Nitrate Transport in Agricultural Systems

The transport of nitrate in agricultural landscapes influences the loading of watercourses with reactive nitrogen, with implications for water quality and ecological status. Nutrient pollution of waterbodies is conceptualized by the source-pathway-receptor model. This chapter addresses the pathways of nitrate transport in agricultural settings. Transport occurs via overland, unsaturated, and groundwater pathways. The relative importance of each of these pathways depends upon landscape characteristics and climatic patterns, which vary regionally. Nitrogen behaves dynamically within transport pathways, subject to microbial cycling and hydrologic transport, concurrently. Transport is subject to the time lag, which delays the arrival of nitrate at receptors. Accounting for this delay is essential for interpreting the effects of past nutrient management practices and mitigation efforts. Time lag results from several factors, of which hydrologic and biogeochemical lags pertain directly to transport pathways. In this chapter, the principles of nitrate transport in each of these hydrologic pathways are discussed.