Evaluation Of Soil Quality In Typical Tea Producing Areas In Guizhou

In order to understand and grasp the current situation of soil quality in Guizhou tea gardens,this study took the soil of seven typical tea producing areas in Guizhou Province,including Leishan,Duyun,Kaiyang,Huaxi,Pu’an,Fenggang and Meitan as the research objects.Soil mechanical composition,bulk density,p H,organic matter,CEC,macronutrients,exchangeable calcium,exchangeable magnesium and other physical and chemical properties,as well as evaluation of soil acid phosphatase,sucrase,urease,catalase and polyphenol oxidase,etc.A comparative study of index determination analysis and index weight determination methods,using principal component analysis combined with Norm value to construct the minimum data set（Minimum data set,MDS）for soil quality evaluation,and evaluating the soil quality of typical tea-producing areas in Guizhou through the weighted sum method evaluation model.The purpose is to provide certain scientific guidance and theoretical basis for the planting and fertilization management,soil quality control and sustainable development of tea industry in the later stage of tea gardens.The main conclusions are as follows:（1）The soil bulk density in the study area was in a suitable state of tightness.There were significant differences in soil clay,silt and sand content in the same soil layer in different tea areas;the clay content was the highest（>50%）in Meitan and Huaxi,and the soil was relatively sticky.The soil p H was around 4.5,and there was an acidification trend in some areas.The soil nutrients are generally at a moderate and abundant level,and the contents of alkaline hydrolyzable nitrogen,total phosphorus and available potassium are relatively lacking in the soil layer of 20-40 cm in some tea areas.In the 0-20cm soil layer,the exchangeable calcium content of the upper soil of Huaxi and Fenggang was higher than the critical value(9.00 cmol·kg^-1),and the exchangeable magnesium content of Huaxi and Duyun was beyond the optimum range(0.25-0.75 cmol·kg^-1).The activities of soil sucrase,urease and polyphenol oxidase were all the highest in Duyi;acid phosphatase was the highest in Huaxi tea area and the lowest in Pu’an tea area,and soil catalase was distributed evenly in different tea areas.（2）MDS was established by PCA and correlation analysis combined with Norm value.The MDS in the 0-20 cm soil layer was soil bulk density,CEC,alkaline hydrolyzable nitrogen,total potassium,exchangeable calcium,acid phosphatase and polyphenol oxidase;The MDS in the 20-40 cm soil layer was clay,CEC,alkaline hydrolyzed nitrogen,total potassium,exchangeable calcium,sucrase and acid phosphatase.Four objective weight determination methods,W_Fi,W_Ri,W_Ciand W_ξi,were compared and studied,and it was more appropriate to use W_Ri to determine the weight of soil quality evaluation indicators in typical tea producing areas in Guizhou.The weights of MDS bulk density,CEC,alkaline hydrolyzable nitrogen,total potassium,exchangeable calcium,acid phosphatase and polyphenol oxidase in the 0～20 cm soil layer are 0.213,0.225,0.193,0.157,0.044,0.093,0.075,respectively;20-40 cm The weights of soil layer MDS clay,CEC,alkaline hydrolyzable nitrogen,total potassium,exchangeable calcium,invertase and acid phosphatase were0.181,0.140,0.142,0.186,0.048,0.176 and 0.127,respectively.（3）SQI（A）-TDS was positively correlated with SQI（A）-SDS（R²=0.902**）,SQI（A）-MDS（R²=0.579**）,the established important data set indicators and the MDS established by PCA and correlation analysis combined with Norm value can better replace TDS for soil quality evaluation.The main limiting factors of soil quality in the study area were soil bulk density,alkali-hydrolyzed nitrogen,total potassium and enzyme activity,and soil quality decreased with the increase of soil depth.The soil quality in the study area was mainly at medium and high levels,but there were certain spatial distribution differences,and the soil quality in some tea areas was at a low level.To sum up,the soil quality in the study area was generally at the medium level or above,but there were certain differences in space.A small number of tea gardens lack soil nutrients and have low soil quality.In the future,while vigorously developing tea plantation,we should pay attention to the quality of deeper soil,strengthen soil fertilization,apply organic and inorganic fertilizers in combination,pay attention to the input of nitrogen,phosphorus and potassium fertilizers.At the same time,we should pay attention to adjusting the p H value of the soil,and apply correctors in a timely manner to prevent soil acidification.