Injecting dairy manure below the soil surface helped reduce ammonia emissions during recent Idaho research trials. Scientists at the USDA Agricultural Research Service Northwest Irrigation and Soils Research Laboratory in Kimberly, ID, conducted a study of four Idaho dairy farms. Liquid dairy manure, which had been stored in containment lagoons, was applied by various methods during the investigative process. Researchers compared results following three application methods, including surface broadcasting, using a rolling tine aerator to incorporate manure into the top four inches of the soil surface, or injecting 12 in. below the soil surface.

Over the three-day study period, the greatest concentration of emissions was recorded during the 48 hours immediately following the manure applications, with the majority of emissions occurring within 24 hours. Surface broadcasts resulted in average ammonia concentrations of 0.17 mg. of nitrogen per cubic meter. By comparison, shallow incorporation resulted in average ammonia emission rates of 0.16 mg. of nitrogen per cubic meter. Fields where manure had been amended using subsurface injection had average ammonia concentrations of 0.06 mg. of nitrogen per cubic meter — 65% lower than emission rates resulting from soil amendments via shallow incorporation or surface broadcast.

The research was conducted by soil scientist April Leytem and agricultural engineer David Bjorneberg. The researchers concluded dairy producers could limit losses of manure nitrogen from ammonia volatilization by immediately incorporating manure deep into the soil during application. Additional details about the research can be found at the USDA Agricultural Research Service Web site. Read more about the study online at www.ars.usda.gov/.