Case Study: On-Farm Evaluation of Liquid Dairy Manure Application Methods to Reduce Ammonia Losses

The volatilization of NH3 from land-applied manure is not only a loss of valuable N, but also an air quality concern because NH3 plays a role in the formation of airborne particulate matter, which can be a health hazard. The relative differences in potential NH3 losses from land application of liquid dairy manure were determined via 3 methods: surface application, Aerway incorporation (shallow incorporation with a rolling tine aerator), and subsurface injection. Liquid manure was applied at a rate of 190 m3/ha on 4 farms with average N and P application rates ranging from 28 to 130 kg N/ha and 6 to 36 kg P/ha, respectively. Average NH3 concentrations were measured with passive samplers for 3 d after manure application and ranged from 0.03 to 0.21 mg NH3-N/m3 There were main effects of sampler height, day, and application method. The greatest NH3 concentrations occurred during the first 48 h after manure application. Concentrations of NH3 measured at 1 m (averaged over 48 h) indicated that surface and Aerway applications had the greatest concentrations (0.16 and 0.17 mg NH3-N/m3, respectively) whereas subsurface injection of manure resulted in a 67% decrease in NH3 concentration, which was similar to the control plots (0.06 and 0.04 mg NH3-N/m3, respectively). Subsurface injection was the best method of liquid manure application for minimizing NH3 losses.