Soil Suitability Evaluation In Typical Tea Garden Based On The Analysis Of Fertility And Potential Ecological Risk Index

With the increasing demand for green life,the requirement of the quality of tea is accordingly higher.The soil quality of tea garden is the key factor affecting the quality of tea.However,with the extensive application of the tea garden input and the aggravation of the environmental pollution,the soil environmental quality of the tea garden has been deteriorating.Anxi county is the birthplace of Oolong tea,and it is one of the key tea producing counties in China.Therefore,a comprehensive understanding of the spatial distribution of the heavy metal and nutrient in the tea garden soil in Anxi County,as well as the suitability assessment and potential ecological risk assessment of tea garden are of great significance for soil improvement and green development of tea industry.78 points were sampled in the typical tea garden in Anxi County.The content of pH,OM,CEC,TN,TP,TK,AN,AP,AK,Cd,Pb,Hg,As and Cr were monitored for future evaluation.Based on these test data,multivariate statistical analysis and geostatistics methods were applied to propose the spatial distribution of the soil quality and fertility.The potential ecological risk index method was introduced to evaluate the heavy metal pollution in the soil of tea garden.Fuzzy comprehensive evaluation method was finally used to evaluate the soil suitability for the tea plantation based on soil quality and fertility index.The results show that:(1)The variation coefficient of soil nutrient indexes including CEC,TK,AK,OM,AN,TN,Ca and Mg could be ascribed to medium variation,while AP and TP belonged to strong variation.The spatial distribution of each index shows that,OM and CEC are gradually decreasing from the west to the east,while TN,TP,TK,AP and AK are gradually decreasing from the northwest to the southeast.The available Ca and Mg showed a wide distribution and local concentration status.The average IFI of the comprehensive fertility index is 0.70,which indicates that the soil nutrients in Anxi tea garden are classified as the second grade.The spatial distribution of fertility shows a trend of decreasing from northwest to southeast.(2)The content of organic matter in tea garden is rich.However,blind fertilization,poor mobility of P in soil and loss of K in acid soil cause the phenomenon of high N,P and lack of K in tea garden soil.It is suggested that measures such as Soil testing and fertilizer recommendation should be adopted to have it in control.The main reason for the low CEC content is the sandy property and the scouring of soil.Straw and biochar are suggested to be added in the soil to improve the aggregate structure.In view of the calcium and magnesium elements in the tea garden soil,the management plan of "deficiency based supply"should be adopted in order to avoid blind application.(3)The standard-reaching rate of Cd,Pb,Hg,As and Cr were 93.59%,98.72%,97.44%,100%and 98.72%,respectively.In spatial distribution,As and Cd show a downward trend from northeast to southwest,and Hg and Pb show a gradual increase from northeast to southwest.The content of Cr is distributed uniformly throughout the region.The average potential ecological risk index Eri of the 5 heavy metals was Cd>Hg>As>Pb>Cr.The average value of the integrated ecological risk index RI is 149.26.It shows that the heavy metal status of the tea garden in Anxi county is at the middle degree of ecological risk,and the spatial distribution is gradually decreasing from the northeast to the southwest.(4)In tea garden soil,Cd,Pb,Hg,As and Cr exceeded the background values to a certain extent.The percentage of sites exceeding the standard was 78.21%,64.10%,58.97%,38.46%,3.85%,respectively.Among them,Cd,Hg and Pb are in the form of non-point source pollution,and the pollution sources are deduced to be the application of pesticide,chemical fertilizer and organic fertilizer in the process of tea planting.It is suggested that the application of chemical fertilizer and pesticide should be rationally controlled and the organic manure can be applied to avoid secondary pollution.As and Pb,mainly from traffic,factory waste emissions and other human activities,have a small amount of accumulation.It is suggested that the layout of traffic and industrial land should be rationally planned,and the control of the source is strengthened so as to avoid the harm to the farmland as much as possible.The accumulation of Cr in the soil of tea garden is negligible.(5)The majority area of the tea garden soil in Anxi is suitable according to the suitability evaluation.The suitability grade is divided into 4 types,which are highly suitable,suitable,barely suitable and unsuitable.The proportion of their land area is 50%,29.49%,15.9%and 5.12%.The spatial distribution of suitability shows a trend of decreasing from west to east.The unsuitable regions are mainly located in the small part of Anxi,including southern part of Can’nei,the western part of Bailai,and the southwest of Hushang.