Effects of water pollution on soil physical and hydrological properties of a valley bottom at the University of Ibadan, Ibadan, Oyo State, Nigeria

ABSTRACT: Unpredictable rainfall patterns and climate change has lead to high competition among different water-use sectors vis-a-vis its decreased allocation to irrigation. The use of valley bottoms for agricultural production is also prone to the pollution of soil and waters in these valleys form various sources. Therefore, the effects of water pollution on soil physical and hydrological properties of a valley bottom were evaluated during 2010 dry season at the Agricultural students’ Practical Year Training Farm within the University of Ibadan, Ibadan, Nigeria. Geo-referenced ground and surface water samples and soil samples were collected from the field and analyzed for their physical and chemical properties. Soil samples were also collected from the river sediments and analyzed for their relative distribution of Sand, Silt and Clay fractions. All soil, water and vegetable plants collected from the field were also analyzed for their metal contents. Collected data were compared with World Health Organization (WHO) and Federal Environmental Protection Agency (FEPA) standards to assess the level of pollution in the valley bottom Pollution to surface water comes from drainage and sewage channels alongside remnants from adjacent recently constructed roads. The physical and chemical properties of the surface water shows a high concentration of sodium ion, and Sodium Adsorption Ratio (SAR) with values ranging from 29mg/l to 3400 mg/l and SAR values of 5.2 meq/l to 439.8meq/l respectively. However, ground water samples have a lower sodium ion concentration of 38.2mg/l to 605mg/l and a mean SAR value of 6.9meq/l. A Biological Oxygen Demand (BOD) value range of 105mg/l to 279.2mg/l was recorded alongside with TSS of 357.6mg/l to 978.5mg/l. The turbidity, total dissolved solids trend is in the same direction with BOD and Total Suspended Solids (TSS). The soil expressed a high total porosity that shows no correlation with volumetric moisture content. Recommendations for the prevention of pollution of surface water to ensure sustainable agricultural land resources management of valley bottom were suggested.