and placed in a muffle furnace and pyrolyzed under anaerobic conditions at 500\u0026deg;C for 2 h. The furnace was then allowed to cool to room temperature and the obtained product was ground and passed through a 100-mesh sieve to produce Mg-modified biomass charcoal (MgBC).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBiochar-modified salt solutions\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerial number\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eModifier\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eConcentration (M)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBCY\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMg(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eExperimental design\u003c/h2\u003e \u003cp\u003eFour treatments were set up: control (no biochar added, CK), conventional magnesium fertilizer treatment (FC), tea plant branch biochar treatment (BC), and, magnesium acetate modified biochar (BCY), with three replications for each treatment. High-quality tea seedlings with good growth and basic uniform plant size were selected, and the seedlings were taken to ensure that the root system was intact and able to survive. Pour 5 kg of soil into the potting bowl, mix the biomass charcoal and soil (2%) thoroughly, fertilizer as a basal fertilizer applied at once, each potting bowl transplanted 4\u0026ndash;6 tea seedlings, the first watering watered thoroughly, field water holding capacity to maintain 70%. Cultivation of the early need to be based on the survival of tea seedlings, there is a need to replenish seedlings, the 30th d of the test each pot of 1.25 g urea, usually potted tea plants in accordance with the daily management of the tea garden field, the experimental management measures of the treatment is the same.\u003c/p\u003e \u003cp\u003eThe entire treatment process for a total of 3 months, the collection of tea plant samples, tea seedlings with the root system complete take out and bring back to the laboratory, with deionized water to quickly wash the root system attached to the soil after the tea roots and stems and leaves are separated, the quality of tea sampling standards for the first bud and two leaves of the tea fresh leaves, packed into envelopes and marking, put into the oven at 105 ℃ to kill the green for 1h in 50 ℃ drying to constant weight, the plant samples placed in a pulverizer, and then dried to constant weight. The plant samples were ground in a pulverizer and sieved, and stored in plastic self-sealing bags for the determination of tea-related indexes. Soil samples were taken by broken ring sampling, soil samples were dried naturally, ground and sieved, and then stored for the determination of related indexes.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eIndicators and methods\u003c/h2\u003e \u003cp\u003eThe analytical methods of soil samples were referred to Soil Agrochemical Analysis (Third Edition)\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e: soil pH was determined by potentiometric method with soil-water ratio of 1:2.5; soil organic matter was determined by volumetric method with externally heated potassium dichromate; effective soil phosphorus was determined by hydrochloric acid-ammonium fluoride dissolution-molybdenum antimony antimony colorimetry; quick-acting potassium of the soil was determined by ammonium acetate leaching and flame photometric method; alkaline nitrogen of the soil was measured by alkaline dissolution diffusion method Soil cation exchange capacity (CEC) was determined by 1 mol/L ammonium acetate exchange method; soil exchangeable salty ions were extracted by 1 mol/L ammonium acetate solution, and Ca and Mg in the extract were determined by atomic absorption spectrophotometry.\u003c/p\u003e \u003cp\u003eMeasurement of tea-related indexes: SPAD value of tea leaves in each treatment was determined by chlorophyll meter; total nitrogen of tea leaves was determined by carbon and nitrogen analyzer method; total phosphorus was determined by H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e digestion-molybdenum antimony antimony colorimetry method; total potassium was determined by H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e digestion-flame photometer method; total calcium and magnesium were determined by H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e cooking-atomic absorption spectrophotometry was used for total potassium; total calcium and magnesium were used for total calcium and magnesium. Tea polyphenols were determined by the colorimetric method of forintol (GB /T 8313\u0026thinsp;\u0026minus;\u0026thinsp;2018); caffeine was determined by ultraviolet spectrophotometry (GB /T 8312\u0026thinsp;\u0026minus;\u0026thinsp;2013); free amino acids were determined by the colorimetric method of ninhydrin (GB /T 8314\u0026thinsp;\u0026minus;\u0026thinsp;2013); water extracts were determined by the boiling water extraction method (GB /T 8314\u0026thinsp;\u0026minus;\u0026thinsp;2013); water extracts were determined by the flame photometric method of HSO4H2O2 digestion and atomic absorption spectrophotometry. leachate was determined by boiling water extraction-weight method (GB /T 8305\u0026thinsp;\u0026minus;\u0026thinsp;2013).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analyses\u003c/h2\u003e \u003cp\u003eOne-way analysis of variance (ANOVA) was performed using IBM SPSS Statistics 23 software. Duncan\u0026rsquo;s method was used to make multiple comparisons of the experimental data. The significance level of the difference was \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05 using Origin 2021. The experimental data were expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003eResearch involving plants statement\u003c/h2\u003e \u003cp\u003e Experimental research and feld studies on plants (either cultivated or wild), including the collection of plant material, comply with relevant institutional, national, and international guidelines and legislation.\u003c/p\u003e \u003cp\u003eTea trees purchased by Zhejiang A\u0026amp;F University, Plant samples are stored in the School of Environment and Resources, Zhejiang A\u0026amp;F University\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eOur study revealed the effects of magnesium-modified biochar on soil nutrient content and tea quality in acidified tea gardens. Biochar (both ordinary Biochar, magnesium-modified biochar) could improve soil pH and soil organic matter and our study showed that magnesium-modified biochar improved the quality of tea significantly via enhancing the pH, organic matter and nutrient content of soil, increasing the uptake of nitrogen, phosphorus, potassium, calcium and magnesium in the tea plant, and ascending photosynthesis, The best results were obtained with BCY treatment.\u003c/p\u003e \u003cp\u003eThis study plays a guiding role for the improvement and nutrient supplementation of acidified soil in tea plantations and promotes the healthy development of tea plantation soil.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was financed by the National Natural Science Foundation of China (32371543), Zhejiang High-level Talents Special Support Program (2020R52026), Research and Science Development Fund of Zhejiang A\u0026amp;F University(2023FR012).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInstitutional Review Board Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;No humans or animals were involved in this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInformed Consent Statement\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analysed during the current study are not publicly available due [For the sake of privacy of the individuals and team labs involved in the research] but are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflict of interest.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHu C. \u003cem\u003eet al.\u003c/em\u003e Current Status and Health Risk Assessment of Heavy Metals Contamination in Tea across China[J]. Toxics, 2023, 11(8): 662.\u003c/li\u003e\n\u003cli\u003eYan P. \u003cem\u003eet al\u003c/em\u003e. Soil acidification in Chinese tea plantations[J]. Science of The Total Environment, 2020, 715: 136963. \u003c/li\u003e\n\u003cli\u003eHou R. \u003cem\u003eet al\u003c/em\u003e. Sustainable Tea Garden Ecotourism Based on the Multifunctionality of Organic Agriculture Based on Artificial Intelligence Technology[J]. Mobile Information Systems, 2021, 2021: 8696490. \u003c/li\u003e\n\u003cli\u003eZhang Y. \u003cem\u003eet al\u003c/em\u003e. Effects of Magnesium on Transcriptome and Physicochemical Index of Tea Leaves[J]. Plants, 2023, 12(9): 1810. \u003c/li\u003e\n\u003cli\u003eTseng W-Y. \u003cem\u003eet al\u003c/em\u003e. Comprehensive Analysis Revealed the Specific Soil Properties and Foliar Elements Respond to the Quality Composition Levels of Tea (Camellia sinensis L.)[J]. Agronomy, 2022, 12(3): 670. \u003c/li\u003e\n\u003cli\u003ePan X-Y. \u003cem\u003eet al\u003c/em\u003e. Characteristics of crop straw-decayed products and their ameliorating effects on an acidic Ultisol[J]. Archives of Agronomy and Soil Science, 2021, 67(12): 1708-1721. \u003c/li\u003e\n\u003cli\u003eKunito T. \u003cem\u003eet al\u003c/em\u003e. Aluminum and acidity suppress microbial activity and biomass in acidic forest soils[J]. Soil Biology and Biochemistry, 2016, 97: 23-30. \u003c/li\u003e\n\u003cli\u003eJoris H A W. \u003cem\u003eet al\u003c/em\u003e. Effects of soil acidity and water stress on corn and soybean performance under a no-till system[J]. Plant and Soil, 2013, 365(1): 409-424. \u003c/li\u003e\n\u003cli\u003eYi X. \u003cem\u003eet al\u003c/em\u003e. Organic amendments improved soil quality and reduced ecological risks of heavy metals in a long-term tea plantation field trial on an Alfisol[J]. Science of The Total Environment, 2022, 838: 156017. \u003c/li\u003e\n\u003cli\u003eArafat Y. \u003cem\u003eet al\u003c/em\u003e. Long-Term Monoculture Negatively Regulates Fungal Community Composition and Abundance of Tea Orchards[J]. Agronomy, 2019, 9(8): 466. \u003c/li\u003e\n\u003cli\u003eWu X. Development of famous tea and application of magnesium fertilizer in tea plantations[J]. Tea Newsletter, 1994(3): 11-13. \u003c/li\u003e\n\u003cli\u003eZhu Y. \u003cem\u003eet al\u003c/em\u003e. Magnesium nutrition in red soil tea plantations in southern hills[J]. Tea Science, 2000(2): 95-100. \u003c/li\u003e\n\u003cli\u003eWang Y. \u003cem\u003eet al\u003c/em\u003e. Effects of biochar on soil properties and fungal community structure in acidified tea plantations[J]. Tea Science, 2021, 41(3): 419-429. \u003c/li\u003e\n\u003cli\u003eZheng H. \u003cem\u003eet al\u003c/em\u003e. Application of biochar to improve microbial characteristics and enzyme activities of acidic red soil tea plantation soils[J]. China Soil and Fertilizer, 2019(2): 68-74\u003c/li\u003e\n\u003cli\u003eBardestani R. \u003cem\u003eet al\u003c/em\u003e. Steam activation and mild air oxidation of vacuum pyrolysis biochar[J]. Biomass and Bioenergy, 2018, 108: 101-112. \u003c/li\u003e\n\u003cli\u003eAzargohar R. \u003cem\u003eet al\u003c/em\u003e. Steam and KOH activation of biochar: Experimental and modeling studies[J]. Microporous and Mesoporous Materials, 2008, 110(2): 413-421. \u003c/li\u003e\n\u003cli\u003eHuang C. Effects of common biochar and acid-modified biochar on soil water-salt distribution and spinach growth in mudflat area[D]. Yangzhou University, 2021. \u003c/li\u003e\n\u003cli\u003eLuo J. \u003cem\u003eet al\u003c/em\u003e. Characterization and catalytic performance of iron-aluminum column-supported acidified montmorillonite catalysts[J]. Industrial Catalysis, 2017, 25(1): 54-57.\u003c/li\u003e\n\u003cli\u003eYang Y. \u003cem\u003eet al\u003c/em\u003e. Removal of phosphorus and antibiotics from water by magnesium-modified sludge-based biochar[J]. China Environmental Science, 2022, 42(9): 4137-4144. \u003c/li\u003e\n\u003cli\u003eBao S. Soil agrochemical analysis [M]. Beijing, China Agricultural Press, 2000.\u003c/li\u003e\n\u003cli\u003eXie G. \u003cem\u003eet al\u003c/em\u003e. Effects of biochar amendment on degraded vegetable soil[J]. Journal of Southern Agriculture, 2014, 45 (1): 67-71\u003c/li\u003e\n\u003cli\u003eWu M. \u003cem\u003eet al\u003c/em\u003e. Effects of biochar on soil acidity and exchange capacity in rubber plantation[J]. China Agricultural Science and Technology Review, 2017,19 (3): 98-107.\u003c/li\u003e\n\u003cli\u003eWang N. \u003cem\u003eet al\u003c/em\u003e. Effects of three plant materials on the improvement of soil acidity in two tea gardens[J]. Soil, 2009,41 (5): 764-771.\u003c/li\u003e\n\u003cli\u003eYuan J-H. \u003cem\u003eet al\u003c/em\u003e. Effects of biochars generated from crop residues on chemical properties of acid soils from tropical and subtropical China[J]. Soil Research, 2012, 50(7): 570.\u003c/li\u003e\n\u003cli\u003eWang Y. \u003cem\u003eet al\u003c/em\u003e. Study on the improvement effect of biochar on soil acidity in strong acid tea garden[J]. China Agricultural Bulletin, 2018,34 (12): 108-111.\u003c/li\u003e\n\u003cli\u003eSun K. \u003cem\u003eet al\u003c/em\u003e. Effects of different organic materials application on phosphorus accumulation and transformation in vegetable field[J]. Environmental Science: 1-15.\u003c/li\u003e\n\u003cli\u003eLiang B. \u003cem\u003eet al\u003c/em\u003e. Black carbon affects the cycling of non-black carbon in soil[J]. Organic Geochemistry, 2010, 41(2): 206\u0026ndash;213.\u003c/li\u003e\n\u003cli\u003eKong J. \u003cem\u003eet al\u003c/em\u003e. Effects of straw addition on soil nitrogen dynamics under simulated freeze-thaw cycles[J]. Journal of Shenyang Normal University (Natural Science Edition), 2022, 40 (6): 527-534.\u003c/li\u003e\n\u003cli\u003eMeng Y. \u003cem\u003eet al\u003c/em\u003e. Integrated analysis of the effects of biochar application on soil aggregates and organic carbon in farmland [J]. Environmental Science: 1-13.\u003c/li\u003e\n\u003cli\u003eLi M. \u003cem\u003eet al\u003c/em\u003e. Effects of different straw biochars on nutrients and microbial community structure in red paddy soil [J]. China Agricultural Sciences, 2015,48 (7): 1361-1369.\u003c/li\u003e\n\u003cli\u003eXu L. \u003cem\u003eet al\u003c/em\u003e. Biochar application increased ecosystem carbon sequestration capacity in a Moso bamboo forest[J]. Forest Ecology and Management, 2020, 475: 118447.\u003c/li\u003e\n\u003cli\u003eJiang F. \u003cem\u003eet al\u003c/em\u003e. Effects of biochar on soil physical and chemical properties and tea yield in tea garden[J]. Acta Tea Sinica, 2015,56 (1): 16-22.\u003c/li\u003e\n\u003cli\u003eZhang S. \u003cem\u003eet al\u003c/em\u003e. Research progress on soil acidification in tea garden [J]. Tea, 2019, 45 (1): 17-23.\u003c/li\u003e\n\u003cli\u003eLehmann J. \u003cem\u003eet al\u003c/em\u003e. Biochar for environmental management: An introduction[J]. Biochar for Environmental Management: Science and Technology, 2009: 1\u0026ndash;12.\u003c/li\u003e\n\u003cli\u003eLehmann J. \u003cem\u003eet al\u003c/em\u003e. Nutrient availability and leaching in an archaeological Anthrosol and a Ferralsol of the Central Amazon basin: fertilizer, manure and charcoal amendments[J]. Plant and Soil, 2003, 249(2): 343\u0026ndash;357.\u003c/li\u003e\n\u003cli\u003eZhao X. \u003cem\u003eet al\u003c/em\u003e. Does Biochar Addition Influence the Change Points of Soil Phosphorus Leaching?[J]. Journal of Integrative Agriculture, 2014, 13: 499\u0026ndash;506.\u003c/li\u003e\n\u003cli\u003eZhai L. \u003cem\u003eet al\u003c/em\u003e. Short-term effects of maize residue biochar on phosphorus availability in two soils with different phosphorus sorption capacities[J]. Biology and Fertility of Soils, 2015, 51(1): 113\u0026ndash;122.\u003c/li\u003e\n\u003cli\u003eDeng X. \u003cem\u003eet al\u003c/em\u003e. pH and main nutrient characteristics of tobacco-planting soil in Xiangxi and their relationship[J].Soil, 2017,49 (1): 49-56.\u003c/li\u003e\n\u003cli\u003eLiu M.\u003cem\u003e et al\u003c/em\u003e. Effects of different biochars on soil nutrients and nitrogen use efficiency in aeolian sandy soil[J]. China Soil and Fertilizer, 2023 (5): 20-27.\u003c/li\u003e\n\u003cli\u003eYu Y. \u003cem\u003eet al\u003c/em\u003e. Distribution characteristics of soil cation exchange capacity and exchangeable base ions in Ehuangzhang Mountain Rainforest [J]. Soil Bulletin, 2022,53 (6): 1341-1349.\u003c/li\u003e\n\u003cli\u003eZheng M. \u003cem\u003eet al\u003c/em\u003e. Effects of biochar addition on soil base ion leaching under simulated acid rain[J]. Journal of Agricultural Environmental Sciences, 2021, 40 (1): 163-173.\u003c/li\u003e\n\u003cli\u003eLing D. \u003cem\u003eet al\u003c/em\u003e. Effects of simulated acid rain on the migration and release of base cations in latosol[J]. Soil Science, 2007 (3): 444-450.\u003c/li\u003e\n\u003cli\u003eKramer R W. \u003cem\u003eet al\u003c/em\u003e. Identification of Black Carbon Derived Structures in a Volcanic Ash Soil Humic Acid by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry[J]. Environmental Science \u0026amp; Technology, 2004, 38(12): 3387\u0026ndash;3395.\u003c/li\u003e\n\u003cli\u003eXue X. \u003cem\u003eet al\u003c/em\u003e. Effects of potassium and magnesium interaction on growth and nutrient uptake of rubber seedlings[J]. Acta Nutrienta Planta Sinica, 2020, 26 (10): 1870-1878.\u003c/li\u003e\n\u003cli\u003eDai Z. Research on the amelioration effect and biochemical mechanism of biochar on acidified soil [D]. Zhejiang University, 2017.\u003c/li\u003e\n\u003cli\u003eQin J. Preparation of magnesium-modified biochar with different pyrolysis temperatures and its effects on soil chemical properties and enzyme activities [D]. Guangxi University, 2021.\u003c/li\u003e\n\u003cli\u003eWang J. \u003cem\u003eet al\u003c/em\u003e. A soil management strategy for ameliorating soil acidification and reducing nitrification in tea plantations[J]. European Journal of Soil Biology, 2018, 88: 36\u0026ndash;40.\u003c/li\u003e\n\u003cli\u003eLe V S. \u003cem\u003eet al\u003c/em\u003e. How application of agricultural waste can enhance soil health in soils acidified by tea cultivation: a review[J]. Environmental Chemistry Letters, 2022, 20(1): 813\u0026ndash;839.\u003c/li\u003e\n\u003cli\u003eHu Y. \u003cem\u003eet al\u003c/em\u003e. Effects of biochar on CO2 and N2O emissions and microbial characteristics in tea garden soil[J]. Applied Ecology, 2015, 26 (7): 1954-1960.\u003c/li\u003e\n\u003cli\u003eXu L. Preparation and properties of magnesium-loaded biochar composites [D]. Hebei Normal University of Science and Technology, 2022.\u003c/li\u003e\n\u003cli\u003eSun Y. \u003cem\u003eet al\u003c/em\u003e. Effects of biochar on soil improvement and tea quality in tea garden[J]. China Soil and Fertilizer, 2017 (6): 9-14.\u003c/li\u003e\n\u003cli\u003eWu Z. \u003cem\u003eet al\u003c/em\u003e. Effects of biochar amendment on acidified tea garden soil[J]. Fujian Agricultural Journal, 2012, 27 (2): 167-172.\u003c/li\u003e\n\u003cli\u003eWang F. \u003cem\u003eet al\u003c/em\u003e. Effects of biochar combined with nitrogen fertilizer on tea plant growth and nitrogen use efficiency[J]. Tea Science, 2018, 38 (4): 331-341.\u003c/li\u003e\n\u003cli\u003eLi C. \u003cem\u003eet al\u003c/em\u003e. Effects of bulk density of subsoil on root growth and absorption activity of maize[J]. China Agricultural Sciences, 2005 (8): 1706-1711.\u003c/li\u003e\n\u003cli\u003eLiang X. \u003cem\u003eet al\u003c/em\u003e. Effects of biochar on root growth and physiological characteristics of quinoa in saline-alkali land[J]. Shandong Agricultural Sciences, 2020,52 (12): 24-29.\u003c/li\u003e\n\u003cli\u003eWang L. \u003cem\u003eet al\u003c/em\u003e. Effects of biochar and combined application with organic fertilizer on growth, nitrogen uptake and quality of Guixiang 22 tea plant[J]. Tropical Agricultural Sciences, 2018, 38 (6): 18-24 + 48.\u003c/li\u003e\n\u003cli\u003eHan W. \u003cem\u003eet al\u003c/em\u003e. Development of tea garden soil main nutrient obstacle factors and series of tea plant special fertilizer[J]. Tea Science, 2002 (1): 70-74 + 65.\u003c/li\u003e\n\u003cli\u003eLiu W. \u003cem\u003eet al\u003c/em\u003e. Compared the effects of different microbial fertilizers and chemical fertilizers on soil fertility and tea quality in tea gardens[J]. Soil and Fertilizer in China, 2023 (6): 78-86.\u003c/li\u003e\n\u003cli\u003eLi C. \u003cem\u003eet al\u003c/em\u003e. Effects of biochar-based fertilizer on soil nutrients and tea yield and quality in acidified tea garden[J]. Soil Bulletin, 2021, 52 (2): 387-397.\u003c/li\u003e\n\u003cli\u003eLi J. \u003cem\u003eet al\u003c/em\u003e. Effects of fertilization patterns on tea nutrient accumulation and soil fertility[J]. Jiangsu Agricultural Sciences, 2019, 47 (7): 170-174.\u003c/li\u003e\n\u003cli\u003eJiang Y. Effects of biogas slurry and biochar application on soil and tea quality in tea garden[D]. Zhejiang University of Science and Technology, 2023.\u003c/li\u003e\n\u003cli\u003eYi X. \u003cem\u003eet al\u003c/em\u003e. Analysis of main quality components of black tea from different producing areas[J]. Tea Newsletter, 2017, 44 (2): 30-33.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"biochar,magnesium-modified,acidified tea garden,soil nutrients,tea nutrient absorption,tea quality","lastPublishedDoi":"10.21203/rs.3.rs-4373613/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4373613/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSoil acidification affects the growth of tea plants and induces magnesium loss, which further reduces tea quality. In this study, magnesium-modified biochar was developed from discarded tea plant branches, via potting test to evaluate the effect on the red loam soil, and to study the quality of tea in acidified tea gardens. Four treatments were set up as control (no biochar added, CK), conventional magnesium fertilizer treatment (FC), tea plant branch biochar treatment (BC) and magnesium-modified biochar with acetic acid (BCY) respectively. Our results showed that soil pH was significantly increased by 0.3 and 0.42 units in BC and BCY treatments respectively, conventional magnesium fertilizer, biochar, and magnesium-modified biochar treatments could significantly increase soil organic matter, alkaline-dissolved nitrogen, effective phosphorus, quick-acting potassium, and exchanged calcium and magnesium content in acidified tea plantations. Compared with CK treatment, both conventional magnesium fertilizer treatment and biochar treatment could increase the root dry weight and tea plant height to some extent; the SPAD values of tea fresh leaves of BC and BCY treatments were significantly higher than those of CK and FC treatments by 17.6, 37.6 and 6.4, 26.4, respectively; and the increase in accumulation of nitrogen, phosphorus, potassium, calcium, and magnesium in tea leaves of FC, BC, and BCY treatments compared with that of CK was 2.49~8.04 g·kg\u003csup\u003e-1\u003c/sup\u003e, 0.19~0.49 g·kg\u003csup\u003e-1\u003c/sup\u003e, 0.30~3.27 g·kg\u003csup\u003e-1\u003c/sup\u003e, 0.26~0.50 g·kg\u003csup\u003e-1\u003c/sup\u003e, and 0.15~1.45 g·kg\u003csup\u003e-1\u003c/sup\u003e; and SPAD value, tea polyphenols, water leachate, caffeine, and amino acid contents of tea leaves in BC and BCY treatments were significantly higher than CK treatment (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). Our study showed that magnesium-modified biochar improved the quality of tea significantly via enhancing the pH, organic matter and nutrient content of soil, increasing the uptake of nitrogen, phosphorus, potassium, calcium and magnesium in the tea plant, and ascending photosynthesis, The best results were obtained with magnesium chloride modified biochar (BCL) treatment. This study plays a guiding role for the improvement and nutrient supplementation of acidified soil in tea plantations and promotes the healthy development of tea plantation soil..\u003c/p\u003e","manuscriptTitle":"Magnesium-modified biochar improves tea quality and growth of tea plant by improving soil properties and promoting nutrient uptake","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-20 11:58:55","doi":"10.21203/rs.3.rs-4373613/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"2b19480a-0d27-4b17-bb02-cf52f071207a","owner":[],"postedDate":"May 20th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":32014216,"name":"Earth and environmental sciences/Ecology/Agri ecology"},{"id":32014217,"name":"Biological sciences/Ecology/Agri ecology"}],"tags":[],"updatedAt":"2024-08-20T05:36:43+00:00","versionOfRecord":[],"versionCreatedAt":"2024-05-20 11:58:55","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4373613","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4373613","identity":"rs-4373613","version":["v1"]},"buildId":"omnImTCwR2MFx8CMYfrG7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}