Nitrate Leaching and Drainage from Annual and Perennial Crops in Tile‐drained Plots and Lysimeters

Abstract

AbstractLeaching of NO3 with drainage water from tile‐drained field plots and from three types of lysimeters was estimated during a 4‐yr period. Treatments included barley (Hordeum distichum L.) with and without N‐fertilizer, a grass ley (Festuca pratensis), and a lucerne ley (Medicago sativa) (i.e., 4‐yr forage crops). The maximum amount of NO3 leached was 36 kg N ha−1 yr−1 for barley fertilized with Ca(NO3)2 (120 kg N ha−1 yr−1). For unfertilized barley the corresponding amount was 5 kg N ha−1 during the same period. The NO3 fluxes from the grass and lucerne leys were mostly below 5 kg N ha−1 yr−1. However, after the grass ley was plowed, considerable leaching occurred, reaching 42 kg N ha−1 during 20 weeks following plowing. Weather conditions had a strong influence on the temporal distribution of leaching losses. Lysimeters, compared with tile‐drained plots, had generally higher drainage volumes. The slow dynamics of groundwater beneath the drainage‐tiles can explain most of this difference. Lysimeters with disturbed soil profiles usually had higher drainage volumes than lysimeters with undisturbed profiles. Despite these differences, all methods consistently estimated the relative differences between the cropping systems concerning leaching of NO3. The degree of variation in drainage flow between lysimeter replicates was also satisfactorily low.