In order to predict the long term effects of manure applications on soil nitrogen supply, this project will aim to quantify nitrogen mineralization from the organic fraction of farm manure applications. Nitrogen mineralization from selected farm manure treatments will be quantified at 3 sites (ADAS Gleadthorpe, ADAS Rosemuand, IGER North Wyke) which have contrasting soil properties (loamy sand, silty clay loam and sandy loam, respectively) and climatic conditions (annual rainfalls of 650, 800 and 1000 mm, respectively). Ammonium nitrogen stripped manures have already been applied to each of the 3 sites; 9 manure treatments that have been used include 2 each of cattle FYM, pig FYM and cattle slurry and 1 each of pig slurry, broiler litter and layer manure. Grass nitrogen uptakes and nitrate leaching losses will be determined, and then combined to give an overall nitrogen balance for each treatment as well as organic nitrogen decay curves for each manure. Associations between organic nitrogen mineralization and soil moisture and temperature conditions will be investigated. Field mineralization rates will be related to the manure organic nitrogen fractions that have already been determined by chemical extraction and pot incubation studies in project NT1501. The ability of existing models of manure nitrogen (e.g. NCYCLE, MANNER) to quantify manure organic N mineralisation will also be evaluated.