Losses of nitrogen by denitrification from a grassland soil fertilized with cattle slurry and calcium nitrate

Losses of N by denitrification from an imperfectly drained grassland soil were measured by the acetylene-inhibition technique over a 1-yr period, during which applications of up to 200 kg ha ^?1 of N as cattle slurry or calcium nitrate were made. The quantities of N lost from nitrate-treated soil were much greater than from slurry-treated areas, and ranged up to 21% of the N applied. The losses occurred predominantly over brief periods following fertilizer application in the spring. Ratios of N released as N₂ to that released as N₂O increased as denitrification rates increased. The highest ratio recorded, 24, may have been a conservative estimate because inhibition of N₂O reduction may not have been complete on all occasions. Increased respiration was observed in the soil profile as a result of adding C₂H₂. This effect should be taken into account in interpreting experiments using the C₂H₂-inhibition technique.