STUDY OF THE EFFECTS OF CHEMICAL FERTILIZERS AND HERBICIDES ON THE LEVELS OF SOME HEAVY METALS AND ANIONS IN SOILS AND CORN (ZEA MAYS) GROWN IN SELECTED PARTS OF BENUE STATE, NIGERIA

¹J. Abah; ²F.I. Abdulrahaman and ²N.P. Ndahi

¹Department of Chemistry, Benue State University, Makurdi, Nigeria

²Department of Chemistry, University of Maiduguri, Maiduguri, Borno State, Nigeria

E-mail: abahjim@yahoo.com

ABSTRACT

This study employed standard laboratory procedures to determine the effects of the uncontrolled applications of chemical fertilizers and  herbicides on the levels of some heavy metals and anions in soils and corns (Zea mays) grown in some farms in Otukpo, Ohimini and Katsina-Ala Local Government Areas of Benue State, Nigeria between April and August, 2010. Levels of the heavy metals and anions in the samples were determined using an SP Pye (1900) Unicam Atomic Absorption Spectrophotometer equipped with air–acetylene burner and UV-Visible Smart Spectrophotometer (2000) respectively. Results of the concentrations of heavy metals in the corns of white maize varied between 0.016±0.001µg/g Co to 1.613±0.810µg/g Fe while a record of 0.019±0.003µg/g Co to 1.420±0.150µg/g Fe was obtained in the corns of yellow maize. The concentrations of the anions ranged from 30.18±3.91µg/g NO₂^– to 2511.18±1.03µg/g PO₄^3- in white maize corns and 28.45±1.35µg/g NO₂^– to 2705.03±5.01µg/g PO₄^3- in corns of yellow maize. Within 0-10cm of the soil depth, the heavy metals concentrations varied between 0.061±0.002µg/g Cr to 4.780±0.410µg/g Pb while the anions levels varied between 25.09±1.82µg/g NO₂^– to 400.83±1.16µg/g PO₄^3-. 10-20cm soil depth recorded higher concentrations of the heavy metals and anions. Both the levels of the heavy metals and anions were significantly (P < 0.05) higher in corns and soils obtained from farmers’ fields than the values recorded in samples from the control farms cultivated in each of the sample locations. However, these concentrations were lower than the WHO/FAO’s dietary permissible limits. The elevated levels of the heavy metals and anions in farmers’ fields suggest that the farmers should be trained to adopt better management of the applications of these agrochemicals in maize cultivation.

Key words: Corns, Agrochemicals, Heavy metals, Anions, Farmers’ Fields.