Accumulation of essential mineral and toxic trace elements in crops and soils of vegetable cropping systems in central highlands of Sri Lanka

Vegetables are widely cultivated in high rainfall and mountainous regions in Sri Lanka with poor soil conservation practices. Accumulation of essential mineral and toxic trace elements in the soils and widely cultivated vegetables of this region are poorly understood. One hundred soil and vegetable (i.e. cabbage, carrot and potato) samples were collected at the time of harvest and analysed for element concentrations. Soils contained high concentrations of essential mineral (N, P, K, Cu, Zn and Mn) and toxic trace elements (As, Cd and Pb). When comparing edible parts, cabbage contained the highest concentrations of mineral and toxic trace elements, and potato contained the lowest. Irrespective of the crop, edible parts contained high concentrations of N, P, K (14-35, 2-6, 15-24 g/kg, respectively), and Cu, Zn, Mn (2.5-6.7, 11-30, 8-147 mg/kg, respectively). Vegetables also contained As, Cd and Pb (0.04-1, 0.02-0.15, 0.02-0.26 mg/kg, respectively), but did not exceed the maximum permissible limits. Irrespective of the crop, 36-64 kg N, 6-11 kg P and 35-45 kg K per ha were removed with the harvest. According to the current rate of vegetable consumption by Sri Lankans (i.e. 240 g fresh weight (FW) per day), per capita consumption of 0.05-0.2 mg Cu, 0.45-0.65 mg Zn and 0.5-2 mg Mn per day through these vegetables was observed, i.e. 5-23% Cu, 7.5-11% Zn and 22-87% Mn of the recommended daily intake. Vegetables grown in the region served as a key source of essential mineral elements. However, agronomic mitigation strategies are needed to improve soil health and sustainability of these cropping systems.

Automated summary

Vegetables are widely cultivated in high rainfall and mountainous regions in Sri Lanka with poor soil conservation practices. The accumulation of essential mineral and toxic trace elements in the soils and cultivated vegetables are poorly understood. The soil samples contained high concentrations of essential minerals and toxic trace elements, while the edible parts of cabbage had the highest concentrations and potato had the lowest. The vegetables analyzed contained high concentrations of essential minerals and trace elements, but did not exceed the permissible limits.