Spray nozzle type has a small and inconsistent effect on ammonia volatilization from surface‐applied urea ammonium‐nitrate

Abstract Ammonia (NH 3 ) volatilization reduces fertilizer use efficiency and increases environmental nitrogen (N) loss when urea ammonium‐nitrate (UAN) is surface‐applied. Volatilization is driven by localized pH increases resulting from the rapid hydrolysis of large quantities of urea. We hypothesized that nozzles that concentrate UAN in narrow bands would produce greater volatilization than nozzles that broadcast UAN widely. The effect of three nozzle types (dribble band, three‐hole streamer, and flat fan) was evaluated in field trials conducted in 2012 and 2013 in Elora, ON, Canada. UAN was surface applied at 168 kg N ha −1 (2012) or 112 kg N ha −1 (2013) onto bare soil multiple times each season. In 2013, UAN was also applied with or without a urease inhibitor (UI) as an additional treatment. Volatilization was measured for 20–34 days after UAN application using the Dosi‐Tube method. In 2012, volatilization was overall low (mean = 12.9 kg N ha −1 ), and nozzle type did not affect volatilization. In 2013, a year with greater overall volatilization even with UI use (mean = 36.3 kg N ha −1 ), flat fan nozzles reduced NH 3 volatilization relative to dribble bands by 22% ( p = 0.048). Volatilization from the three‐hole streamer nozzle was not different from either nozzle type. The magnitude of the nozzle type effect on volatilization varied across application dates in 2013, likely due to weather variation during the measurement period. The findings suggest that UAN application methods that reduce urea concentration in the soil solution can lead to modest but inconsistent reductions in volatilization.