Morphology And Availability Of CNPK In Soil Profile Of Tea Gardens In GuiZhou

In this study,the yellow soil of the main tea region in Duyun City,Leishan County,Kaiyang County,Meitan County,Fenggang County,Pu’an County and Huaxi District of Guizhou Province was selected as the research object.The soil,residual branches and tea buds of tea garden profiles were collected in November 2019,and the different forms of soil carbon,nitrogen,phosphorus and potassium,basic physical and chemical indexes,and the full amount of plant carbon,nitrogen,phosphorus and potassium were determined.The carbon,nitrogen,phosphorus and potassium forms and availability distribution of soil profile in tea garden were studied to provide theoretical reference for nutrient management and improving tea yield in tea garden.The main conclusions are as follows:（1）Soil total phosphorus and available phosphorus decreased layer by layer.The inorganic organic phosphorus in soil profile were mainly A1-P（aluminum phosphorus）and Fe-P（ferrophosphorus）,MPo（moderately active organic phosphorus）and MRPo（moderately robustness organic phosphorus）in tea garden,and O-P（closed storage phosphorus）and Al-P in forest land.The available phosphorus sources were Fe-P（forestland）and MPo（tea garden）in topsoil,Al-P in 20-40 cm soil layer,LPo（high active organic phosphorus）and Al-P in 40-60 cm soil layer and Al-P in 60-100 cm soil layer.The potential phosphorus sources were Al-P（forestland）,MRPo,total phosphorus and Po（tea garden）,HRPo（high robustness organic phosphorus）and MRPo in 20-40 cm soil layer,Ca-P and HRPo in 40-60 cm soil layer and HRPo in 80-100 cm soil layer.phosphorus in residual branches affected HRPo and Ca-P in 60-80 cm soil layer of tea garden and Ca-P in 80-100 cm soil layer,O-P in 20-40 cm soil layer and Ca-P in 40-60cm soil layer of forest land.Pi（inorganic phosphorus）in topsoil,Al-P in 20-80 cm soil layer and AP in 80-100 cm soil layer affected tea P.（2）The soil available K（AK）,water soluble K（WK）and exchangeable K（PK）in tea garden decreased layer by layer,and 0-20 cm>20-40 cm（p<0.05）,and were generally higher than those in forest land.TK in tea garden showed an increasing trend below topsoil and was significantly higher than that in forest land.The highest availability potassium sources were WK in 0-60 cm soil layer and PK in 60～100 cm soil layer.The available potassium sources were TK gently available potassium（DK）in the soil layer of 20-40 cm,DK in the soil layer of 20-60 cm and80-100 cm in the forest layer.PK in 0-20 cm soil layer,TK and AK in 20-40 cm soil layer,TK in40-80 cm soil layer in tea garden,organic matter in 0-60 cm soil layer and PK in 60-80 cm soil layer in forest land.（3）Soil total nitrogen（TN）and alkali-hydrolyzable nitrogen（AN）showed a decreasing trend layer by layer,and in the soil layer below 40 cm,the total nitrogen in tea garden was less than that in forest.AN,ammonium nitrogen（NH₄⁺-N）and nitrate nitrogen（NO₃^—-N）content was significantly higher than that in 20-40 cm soil layer.NH₄⁺-N in 40-60 cm soil layer of tea plantation,0-40 cm soil layer and 60-80 cm soil layer NH₄⁺-N and NO₃^--N in 80-100 cm soil layer NO₃^--N and NH₄⁺-N is significantly correlated with AN,NH₄⁺-N is the nitrogen source that can be easily absorbed and utilized by tea trees in the soil profile,and TN in the soil layer of 20-40 cm in tea garden and 0-80 in forest land is the potential nitrogen source that can be utilized by plants.（4）Soil active organic carbon components decreased layer by layer,and NLC（inert organic carbon）and LC（medium active organic carbon）were the main components.Soil organic matter in tea garden was higher than that in forest land.The LC and LLC in 0-40 cm soil layer,LLC in40-60 cm soil layer,NLC and LLC in 60-100 cm soil layer were significantly correlated with VLC.LC is the most active carbon source in tea garden soil,while LLC and NLC in 80-100 cm soil layer are potential active carbon sources.In conclusion,the total carbon,nitrogen,phosphorus and potassium contents and available nutrients of yellow soil in Guizhou tea gardens decreased in the profile,including Al-P,WK and NH₄⁺-N,LC and PK are the most available nutrients for plants in soil layers.