Impact of nitrogen fertilizer applications on surface water nitrate levels within a Kenyan tea plantation

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.