Tillage and N source influence soil-emitted nitrous oxide in the Alberta Parkland region

Zero tillage systems are receiving attention as possible strategies for seq uestering atmospheric carbon. This benefit may be offset by increased N2O e missions, which have been reported for soils under zero tillage (ZT) compar ed to those under more intensive tillage (IT). Comparisons of N2O emissions from the two systems have been restricted to the growing season, but subst antial losses of N2O have been reported during spring thaw events in many r egions. Inorganic and organic additions of nitrogen and fallowing have a: s o been shown to increase levels of soil-emitted N2O. The objectives for thi s study were: (i) to confirm that losses of N2O are higher under ZT than un der IT in Alberta Parkland agroecosystems; (ii) to compare the relative inf luence of urea fertilizer (56 or 100 kg N ha(-1)), field pea residue (dry m atter at 5 Mg ha(-1)), sheep manure (dry matter at 40 Mg ha(-1)) additions, and fallow on total N2O losses; and (iii) to investigate possible interact ions between fertility and tillage treatments. Gas samples were collected u sing vented soil covers at three sites near Edmonton, Alberta during 1993, 1994, and 1995. Gas samples were analyzed using a gas chromatograph equippe d with a Ni-63; electron capture detector. Estimated annual N2O loss ranged from 0.1 to 4.0 kg N ha(-1). Emissions during summer were slightly higher, similar, or lower on ZT compared to those under IT, but were consistently lower on ZT plots during spring thaw. Combined estimates (spring plus summe r) of N2O loss under ZT were equal to or lower than those under IT. Highest overall losses were observed on fallow plots, followed by fertilizer, pea residue, and then either manure or control plots. We conclude that ZT manag ement systems have potential for reducing agricultural greenhouse gas emiss ions in the Alberta Parkland region.