Effects of quality of irrigation water on the quality of selected vegetables in the Kumasi Metropolis

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October 2015
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The research was carried out in five vegetable growing locations in the Kumasi metropolis to assess the effects of the quality of irrigation water on the quality of three different vegetables which were cabbage, carrots and green pepper. The objectives of the study were to identify the quality of the sources of irrigation water used in vegetable cultivation and determine the effect the water has on the vegetables in terms of microbial and pesticide contamination, and also determine microbial load content of vegetables in some markets where vegetables from the study area are sold. A field survey was first carried out where one hundred and twenty respondents were interviewed. They comprised of vegetable farmers, vegetable sellers, vegetable consumers, food sellers, agrochemical sellers and agricultural extension officers. The results obtained showed that the sources of water for irrigating vegetables in the Kumasi metropolis are dugouts and rivers/streams. Some farmers treated the water before use (filter or add some pesticides). Vegetables are mostly harvested by vegetable sellers and carried to the market. From the results, most consumers wash their vegetables with salt solution while majority of food vendors wash vegetables with only water. Laboratory test was carried out on the irrigation water and the vegetables from the growing sites and markets to determine the pesticide residue and microbial load content. The results showed that, only DDT and chlorpyrifos were detected in the irrigation water in very low values while thirteen pesticide residues were detected in the vegetables from the field. Total coliform, faecal coliform and E-coli counts were also detected in the irrigation water, vegetables from the field and from the market. Irrigation water from KNUST had the highest total coliform count, while water from Ramseyer had the lowest. Also, carrot recorded the highest levels of total coliform, faecal coliform and E.coli, followed by green pepper and the lowest being cabbage. On the average, vegetables from Ramseyer had the highest total coliform, faecal coliform and E.coli levels while Kwadaso had the lowest total coliform and faecal coliform counts and KNUST recording the lowest E.coli count. The results also showed that microbial contamination is higher in vegetables from the markets than from the field which is also higher than that of the irrigation water. Dry matter and moisture content were also determined and it revealed that carrot contains 11.34% dry matter, green pepper contains 5.55 and cabbage contains 6.38%, this shows that really, vegetables contain more moisture than dry matter content. The study revealed that microbial and pesticide contamination of vegetables does not depend on only irrigation water.
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A thesis presented to The School of Research and Graduate Studies, Kwame Nkrumah University of Science and Technology, in partial fulfilment of the requirements for the award of the degree of Master of Philosophy (Mphil.) Postharvest Technology,
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