Nitrate leaching from a small, underdrained, grassland, clay catchment

Losses of nitrogen in the tile drainflow from a clay soil (Evesham series) under grazed grassland were monitored during the 1982/83 and 1983/84 drainflow seasons. In 1982/83, 40% of the discharge had a NO 3 − concentration > 11.3 mgNl −1 , while in 1983/84 concentrations were always > 20 mgNl −1 . Total N lost by leaching was 17.5 and 48.7 kg ha −1 in 1982/83 and 1983/84 respectively, which was equivalent to 9 and 43% of the fertilizer applied. The marked difference in N losses for the two seasons was attributed to differences in the quantity and timing of N fertilizer applications, the dryness of the preceding summer and the duration and density of stocking.