Agrochemical usage and environmental contamination: a case study of Agogo vegetable farming project in Ashanti Region of Ghana

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Date
2000-02-01
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Abstract
A survey was conducted at Agogo in the Asante Akirn North District of the Ashanti Region of Ghana to assess the perception, attitude and use of pesticides and fertilizers by farmers. The common pesticides used were Karate (Larnbdaccylathine) an insecticide: Thiodan (Endosulfan) an insecticide: Dithane (Mancozeb). a fungicide: Kocide (Cupric Hydroxide), a fungicide and Sammpi No 3, a fertilizer. All farmers interviewed used inorganic fertilizer and the only means to combat pest resurgence is by application of synthetic pesticides. Majority of them are semi-illiterate and the decision on amount of pesticide to he applied is based on the level of pest infestation. Turbidity of all rivers exceeded the W.H.O. guideline limits, while phosphate, nitrate and nitrite were not detected in any of the rivers. Alkalinity was far below the W.H.O. guideline value in all the rivers but its presence was significant with Kowire recording the highest level of 44.3 mg/I CaCO3. The mean levels of the heavy metals in water ranged as follows: Cd, 0.086-0.1 19mg/l: Pb. 0.18- 0.43mg/l: Zn, 0.25 0.40mg/l: Ni, 0.48- 0.59mg/l and Cu, 0.24 - 0.86mg/l. The mean Cd and Pb concentrations in water exceeded the W.H.O. guideline limits, while Cu and Zn were below the recommended safe values. Cadmium’ lead and zinc levels in sediment were higher than in unpolluted sediments, while copper was lower. Heavy metal residue in soil in both 0 - 15cm and 15 - 30cm depths were compared to levels reported for unpolluted arable soil. Cd, and Zn levels were above the guideline value reported for unpolluted arable soil. Pb and Cu were below, while Ni was within this range. Soil analysis of phosphorus recorded a range of 15.7kg/ha to 40.3/ha at pH range of 5.3 to 7.2, which is within the range of values reported in similar soils. Lead and cadmium concentration in the rivers were high above W.H.O. guideline hence the rivers were contaminated by these metals, so were sediments in their respective rivers. The soils were also contaminated with cadmium. It is recommended that Pesticides and heavy metals levels should be determined in some of the vegetables such as tomatoes, cabbages and aquatic biota. Also, Ministry of Food and Agriculture im collaboration with other relevant institutions should organize educational and training programmes on pesticides handling, application and proper farming practices for the farmers at Agogo.
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A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of Master of Science degree in Environmental Sciences, 2000
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