Soil toxicity and microbial community structure of Wuyi rock tea plantation

The effects of tea soils of 4-, 14-, 28- and 32-planted years on tea photosynthetic indices and the protective enzymes [superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and malondialdehyde (MDA)] activities of replanted tea leaves were examined. It was found that these activities decreased significantly with increase in planted years. The MDA levels increased significantly with increase of soil planted years. The levels of polyphenols, caffeine and free amino acids in tea leaves were lower in tea seedlings grown in 14-, 28- and 32-years soils than in 0- and 4-year soils. In laboratory bioassay, the aqueous soil extracts inhibited the lettuce (Lactuca sativa L.) growth significantly with increased number of planted years. The contents of three phenolic acids (protocatechuic acid, p-hydroxybenzoic acid and cinnamic acid) were significantly higher in 14-, 28- and 32-year soils than that in 0- and 4-year soils. The microbial community of tea soils varied significantly than control. These results confirmed that soil toxicity exists in older tea soils of Wuyi rock tea area. The accumulation of phenolics, deficiency of carbon sources and change in the microbial communities appeared to be the main characteristics of older tea plantation soils.