Assessment of Groundwater Quality of Selected Inland Valley Agro-ecosystems for Irrigation in Southwest Nigeria
Keywords:southwest Nigeria, groundwater, wetland, agriculture, water quality indices
The study assessed the quality of groundwater of 6 inland valley (IV) agro-ecosystems with a view to establishing their characteristics for cropping in the derived savannah of southwest Nigeria. Water samples were collected in piezometers during the rainy and dry seasons and analysed for physicochemical and heavy metal properties. Major water quality indices and comparison with stipulated standards were used to determine the usability of the waters for irrigation. The study showed that the waters were generally neutral to slightly alkaline, with the dominance structure of the major cations and anions in the order of Na+ > Ca2+ > K+ > Mg2+ and Cl- > SO42- > HCO3- > CO3. The concentration of heavy metals was generally within the recommended limits for most crops grown in the study area. Major water quality indices (sodium adsorption ratio, soluble sodium percentage, total dissolved solids, permeability index, magnesium adsorption ratio, Kelly’s ratio and residual sodium bicarbonate) are generally within the levels acceptable for crop irrigation. Kruskal-Wallis H test (two-tailed) showed that there was no statistically significant difference in the water quality parameters/indices between the inland valley sites, P = 0.935. The groundwater of inland valley agro-ecosystems of the study area is generally suitable for agricultural utilisation.
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