Nitrous Oxide Emission Reduction in Cropped Fields As a Function of Timing of Liquid Manure Injection and Use of Nitrification Inhibitors.

Nitrous oxide, one of the major greenhouse gases (GHGs), is mostly derived from agriculture. About 58% of GHG emissions from agriculture are N₂O, and two‐thirds of those N₂O emissions come from cropping systems having soils that repeatedly receive manures or synthetic nitrogen fertilizers. The main objectives of this research are to investigate GHG reduction strategies and provide efficient mitigation management practices. This research compares N₂O emissions from two contrasting manure injection times (fall vs. spring), examines the effectiveness of two nitrification inhibitors {nitrapyrin and 3, 4‐dimethylpyrazole phosphate (DMPP)} and identifies the key ecological controls on N₂O flux in Alberta cropping systems. In the early fall of 2014, field experiments were initiated at two locations (Edmonton and Lacombe) and will continue until winter 2016. The two locations received different manure types; dairy manure was injected at Edmonton, while swine manure was injected at Lacombe. Flux measurements were conducted in fields and in a lab incubation on soils collected following the spring manure injection. Field flux measurements were done during the frost free periods using automated (every four hours) and manual static chambers (weekly or twice per week following major rainfall or manure injection). The incubation flux measurements were done twice a week during the first two weeks of the incubation, and once a week for the following three weeks. Based on the results from fall 2014 measurements, all manure injections resulted in a significant increase in N₂O emissions compared to the controls without manure (264 vs. 18 g N₂O‐N ha^‐1 for Edmonton, and 348 vs. 2 g N₂O‐N ha^‐1 for Lacombe; Ps < 0.005). The overall average reduction due to the use of nitrification inhibitors was about 26%. These experiments will continue during the next two growing seasons to reveal the annual effects of manure injection times and inhibitors.