Plant N uptake and mineralisation were studied in a pot experiment using two soils of contrasting textures with a range of15N-labelled manures: poultry manure, cattle slurry, fresh swine manure, composted cattle manure, sewage sludge, straw, cabbage residues, pea residues and grass-clover turf. A range of manure and soil properties were determined before the incubations to examine if any combination of these properties would be useful to predict the amount and timing of N supply. Three replicate pots with and without ryegrass were used. Soil mineral nitrogen and ryegrass yield, N uptake and15N enrichment were measured throughout the 16 week incubation.