Source and transport controls on nutrient delivery to tile drains

Apportioning sources, assessing flow pathways, and quantifying the interaction between source transport factors are critical for decreasing nutrient loss from agricultural catchments. In this study, water, nutrient, tracer (δ18O, electrical conductivity) fluxes were measured over two years a tile-drained field in Indiana, USA to quantify linkages among water management practices, delivery tile drains. Three-component hydrograph separation showed that discharge was, on average, sourced groundwater (65 ± 31%), shallow soil (10–20-cm deep; 29 28%), precipitation (6 8%). Daily nitrate-N (NO3-N) dissolved reactive phosphorus (DRP) load ranged 0.0 1.8 kg ha−1 0–101 g ha−1, respectively, while cumulative loads 30.7 1,040 ha−1. Nutrient practices (fertilizer rate, placement, timing) directly influenced magnitude of incidental proportion was derived fertilizer source. It estimated 52% 46% NO3-N DRP load, occurred within 30 d application. Continuous re-distribution throughout profile following application resulted broad range concentration across pathways antecedent conditions. contrast, dry conditions with or greater, but more variable, compared wetter when largely comprised groundwater. Findings suggest table dynamics exerted strong control concentration, as similar surface-tile hydrologic connectivity during both wet produced different quality outcomes. Groundwater may therefore serve chemical buffer concentration. Combined measurements revealed novel insights into processes controlling drains, direct applicability conservation practice implementation improving process representation models.