Title: Impact of agricultural activities on phosphorus in streams draining into Opa Reservoir Ile Ife, Nigeria

Authors: J.O. Olowoyo; I.E. Ofoezie; A.A. Amusan

Addresses: Department of Biology, University of Limpopo, Medunsa Campus, P.O. Box 139, Medunsa, Pretoria, 0204, South Africa. ' Institute of Ecology and Environmental Studies, Obafemi Awolowo University, Ile Ife, Osun State, 220005, Nigeria. ' Department of Soil Science, Obafemi Awolowo University, Ile Ife, Osun State, 220005, Nigeria

Abstract: Phosphorus is noted as the limiting factor of eutrophication. We investigated the impact of different agricultural land use (mixed cropping, horticultural garden and fallow land) on the phosphorus loading of a reservoir. Soil samples were analysed for pH, particle size distribution, organic matter, available P and erodibility index calculated. Water samples analysed for biological oxygen demand (BOD5), dissolved oxygen, phosphate, organic matter and pH. The result shows available phosphorus in the order: fallow land > mixed cropping > horticultural garden. The results suggest that the PO₄^3- in the reservoir maybe due to the effect of the cultivated land around the reservoir. The soil organic matter and available P shows significant patterns of seasonal and profile variations. To prevent runoff from agricultural land to the reservoir, the idea of zero cropping should be encouraged.

Keywords: phosphorus; erosion; reservoirs; land use; agricultural activities; agriculture; streams; Nigeria; water pollution; mixed cropping; horticultural gardens; fallow land; eutrophication; organic matter; soil contamination; runoff; zero cropping.

DOI: 10.1504/IJEE.2013.050891

International Journal of Environmental Engineering, 2013 Vol.5 No.1, pp.41 - 51

Received: 12 May 2011
Accepted: 28 Dec 2011
Published online: 07 Nov 2013 *

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