, Volume 127, Issue 1-4, pp 389-401

Linking Water Quality with Agricultural Intensification in a Rural Watershed

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Abstract

Agricultural intensification was linked to streamwaterpollution in a case study watershed using GIS andnutrient budgeting techniques. The results showed thatsurplus nitrogen applications from fertilizers andmanure averaged 120 kg ha-1 yr-1. In some parts of the watershed surplus applications exceeded 300 kg ha-1 yr-1. A consistent increase in pig and chickennumbers (59 and 165% increase between 1986 and1996) is considered the main reason for the surplus.Water quality was impacted in two ways: nitratecontaminated groundwater contributed to high nitratesin a major tributary during the summer, while in thewet winter season ammonia, phosphate and coliformlevels were high throughout the drainage system.Significant negative relationships were found betweensurplus nitrogen applications and dissolved oxygenwhile ammonia and nitrate concentrations during thewet season were positively correlated to surplusapplications. Soil texture and drainage type were alsosignificantly correlated with the water qualityindicators suggesting that it is possible to use thebudget/GIS linked techniques for pollution riskassessment from agricultural non-point sources.