Lysimeter Study of the Fate of Nitrogen in Animal Urine Applied to Flood-Irrigated Pasture

The fate of nitrogen (N) in animal urine returns to flood irrigated pasture was studied using large soil monolith lysimeters (800 nun diameter x 1200 mm deep). Over a period of I year, the largest fraction of applied 15N (44%) was recovered by the pasture plants. The total amount (42 kg N/ha) and average peak concentration of N, in the leachate (42 µgN/ml) were less than values reported for many: other agricultural situations (e.g., ploughed pasture). The amount of N lost by denitrification was high (28% of applied 15N) and attributed to the wet soil conditions which prevailed. The amount of N remaining in the soil after 1 year (20% of applied 15N) was found mostly in the topsoil.