Abstract:
Weeds compete with tea mostly for light, water, and nutrients, which have a variable
impact on the yield of tea. Herbicide use is the most famous method in tea plantations
to control weeds. Glyphosate is a widely used herbicide in tea plantations to control
weeds. However, its excessive use may increase human exposure to heavy metals. Thus,
the prime aim of this study was to determine the levels of Copper (Cu), Zinc (Zn),
Nickel (Ni), Chromium (Cr), Iron (Fe), Manganese (Mn), Lead (Pb), and Cadmium
(Cd) in tea soils, fresh tea leaves, and black tea leaves (processed) of both herbicidesapplied
tea plantation plots and herbicide-free tea plantation plots in Sri Lanka. Metal
contamination levels were determined using Atomic Absorption Spectrometer (AAS)
after sample preparation was carried out using the Microwave Digestion System. The
data were statistically analyzed using the student’s t-test (95% confidence interval) to
compare the difference in metal concentrations between herbicide-applied and herbicidefree
tea plots. According to the obtained results, available Fe, Ni, and Pb levels of soils
of herbicide-applied tea plantation plots are significantly higher (p<0.05) than the soils
of herbicide-free tea plantation plots. Further, the Fe level in the soils of herbicideapplied
plots exceeds the maximum permissible limit (50000 mg/kg) according to the
World Health Organization (WHO). Furthermore, Zn and Pb levels of fresh tea leaves
in herbicide-applied plots are significantly higher (p<0.05) than those in herbicide-free
plots. In addition, Cr and Pb levels of black tea leaves were significantly higher (p<0.05)
in herbicide-applied plots. Overall, it can be concluded that the long-term application of
glyphosate in tea plantations has an impact on heavy metal accumulation in soil and tea
leaves. Therefore, it is important to practice integrated weed management techniques
to reduce herbicide use in tea plantations.
