The impact of management practices and meteorological conditions on ammonia and nitrous oxide emissions following application of hog slurry to forage grass in Nova Scotia

Abstract

Nitrogen (N) loss from field-applied slurry through ammonia (NH 3) volatilisation has led to the adoption of conservation strategies. While several strategies have been effective, concern is growing that some may simultaneously enhance nitrous oxide (N 2O) emissions, thus negating their overall benefits. This study evaluated the impact of slurry application rate, soil water status (dry vs. wet), simulated rainfall (irrigation), slurry dilution and meteorological conditions on NH 3 and N 2O emissions following application of hog slurry to forage grass. Increasing the slurry application rate increased NH 3 losses. Applying slurry to wet soil increased NH 3 losses on average by 8%. Simulated rainfall (irrigation) after slurry application reduced NH 3 losses by 45%, while diluting slurry decreased NH 3 emissions by 41%. Ammonia volatilisation increased with higher air and soil temperatures, net radiation, vapour pressure deficit, and evapotranspiration rates. Due to low soil NO 3 −-N contents (<5 mg kg −1 soil) caused by slow nitrification activity, all the management strategies and meteorological conditions evaluated had no effect on N 2O emissions. Therefore, NH 3 losses can be reduced without increasing N 2O losses by using proper rates, diluting slurry, applying slurry before forecasted light rainfall (∼6 mm), and most importantly applying slurry during cool days with reduced evaporative demand. Since estimated indirect N 2O emissions (i.e., emissions due to volatilised NH 3) were higher than direct emissions, more effort should be directed towards reducing NH 3 volatilisation after applying slurry to these soils.