Nitrogen and phosphorus losses in surface runoff and drainage water after application of slurry and mineral fertilizer to perennial grass ley

Losses of nitrogen (N) and phosphorus (P) from perennial grass ley on a fine sand soil were studied with five treatments: no fertilizer (1), cow slurry applied in autumn (2), winter (3) or spring (4), and mineral fertilizer applied in spring (5). For N, the total amounts applied (1992-96) were 0, 772, 807, 805 and 510 kg ha(-1) and for P 0, 141, 119, 143 and 107 kg ha(-1), respectively. In the first year (establishment of the ley, 1992-93), N losses (drainage,ae + surface runoff) were slightly higher after application of slurry in autumn (with immediate ploughing, treatment 2) than in treatments 1, 4 and 5 (21 kg ha(-1) vs. 17 kg ha(-1)), but the respective P losses (0.7-0.9 kg ha(-1)) were not affected. During the Iey years (1993-96) the N and P losses were increased by surface application of fertilizers and by abundance of surface runoff (83-100% of the total runoff). Nutrient losses were extremely high after slurry application in autumn and winter, accounting for 11% and 33% of the applied N and 17% and 59% of the applied P, respectively. The N losses during the Iey years from treatments 1-5 were 13, 62, 191, 23 and 24 kg ha(-1), where the proportion of NH,-N was 21, 49, 56, 33 and 39%. The respective P losses were 0.73, 16, 54, 4.2 and 4.0 kg ha(-1), where the proportion of PO4-P was 52, 85, 77, 68 and 64%.