Effects of surface manure application timing on ammonia volatilization

The purpose of this study was to evaluate the influence of timing of applic ation on ammonia (NH3) volatilization from surface-applied dairy manure. Fi eld trials were conducted over a 2-yr period (1994 and 1995) at the Agricul ture and Agri-Food Canada Research Farm in Nappan, Nova Scotia. A total of eight trials were performed in an attempt to characterize what effect the t iming of application (morning vs. late afternoon/early evening) has on NH3 volatilization losses. Ammonia losses were also related to several meteorol ogical parameters. The total percentage of NH3 volatilized in the 10 h foll owing field spreading ranged from as low as < 2% to approximately 66%. Late -day spreading typically resulted in at least a 30% reduction in overall NH 3 flux densities, primarily due to substantial reductions in NH3 losses occ urring within the first 10 h after manure application. The positive benefit s of late-day manure spreading were more pronounced during warm, dry weathe r conditions. Significant (P < 0.05) positive linear correlations were obse rved between NH3 volatilization in the 10 h following spreading and solar r adiation (r(2) = 0.56), wind speed (r(2) = 0.53), temperature (r(2) = 0.34) and vapour pressure deficit (r2 = 0.53). Results from this study have indi cated that late day manure spreading practices can substantially reduce NH3 volatilization.