Evaluation Of The Essential Trace Metals In Soils And African Spider Plants: Case Study Of Molo Ward-Nakuru County

Abstract

In Kenya, cases of malnutrition and nutritionally related ailments have been on the rise. This calls for the search of food crops with vital trace elements constituting their diets. The aim of the current research was to assess the concentrations of the Zn, Fe, Cu, and Mn in stems and leaves of the African Spider plant (Cleome gynandra). The trace metals were also determined in the soils from highlands and lowland regions in Molo Ward, Kenya, in which the Spider plant was grown. In addition, the pH levels in soils were determined. Both the plant and soil samples were analyzed using an EDXRF spectrometer. Fe was found to be the most abundant trace element in the soils with a concentration trend of Cu < Zn < Mn < Fe being observed. The mean concentration for the elements in the soil samples ranged from 63000 to 77000 mg kg-1for Fe, 3100 to 3600 mg kg-1 for Mn, 19 to 21 mg kg-1 for Cu, and 180 to 260 mg kg-1 for Zn. There were no notable distinction in concentrations of these elements in the two study regions (P > 0.05) given in Appendix 16. The soils in the area of the study were found to be slightly acidic with a mean range of pH 5.2 to 6.3. The Spider plant stems grown in the Highland were found to contain total available Zn at 160 ± 50 mg kg-1, Mn at 400 ± 140 mg kg-1, Cu at 16 ± 5 mg kg-1 and Fe at 4100 ± 1600 mg kg-1 while the leaves contained Fe at concentration mean of 3100 ±180 mg kg-1, Mn at 380 ± 120 mg kg-1, Cu at 14 ± 4 mg kg-1, and Zn of 225 ± 60 mg kg-1 respectively. For the Spider plants grown in the Lowland, the stem was found to contain Fe of 5600 ± 2100 mg kg-1, Zn at 140 ± 5 mg kg-1, Mn at 500 ± 20 mg kg-1, and Cu at 15 ± 6 mg kg-1 at while the leaves were found to contain Fe at 2200 ± 800 mg kg-1, Zn at 230 ± 60 mg kg-1, Mn at 350 ± 70 mg kg-1, and Cu at 13 ± 3 mg kg-1. There was no correlation between the pH and the essential trace elements in the soils in the present study (P < 0.05) given in Appendix 10. In comparison to the recommended daily dietary requirement, the Spider plants was found to provide enough amounts of Fe, Zn, Cu, and Mn thus making it a nutritious traditional vegetable (WHO,2005). Therefore, farmers should be encouraged and empowered to grow more of the vegetable.