Identification of Allelochemicals responsible for soil degradation in continuously cropped Tea plantations

Rhizosphere soils from Tieguanyin tea plantations of 0, 3, 9 and 25 years old wereextracted and eluted through 5 resins of different polarity. Tea seedlings were then grown withthe 5 eluents and their effects were determined on the photosynthetic indices and leaf quality.Among the 5 resins, soil eluents through ADS-7 resin most strongly inhibited the root length andheight of the receptor lettuce, photosynthetic indices and leaf quality of new tea plants. And theinhibitory effects increased with soil age, especially, the ADS-7 resin eluents from 25-year-oldsoil showed the strongest inhibitory effect. The GC-MS analysis of ADS-7 resin eluents showedthe presence of amides, esters, acids and other types, which changed significantly as the tea plantsoil age increased, and the content of all acids increased significantly, while the phenolic ketonecontent of all soil samples remained unchanged.