Nitrous oxide emissions as affected by liquid and solid pig manures applied to annual and perennial forage crops on a sandy loam soil

Abstract

Emissions of nitrous oxide (N2O-N) from manure applied to annual crop (AC) and perennial forage (PF) are poorly quantified for the Canadian Prairie Region. This study used static chambers over two growing seasons to assess soil N2O-N emissions from solid pig manure (SPM) and liquid pig manure (LPM) in AC and PF systems on a sandy loam soil. In 2011, when manure application coincided with hot and wet soil conditions, both manure treatments in AC induced N2O-N emission episodes a week later. In the PF, however, only LPM resulted in an N2O-N emission peak after 8 d. In 2012, manure application did not coincide with hot and wet soil conditions, and emission rates were smaller. Overall, the effect of manure type was inconsistent. In 2011, cumulative emissions in AC from LPM and SPM were 5.8 and 7.8 kg N2O-N ha-1, respectively, and in PF were 10.7 and 0.6 kg N2O-N ha-1, respectively. In 2012, cumulative emissions were <1 kgN2O-N ha-1, except LPM in PF. In 2011, LPM had significantly higher emission factor (EF ≈ 7%) than SPM (≤0.2%) in both AC and PF, whereas in 2012 manure type had no effect on EF (≈ 0). Over the two growing seasons and across manure types, EF did not differ between AC and PF. These results suggest that SPM would reduce N2O-N emission relative to LPM when conditions favor intense denitrification.