Effect of crop and residue type on nitrous oxide emissions from rotations in the semi-arid Canadian prairies

Crop rotations on the Canadian prairies commonly include sequences of pulses, oilseeds, and cereals; however, limited information is available regarding the influence that different crop types and sequences may have on direct nitrous oxide (N2O) emissions. A 3 yr field study was conducted on a site near Scott, SK, to compare N2O emissions from selected crop phases of rotations containing pea (Pisum sativum L.), wheat (Triticum aestivum L.), and canola (Brassica napus L.) and to examine the potential influence of these residues on N2O emissions during the subsequent crop phase. Nitrous oxide losses from N-fertilized canola or wheat crops were generally higher than losses from pea or the control treatments. Nitrous oxide losses from N-fertilized wheat or canola crops grown on pea residue were comparable or lower than losses from N-fertilized wheat or canola crops grown on wheat residues. Cumulative N2O loss over the 3 yr was significantly higher from N-fertilized wheat grown on canola compared with pea or wheat residues. Losses from wheat grown on canola residue were 67% and 56% higher than from wheat grown on pea or wheat residue, respectively. This indicates that the emission factors used to estimate direct N2O loss may need to be adjusted upwards for N-fertilized crops grown on canola compared with wheat or pea residues.