Evaluation Of Soil Environmental Suitability In Organic Tea Garden And Superior Region Division

Aiming at organic tea related standards and environmental certification requirements,the study on evaluation of soil environmental suitability for organic tea garden was carried out.Sampling scale,environmental suitability indexes and evaluation methods on organic tea garden were discussed in order to analyze the impact of environmental factors during tea production.By comprehensive quality evaluation of ecological conditions,soil fertility and pollution of tea gardens from different areas of south China,combined with local economic development,tea varieties and industrial scale,the study analyzed the soil and tea samples among different tea regions,defined the suitable region and superior region of organic tea production area in China,which could improve and standardize the organic certification technology system,provides scientific recommendations for regional development and rational layout of organic tea planting.Spatial differences of soil properties,such as organic matter content,heavy metal content and pH were analyzed under varying sampling methods,including depth,sample point layout and sample numbers among organic tea gardens.The results of soil environmental quality evaluation in tea gardens were significantly different under different sampling methods.Among different depths of soil profile,both organic matter content and pH changed significantly(p<0.05).The pH was lower and organic matter content was higher in 20～30 cm soil layer where most tea roots exist.Hg and Pb were from external sources and clustered in 0～10 cm soil layer,accounting 49.52%and 61.56%respectively.Recommended sampling depth of tea garden is 30 cm,as it reflects environmental suitability of tea garden soil more objectively.Soil indexes changed significantly(p<0.05)by different sampling densities.The order of spatial variation coefficient of heavy metals in the experimental tea gardens was as follows:Pb>Hg>Cu>Cr>As.At the range of different altitudes,soil of slope crest possessed higher organic matter content and lower pH value(p<0.01).It is recommended to use partition sampling method and increase sample numbers in order to solve the problem caused by spatial difference in large scale tea garden.Among 30 experimental tea gardens from different tea regions,the soil fertility condition was favorable.The soil integrated fertility indexes ranged from 0.70 to 0.99,which were in grade I and grade II according to soil fertility grading standard.The tea gardens in grade I accounted for 71.4%,and that in grade II accounted for 28.6%.The soil fertility condition in Jiangnan tea region was better than other regions.Soil organic matter content in different tea regions were presented as:Xinan tea region>Huanan tea region>Jiangnan tea region.The pH value in different tea regions were also presented as:Xinan tea region>Huanan tea region>Jiangnan tea region.Among 18 tea samples from different tea production areas,the heavy metal content did not exceed the limit of environmental standard.The over-standard rate of soil heavy metal,Hg in 30 tea gardens were 23.3%.Only one garden’s Pb content exceeded the limit.Through integrated index method evaluation,the soil environmental suitability results of experimental tea gardens were as follows:50.0%suitable,26.7%medium-suitable and 23.3%unsuitable.The El evaluation results of China’s southern tea region,including more than 1,400 counties were generally mediocre.The suitable,medium-suitable and unsuitable counties accounted for 66.1%,22.3%and 11.6%,respectively.Tea production conditions in different areas are quite different.Jiangnan tea region had obvious advantages over the other tea regions.In the four tea regions in southern China,the certified organic tea production enterprises were more than 1000,distributed in 312 counties.There were about 170 counties that retained over 5000 acres tea-planted area:Jiangnan tea region accounted for 54.1%,Xinan tea region accounted for 22.4%,Huanan tea region accounted for 15.3%and Jiangbei tea region accounted for 8.2%.In the superior tea region based on featured varieties,areas for planting green tea was more extensive,which could be in large-scale production among all four tea regions.The superior area for Oolong tea were all in the Huanan tea region.And the superior area for Pu’er tea were all in the Xinan tea region.