Abstract:
A study was conducted in 2009 to investigate the distribution of nutrient elements in cultivated and uncultivated soils, and sediments of surrounding Okai and Kwanta streams in Abiriba, Abia State of Southeastern Nigeria with the intention to determine the impact of agricultural practices on the water quality of these streams. The Okai stream was surrounded by a three-year old fallow land dominated by oil palm (Elaeis guineensis), raphia palm (Raphia spp), cocoyam (Colocasia esculentus), avocado tree (Persea Americana), shrubs (mainly Sponelias munibin) and sparsely distributed grasses. The upland farm close to this stream was grown to cassava (Manihot esculenta), pepper (Capsicum spp), and yam (Dioscorea spp). The Kwanta stream was located near a six-year old fallow land with a scanty bush predominantly composed of bamboo tree (Bambusa spp), oil palm (Elaeis guineensis), shrubs and grasses. The upland around this stream was a cultivated cassava farm. Crop rotation was the only means of replenishing used nutrients. Three sediment samples were collected at random at three points within the edges of each stream, bringing the total number of sediment sample to six. Three soil samples were collected randomly at two depths (0-20cm and 20-40cm) within the cultivated as well as the uncultivated farm, giving a total of 24 soil samples. Physical (particle size distribution) and selected chemical laboratory analyses were carried out on the soil and sediment samples. As the results showed, though both soils were generally low in nutrient elements, the Kwanta soil was a little more fertile than that of Okai. The cultivated soils were richer chemically than the uncultivated soils at both Okai and Kwanta sites. The nutrient load of Kwanta stream was higher than that of Okai stream, and this translated into more eutrophication in the former than in the latter. The sediments from the two streams were sandy, while the cultivated and uncultivated soils from the two study locations were loamy sand in texture. The soils from the sites varied (P < 0.05) significantly in Na and CEC values, while the sediments from the two streams showed significant difference (P < 0.05) in K and H contents. The soils of Okai and Kwanta farms are similar to the sediments of their respective streams in terms of chemical properties; this implies that the agricultural activities in the study area exerted some influence on the sediment and water quality of nearby streams.
