EFFECT OF ROCK PHOSPHATE AND COW DUNG ON THE HEAVY METALS CONCENTRATION IN Amaranthus viridis LINN GROWN IN A FIELD

Anwadike B. C.

Department of the College of Education, Warri, Delta State, Nigeria.

Author’s Email address ✉: anbenj@yahoo.com

Accepted January 22, 2020

This research work investigated the effect of application of rock phosphate (RP) and different rates of cow dung manure on heavy metals uptake in Amaranthus viridis collected from experimental and control sites in Ile - Ife, Nigeria. The residual concentrations of the elements such as lead (Pb), cadmium (Cd), zinc (Zn), copper (Cu) and arsenic (As) in the crop following the treatments were calculated as the transfer factor (TF). A total of 18 subplots containing the crops were treated with the fertilizers and the treatments consisted of RP alone; RP + 1.0 tha^-1; RP + 2.0 tha-1; RP + 3.0 tha^-1RP + 4.0 tha^-1 and minus RP and cow dung as the control. The experimental design used was the Randomized Complete Block Design (RCBD) which consisted of a control and the treatments had PR added singly and in a combination with different levels of cow dung. All the treatments were replicated thrice. Composite topsoil samples were collected using the Dutch soil auger while the plant leaves were collected pre-flowering; both were subjected to routine analyses for heavy metals using Atomic Absorption Spectrometer (AAS). The results showed that PR application alone and in combination with various levels of cow dung increased the soil solution concentrations of Pb, Zn, Cu, As and Pin the soil but were below the recommended standard by WHO and USEPA. Except for Cd the enrichment of the topsoil with heavy metals were not above the normal and critical value. Cadmium had a high value of 5.30µgg^-1 which was above the critical value of 3.0 µgg^-1. The heavy metals content of the plant under different treatments showed that Pb content did not increase with treatments. The study further revealed a high transfer ratio (TR) of heavy metals between soil and Amaranthus sp and ranged from Pb (1.72 -1.86), Zn (0.22 -0.67), Cu (14.38 -29.8), Cd (0.16 -0.32) and As (0.9 -2.1). The Cd concentration in the crop was negatively correlated (r = -0.51, p< 0.05). It can be concluded that both RP and cow dung contributed significantly to soil and crop contamination with heavy metals.

Key words: Rock phosphate, Cow dung fertilizer, Heavy metals, Amaranthus viridis

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