Impact of nitrogen fertilizer applications on surface water nitrate levels within a Kenyan tea plantation
Department of Chemistry and Biochemistry, Pwani University College, P.O. Box 195, Kilifi 80108, Kenya; Department of Chemistry and Biochemistry, Chepkoilel University College, P.O. Box 1125, Eldoret 30100, Kenya; Department of Soil Science, Chepkoilel University College, P.O. Box 1125, Eldoret 30100, Kenya
Tea production in the Kenyan Rift Valley uses high rates of nitrogenous fertilizer. Nitrates can be discharged to water bodies through leaching and surface run-off. Nitrate levels above 10 mg/L NO3 - N cause methemoglobinemia which is fatal. A study to monitor changes in surface water nitrate levels was carried out in ten rivers within a Kenyan tea plantation for three years. Water samples were obtained before and after fertilizer application in 2004, 2005, and 2006. Nitrate-nitrogen (NO3 - N) was determined colorimetrically by the cadmium reduction method using HACH-DR 2400 dataloging spectrophotometer. For the three years, the highest nitrate-nitrogen levels were in river Temochewa in 2005 during the first fertilizer applications (4.9 mg/L to 8.2 mg/L). There was no established trend between surface water nitrate levels and the time of fertilizer applications; however, fertilizer application contributed to an increase in nitrate levels. The initial nitrate-nitrogen levels in most of the rivers were high, indicating that contamination could have been upstream; hence, further research is required to establish this. Nitrogen-nitrogen levels in the three years were below the maximum contaminant level of 10 mg/L NO3 - N; however, the rivers should be monitored frequently. © 2013 J. K. Maghanga et al.