Investigation of soil microbial factors related to greater than expected residue induced N2O emissions from canola (Brassica napus L.)
Peer Reviewed StatusNon-Peer Reviewed
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Abstract Oilseed residues, particularly canola (Brassica napus L.), instigate higher nitrous oxide (N2O) emissions compared to pulse and wheat crop residues. We conducted an incubation experiment (84 d) using 15N and 13C labelled residues of canola, flax, pea and wheat applied at rates equivalent to those reported for crop grown in the field in Saskatchewan to assess soil biological processes related to N2O emissions. We used a combination of molecular techniques (qPCR and PLFA) to investigate the N-cycling gene abundance and microbial abundance and community structure with each of the added residues The magnitude of nitrous oxide (N2O) emission from residue amended soils were significantly higher (p<0.05) than the control treatment (without residue addition) and differed with residue type: control < Flax < pea = Wheat < canola. Residue addition significantly (p<0.05) increased denitrification gene abundances (nirS, nirK, nosZ I and nosZ II) compared to the control. However, there was no significant (p<0.05) affect on nitrification genes (archaeal and bacterial amoA). Pearson correlation of DOC and denitrification gene abundance were significant (p<0.05) across all soils. Both canola and pea residue addition resulted in a significant increase in dissolved organic C, but only canola residue resulted in decreased dissolved organic N and NO3. This suggests an interplay between biologically available C and N that differed among residue types, affecting N2O emissions. Preliminary analysis of 15N2O and 13CO2 data suggests that the stimulatory effect of canola residues on N2O emissions is due to differences in residue C.
Part OfSoils and Crops Workshop
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