Dryland Soil Management Practices Effect On Nitrogen-Use Efficiency and Nitrous Oxide Emissions.

Management practices may affect N-use efficiency and N₂O emissions under dryland cropping systems. We quantified the effects of tillage and cropping sequence combination and N fertilization on dryland soil temperature and water content at the 0- to 15-cm depth, N₂O flux, and N-use efficiency by crops in a Williams loam in eastern Montana. Treatments were no-tilled continuous malt barley (NTCB), no-tilled malt barley-pea (NTB-P), and conventional-tilled malt barley-fallow (CTB-F), each with 0 and 80 kg N ha^-1. Nitrous oxide flux was measured at 3 to 14 d intervals depending on crop growth using static, vented chambers from March to November, 2008 to 2011. Soil temperature varied but water content was greater in CTB-F than in other treatments. The N₂O flux varied with date of sampling, peaking immediately after substantial precipitation (>15 mm) and N fertilization during increased soil temperature. Total N₂O flux from March to November was greater in NTCB with 0 kg N ha^-1 or in NTB-P with 80 kg N ha^-1 than in other treatments in 2008 and 2011. Total N₂O flux was also greater in NTB-P than in NTC-B in 2011, greater with than without N fertilization from 2009 to 2011, and greater in 2011 than in other years. Nitrogen-use efficiency was greater in CTB-F with 0 kg N ha^-1 than in other treatments. Increased N supply by pea residue and N fertilization probably increased N₂O flux in NTB-P with 80 kg N ha^-1 while increased N-use efficiency reduced the flux in CTB-F with 0 kg N ha^-1 than in other treatments. For sustaining N-use efficiency by crops and reducing N₂O emissions, no-tilled barley-pea rotation without N fertilization may be adopted in dryland cropping systems in the northern Great Plains.