Mechanism And Application Of Magnesium Fertilizer In Improve Soil Acidification In Tea Garden

Due to the use of a large number of chemical fertilizers,the tea garden soil is generally over acidified.The proportion of tea gardens with soil p H<4.5 is 52%,the soil fertility is reduced,and the area of tea gardens lacking magnesium is more than 57%,which affects the quality and yield of tea.It is found that exchangeable Mg²⁺in soil has a significant positive correlation with p H,but the action path and mechanism of exogenous magnesium fertilizer on soil exchangeable Mg²⁺and the improvement of tea garden soil acidification are not clear,which can not provide a scientific basis for magnesium fertilizer to improve tea garden soil acidification.Using acidified tea garden soil as experimental materials,the indoor soil culture experiment of applying magnesium fertilizer was carried out in Anxi Tea College of Fujian agriculture and Forestry University in Anxi County,Fujian Province from 2020 to 2022,and the field fertilization experiment was carried out in Xiandong village,Longmen Town,Anxi County,Fujian Province.Based on indoor soil culture experiment.,the field fertilization experiment was carried out to clarify the application effect of magnesium fertilizer in improving acidified tea garden.The results show that:1.The application of magnesium fertilizer can improve the acidification of tea garden soil,significantly increase the content of soil exchangeable Mg²⁺and reduce the content of soil exchangeable Al³⁺.The addition of 400mg·kg^-1 magnesium fertilizer had the most significant effect on improving the p H of the tested soil,and the p H was 339、p H4.00 and p H4.52 the p H of the tested soil increased by 6.3%～13.2%on average;The average of exchangeable Mg²⁺was increased by 67.25%～333%;Exchangeable Al³⁺decreased by 14.5%～41.4%on average,reaching a significant level.It shows that the application of magnesium fertilizer can significantly improve soil acidification.2.The application of magnesium fertilizer mainly improves the p H by increasing the direct effect path of soil exchangeable Mg²⁺and reducing the indirect effect path of exchangeable Al³⁺.For the three acidified tea garden soils,the direct effect path coefficient of exchangeable Mg²⁺on p H was the largest and reached a significant level,and the path coefficients were 0.5652,0.3417 and 0.3388respectively;The direct effect of exchangeable Mg²⁺on exchangeable Al³⁺reached a significant level,and the path coefficients were-0.6600,-0.4952,-0.8901 respectively;Exchangeable Mg²⁺had the highest effect on soil p H in tea garden,and the total effect coefficients were 0.8380,0.5322 and0.6935 respectively.It shows that in the process of applying magnesium fertilizer to improve acidified tea garden soil,exchangeable magnesium is the main acidification improvement factor,which mainly improves soil p H by increasing the direct effect path of exchangeable base and reducing the indirect effect path of exchangeable Al³⁺.3.The application of magnesium fertilizer also affects soil p H by greatly increasing the direct effect path of exchangeable Ca²⁺.For the three acidified tea garden soils,the direct effect path coefficient of exchangeable Ca²⁺on p H is the largest,and the path coefficients are 0.1080,-0.1778,-0.3680 respectively.With the increase of soil p H,the path coefficient showed an upward trend,from positive effect to negative effect.It shows that exchangeable Ca²⁺plays a certain role in the process of improving soil acidification by applying magnesium fertilizer,and with the increase of soil p H,exchangeable Ca²⁺and exchangeable Mg²⁺may have antagonistic effect.4.The application of magnesium fertilizer can quickly increase the contents of soil organic matter,nitrogen and total phosphorus,and increase the germination density of tea plants and the contents of tea polyphenols and water extracts from fresh leaves.Magnesium fertilizer(MG2 120kg·hm^-1)treatment significantly increased soil organic matter and total nitrogen in acidified tea garden in spring and summer,with an average increase of 17.7%～43.7%.Therefore,the application of magnesium fertilizer can improve soil fertility to a certain extent.The germination density of MG2 treatment increased significantly at the spring tea stage,with an average increase of 13.3%.MG2 treatment significantly increased the content of water extract in spring tea stage,with an average increase of 9.8%.Magnesium fertilizer(MG2 160 kg·hm^-1)treatment significantly increased the content of tea polyphenols in autumn tea period,with an average increase of 28.9%.Therefore,the application of magnesium fertilizer can improve the yield and quality of fresh leaves to a certain extent.In conclusion,the application of magnesium fertilizer can improve the soil acidification of tea garden.The main path is exchangeable Mg²⁺to increase the soil p H through the direct effect path,and then reduce the soil exchangeable Al³⁺through the indirect effect path to increase the p H.In addition,the application of magnesium fertilizer can increase the content of soil organic matter,nitrogen and phosphorus,and improve the yield and fresh leaf quality of tea to a certain extent.