Leaching of Nitrate-N (NO3-N) from cropped and fallow soil - a lysimeter study with ambient and imposed rainfall regimes

Abstract

A three-year investigation into the effects of nitrogen (N) fertiliser rates and rainfall on nitrate-N (NO3-N) leaching from spring barley and Fallow was carried out in a lysimeter unit. The soil was well drained, moderately deep and similar to soils used to grow cereals in Ireland. Levels of fertiliser N applied were in the range 0-120kg per ha with rainfall amounts varying from 90 to 159 percent of ambient. The Fallow treatment resulted in large removals of N in the drainage water with high concentrations of NO3-N. The load of N removed in the water draining from the barley crop was, in general terms, related to drainage volume (R2=~0.7) while NO3-N concentrations, where N was applied, were inversely related to drainage volume (R2=0.6). Mean NO3-N concentration in drainage water from barley receiving fertiliser N was >MAC in two years out of three. The relative importance of the results to the designation of Nitrate Vulnerable Zones and possible mitigation strategies are discussed.