Transformations of Nitrogen Following the Application of 15 N-Labelled Cattle Urine to an Established Grass Sward

Cattle urine, labelled with 15 N urea, was applied in August 1987 at a rate equivalent to 74 g N m -2 to a series of confined microplots, inserted to a depth of 30 cm in a 16-year-old grass sward consisting mainly of perennial ryegrass (Lolium perenne). Contents of total N and 15 N were determined at intervals between 2 and 321 days after the application in a range of soil and plant components of the sward, and assessments were made of ammonia volatilization and denitrification (...)