EFFECT OF SPREADING METHOD, APPLICATION RATE AND DILUTION ON AMMONIA VOLATILIZATION FROM CATTLE SLURRY

Results from a series of five small-scale plot experiments which simul ated different strategies for lowering ammonia volatilization followin g slurry application to grassland are reported. Strategies studied wer e band spreading, shallow-channel application, spike injection, rate o f surface application and dilution. Volatilization was measured over t he first 4 h following application with ventilated enclosures. Band sp read slurry resulted in 0.4 of the volatilization that occurred from s urface application of the same rate of slurry. The benefit of band spr eading was shown to arise from higher application rates in the bands w hen compared with the same quantity of slurry spread over the surface. When surface-spread slurry was applied to the same depth of slurry as in bands, the volatilization per unit volume of slurry was the same. Shallow-channel application was more effective than band spreading and lowered volatilization per unit volume of slurry to <0.1 of that from surface-spread slurry. Spike injection was equally effective as shall ow-channel application but, owing to perceived difficulties in machine design, construction and operation, was deemed impractical. Shallow-c hannel application has potential, though further work is required to o ptimize centre-to-centre spacing of the channels. As the application r ate of surface-applied raw slurry increased, ammonia volatilization pe r unit volume of slurry applied decreased. Application at 50 m3 ha-1 r esulted in 0.4 of the specific volatilization per unit volume of slurr y that occurred at 6.3 m3 ha-1. Within the dilution treatments, the am ount of water added to the slurry was linearly and inversely related t o volatilization. At a dilution of 0.9-1.2:1 water: slurry the specifi c volatilization per unit volume of slurry was 0.5 of that from undilu ted slurry.