EFFECTS OF APPLICATION TECHNIQUE AND ANAEROBIC-DIGESTION ON GASEOUS NITROGEN LOSS FROM ANIMAL SLURRY APPLIED TO RYEGRASS (LOLIUM-PERENNE)

Ammonia volatilization and denitrification were measured in a ryegrass field in Denmark after direct injection and application with trail ho ses of an untreated cattle slurry and an anaerobically digested slurry in late May-early June 1993 and 1994. Ammonia volatilization was meas ured using a wind-tunnel system for a period of 8 days after slurry ap plication. Denitrification was measured for a period of 21 days after slurry application. In an adjacent field experiment, nitrogen-uptake ( N-uptake) was determined in the first two cuts of the ryegrass harvest ed after slurry application. N losses through ammonia volatilization w ere larger in 1993 than in 1994 due to differences in climatic conditi ons. Ammonia volatilization was lowered substantially (47-72%), when s lurry was injected compared with surface application. In 1993 the loss from surface-applied digested slurry was only 35% of total ammoniacal nitrogen (TAN), while the loss from the raw slurry was 47%. There wer e no significant differences in ammonia volatilization from the two sl urry types in the other experiments. N losses through denitrification were low (<2% of TAN), but there were clear differences in the losses, depending on slurry type, application method and experimental year. I njection of the slurry gave a larger N-uptake in the first cut of gras s compared to the trail-hose application. In 1993 N-uptake from the di gested slurry treatment gave significantly larger N-uptake compared to the raw slurry in the first cut.