Health Risk Assessment of Amaranthus Species Grown on Inorganic and Organic Fertilizers

Abstract

Human health and environmental issues associated with intensive and vastly industrialized agriculture is the main cause of the constantly growing interest in organic farming. The objective of this study was to assess the heavy metals (Cd, Cr, and Pb) in Amaranthus cruentus (AC) and Amaranthus spinosus (AS) grown on organic fertilizer (poultry droppings (PD)) and mineral fertilizer (NPK 15:15:15). The seeds of AC and AS were sown separately in a pot containing 5kg soil. Each Amaranthus variety consisted of these treatments: control (C), organic fertilizer (PD) and mineral fertilizer (NPK 15:15:15); all laid out in completely randomized design and replicated four times. Pre physico-chemical properties and heavy metals of the experimental soil and treatments were analyzed using standard procedures, also Health Risk Index (HRI) was determined. Application of NPK at 4g/5kg soil and PD 10g/5kg soil was done and left for 7 days for better nutrient mineralization. Plants were thinned to 2 stands per pot after two weeks-after-sowing (WAS). Parameter(s) on growth were taken at 2, 4, and 5-WAS, while that of yield at harvest was done at 5-WAS. Data were analyzed using Analysis of Variance (p<0.05). Results showed significant differences (p<0.05) in growth parameters from A. cruentus and A. spinosus at 2, 4 and 5 WAS across all treatments (C, PD and NPK) applied. Results obtained at 5WAS showed the control with highest leaf area (34.13 cm2) from A. spinosus, while PD had 29.45 cm2. Also, A. cruentus treated with poultry droppings and control had 30.00 cm2 and 27.48 cm2, respectively. At fresh weight (yield) A. cruentus had the highest value (259.00g) treated with NPK compared to PD (167.75 g) and control (129.75 g), while A. spinosus had 179.75 g treated with NPK compared to control (162.75 g) and PD (135.75g). The control had high total dry weight of 35.50g from A. spinosus and 28.50g from A. cruentus. This study showed that NPK applied 4g/5kg soil gave the best performances in growth, fresh and dry matter yield in A. cruentus when compared to A. spinosus. Heavy metals result showed that Cd concentration was not detected in soil, root and shoot samples of A. cruentus and A. spinosus. Chromium levels were within the FAO/WHO (2001) tolerance level (Cr = 0.2 mg/kg), while concentrations of Pb were exceedingly higher in root and shoot samples of A. cruentus and A. spinosus above the permissible level (Pb = 0.3 mg/kg) in NPK treatments than poultry droppings. The HRI of Cr for A cruentus in root was<1 in poultry droppings and NPK 15:15:15, while Pb >1 in poultry dropping treatments of root and shoot. Consumption of vegetables with remarkably high contents of Pb especially in NPK 15:15:15 plots and high values of the Health Risk Index in poultry droppings should be well considered by the populace. Monitoring of vegetables grown on both organic and mineral fertilizers is required for quality food and safety.