Ammonia and nitrous oxide emissions from two acidic soils of Nova Scotia fertilised with liquid hog manure mixed with or without dicyandiamide

Gaseous nitrogen (N) loss from field-applied manure in the form of ammonia (NH3) and nitrous oxide (N2O) has negative agronomic, environmental and health implications. This study was undertaken to evaluate the combined effect of soil type and dicyandiamide (DCD) on NH3 and N2O emissions following application of liquid hog manure. Soil samples (100 g) were placed in 500 mL screw-top Mason-jars and de-ionised water was added to bring the soil samples to 50%, 70% and 90% water-filled pore space (WFPS). Slurry and slurry + DCD treatments were applied at a rate of 116 000 l ha−1. The jars were then sealed and incubated at 21 °C for 21 d. Ammonia volatilisation was quantified using boric acid traps while N2O gas concentrations were analysed using gas chromatography. Results showed that DCD had no effect (p > 0.05) on either NH3 or N2O emissions. However, soil type had a significant effect (p < 0.05) on both gases. Overall, the Pugwash soil produced 3 and 2.5 times more NH3 and N2O, respectively, than the Acadia soil. N2O emissions from both soils increased with an increase in %WFPS, indicating that during the spring and fall in Atlantic Canada, when soils are generally wet, a significant amount of N2O may be emitted from these soils. The relationship between cumulative N2O and %WFPS was best described by an exponential function R2 = 0.83 and p < 0.05 (both soils). Therefore, soil type should be taken into consideration when formulating N2O emission factors. The addition of DCD together with slurry may not be a viable strategy to mitigate N2O emissions from acidic soils. To reduce emissions of both gases, livestock slurry should not be applied on wet soils.