Impact of Fertilizers on Heavy Metal Loads in Surface Soils in Nzoia Nucleus Estate Sugarcane Farms in Western Kenya Solomon Omwoma • Joseph O. Lalah • David M. K. Ongeri • Maurice B. Wanyonyi Received: 26 April 2010 / Accepted: 28 October 2010 Ó Springer Science+Business Media, LLC 2010 Abstract Analysis of heavy metals in top soil samples from Nzoia sugarcane farms in Western Kenya found elevated levels of heavy metals in the soils with mean concentrations (mg kg -1 dry weight) of 142.38, 59.12, 73.35, 116.27, 409.84 (dry season) and 144.22, 50.29, 72.14, 158.81, 368.83 (wet season) for Cr, Pb, Cu, Zn and Fe, respectively, compared with a control soil sample from an adjacent field where fertilizers are not applied having mean concentrations of 117.27, 61.87, 63.68, 123.49, 282.93 (dry season) 108.00, 50.68, 66.10, 114.23, 167.01 (wet season), respectively. The heavy metal loads in the sugarcane farms were above international standards. The levels of the same metals in the fertilizers used in the sugarcane farms were within acceptable international standards. A risk assessment of the continued use of phosphate fertilizer (DAP) in the farms based on a 50-year period, did not exceed international threshold. The soil pH values (6.18 dry season and 5.66 wet season) were low compared to the control (7.46 dry season and 7.10 wet season) a situation that could accelerate heavy metal sol- ubility and mobility in the farm soil. Lowering of soil pH was attributed mainly to fertilizer application and partly to increased organic matter content as shown by the high mean total organic carbon content values of 8.63% (dry season) and 8.43 (wet season) in comparison with a control soil meant total organic carbon content value of 4.76% (dry season) and 5.02 (wet season). Keywords Heavy metals Á Fertilizer impact Á Sugarcane farms Á Nzoia Á Kenya Mortvedt (1995) has reported that fertilizers and biosolids, mixtures of scum and sludge, contain heavy metals that accumulate in soil with repeated fertilizer application. Heavy metals in fertilizers and other soil inputs are there- fore a big threat to the sustainability of farming practices and to the ecology of the local environment. The bioac- cumulation and bio-concentration of toxic heavy metal residues in the food chain can put terrestrial consumers including humans and birds at risk (Wang 1987; Gough and Herring 1993; Driscoll et al. 1994; Ongley 1996; Sekhar et al. 2003). The risks of heavy metal accumulation through agricultural activities and problems posed by heavy metals in fertilizers and other soil inputs have therefore increasingly drawn the attention of farmers, environmental organizations, consumers, and public poli- cymakers worldwide (USEPA 1999; Lawrence and Brian 2002; Oliver 2004; Pekey et al. 2004). The physicochemical processes taking place within the soil environment, including soil erosion, leaching, plant uptake and volatilization, are the primary determinants of the transport and fate of heavy metals emanating from fertilizers and related products (Alloway 1995a). Although heavy metals are not susceptible to chemical degradation like organic contaminants, chemical conditions in the soil are important secondary determinants of transport and fate of both anthropogenic and naturally-occurring heavy met- als (Duinker et al. 1982; Alloway 1995b; Ford et al. 2001). The four various physico-chemical interactions between S. Omwoma Á D. M. K. Ongeri Á M. B. Wanyonyi Department of Chemistry, Maseno University, P.O. Box 333, 40105 Maseno, Kenya J. O. Lalah (&) Department of Chemical Sciences and Technology, School of Applied Sciences and Technology, Kenya Polytechnic University College, P.O. Box 52428-00200, City Square, Nairobi, Kenya e-mail: josephlalah57@yahoo.com 123 Bull Environ Contam Toxicol DOI 10.1007/s00128-010-0133-7