EVALUATION OF DENITRIFICATION LOSSES BY THE ACETYLENE INHIBITION TECHNIQUE IN A PERMANENT RYEGRASS FIELD (LOLIUM-PERENNE L) FERTILIZED WITHANIMAL SLURRY OR AMMONIUM-NITRATE

In a field experiment, the effect of animal slurry, (with and without the nitrification inhibitor dicyandiamide on total denitrification los ses estimated by the C2H2 inhibition technique was measured over 2 yea rs (1989-1990). During this period, four different plots (each with fo ur replicates) were fertilized six times with 150 kg N ha-1 in the for m of cattle - pig slurry or NH4NO3. Soil samples (0-20 cm) were analys ed at regular intervals for NH4+ and NO3- concentrations. The soil wat er content was determined gravimetrically. During the first year (1989 ) total denitrification losses from unfertilized, mineral-fertilized, and animal slurry-amended plots (with or without dicyandiamide) were e stimated as 0.2, 3.1, 0.7, and 0.6 kg N ha-1, respectively. During the second year (1990) the denitrification losses were 0.4, 1.3, 0.7, and 0.7 kg N ha-1, respectively. There was a clear relationship between t he NO3- concentration or soil water content and the denitrification ra te. The results are site-und experiment-specific and cannot be general ized so far.