Comparison of Phenolic Acids in the Soil of Replanted and No-Replanted Apple Orchards in Loess Plateau

Replant disease caused by autotoxic substances has become an important problem in apple production.Loess Plateau is a main apple production region of China.The composition and contents of phenolic acids in the soil of replanted and no-replanted apple orchards in Loess Plateau,including Linyi,Pinglu,Baishui,Luochuan and Yintai,were investigated and analyzed by HPLC.The results showed that the composition and contents of phenolic acids in the apple orchard soil of different regions and depth were significantly different.The contents of phenolic acids decreased slowly over time.Content of chlorogenic acid in 40-60 cm soil layer was1.5 times that in 20-40 cm soil layer,and 21 times that in 0-20 cm soil layer in Shanxi region.Phloridzin was not detected in 0-20 cm and 40-60 cm soil layers in Shanxi.There was no significant change in chlorogenic acid content in soil layers,and phloridzin was only detected in 40-60 cm soil layer in Shaanxi.Pyrogallic acid,chlorogenic acid and phlorizin were main phenolic acids in replanted soils.The content of pyrogallic acid,chlorogenic acid and phlorizin constitutes more than 66% of total content of phenolic acids in Shaanxi.