The Journal of Agricultural Science

Crops and Soils

Effects of application technique and anaerobic digestion on gaseous nitrogen loss from animal slurry applied to ryegrass (Lolium perenne)

G. H. Rubæka1, K. Henriksena2, J. Petersena1, B. Rasmussena2 and S. G. Sommera1

a1 Department of Soil Science, The Danish Institute of Plant and Soil Science, Research Centre Foulum

a2 Environmental Engineering Laboratory, University of Aalborg, Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark

SUMMARY

Ammonia volatilization and denitrification were measured in a ryegrass field in Denmark after direct injection and application with trail hoses of an untreated cattle slurry and an anaerobically digested slurry in late May-early June 1993 and 1994. Ammonia volatilization was measured using a windtunnel system for a period of 8 days after slurry application. 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 harvested after slurry application. N losses through ammonia volatilization were larger in 1993 than in 1994 due to differences in climatic conditions. Ammonia volatilization was lowered substantially (47–72%), when slurry 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 were no significant differences in ammonia volatilization from the two slurry 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. Injection of the slurry gave a larger N-uptake in the first cut of grass compared to the trail-hose application. In 1993 N-uptake from the digested slurry treatment gave significantly larger N-uptake compared to the raw slurry in the first cut.

(Received May 24 1995)

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