SUMMARYTwo field experiments commencing in winter (December) and spring (April) were conducted to determine the fate of nitrogen (N) in cattle slurry following application to grassland. In each experiment three methods of application were used: surface application, and injection ± the nitrification inhibitor, nitrapyrin. Slurry was applied at 80t ha−1, (≡248 kg total N ha−1in the winter experiment, and 262 kg N ha−1in the spring experiment). From slurry applied to the surface, total losses of N through NH3volatilization, measured using a system of wind tunnels, were 77 and 53 kg N ha−1respectively for the winter and spring experiments. Injection reduced the total NH3volatilization loss to ∼2 kg N ha−1. Following surface application, loss by denitrification, measured using an adaptation of the acetylene‐inhibition technique, was 30 and 5 kg N ha−1for the two experiments. Larger denitrification losses were observed for the injected treatments; in the winter experiment the loss from the injected slurry without nitrapyrin was 53 kgN ha−1, and with nitrapyrin 23 kgN ha−1. Total denitrification losses for the corresponding injected treatments in the spring experiment were 18 and 14 kg N ha−1. Apparent recoveries of N in grass herbage in both experiments broadly reflected the differences between treatmen