delta15N values of plants and soils in tea fields treated with commonly-used fertilization and rapeseed meal.

摘要

The nitrogen dynamics in tea fields were investigated using delta15N as the indicator of nitrogen sources and nitrogen metabolisms. There were two fertilizer treatments, rapeseed meal only and commonly used fertilization (rapeseed meal during springand autumn and chemical fertilizers during summer). The deltaN15 fertilizers used were: -1.0o/oo in ammonium sulfate, -0.8o/oo in ammonium nitrate and +5.3o/oo in rapeseed meal. The delta15N values of soils in the 0-20 cm layer were similar in both of the fields, and those in the 20-40 cm layer were higher by～1o/oo in the field treated with rapeseed meal. The delta15N values of soil solution in the rapeseed meal field were higher by～7o/oo , and those in the upper layers of the fields treated with commonly-used fertilization were lowered by the application of chemical fertilizer. The delta15N values of the tea plants reflected those of the soil solutions, higher in the rapeseed meal field. Generally, the delta15N values of the tea plants were lower than the averages of those of the soil solutions, probably due to the rapid uptake of chemical fertilizer nitrogen and also due to isotopic fractionation during the uptake of nitrogen from the soil solutions. The variation of delta15N values in differenttea organs suggested the fractionation of nitrogen isotopics during metabolism and translocation of nitrogen in the plants.