Crop uptake and leaching of 15N applied in ruminant slurry with selectively labelled faeces and urine fractions

Two animal slurries either labelled with 15N in the urine or in the faeces fraction, were produced by feeding a sheep with unlabelled and 15N-labelled hay and collecting faeces and urine separately. The slurries were applied (12 g total N -2) to a coarse sand and a sandy loam soil confined in lysimeters and growing spring barley (Hordeum vulgare L). Reference lysimeters without slurry were supplied with15 NH415NO3 corresponding to the inorganic N applied with the slurries (6 g N m-2). In the second year, all lysimeters received unlabelled mineral fertilizer (6 g N m-2) and grew spring barley. N harvested in the two crops (grain + straw) and the loss of nitrate by leaching were determined.