Little information exists about how global warming potential (GWP) is affected by management practices in agroecosystems. We evaluated the effects of irrigation, tillage, crop rotation, and N fertilization on net GWP and greenhouse gas intensity (GHGI or GWP per unit crop yield) calculated by soil respiration (GWP(R) and GHGI(R)) and organic C (SOC) (GWP(C) and GHGI(C)) methods after accounting for CO2 emissions from all sources (irrigation, farm operations, N fertilization, and greenhouse gas [GHG] fluxes) and sinks (crop residue and SOC) in a Lihen sandy loam from 2008 to 2011 in western North Dakota. Treatments were two irrigation practices (irrigated vs. nonirrigated) and five cropping systems (conventional-till malt barley [Hordeum vulgaris L.] with N fertilizer [CTBN], conventional-till malt barley with no N fertilizer [CTBO], no-till malt barley-pea [Pisum sativum L.] with N fertilizer [NTB-P], no-till malt barley with N fertilizer, and no-till malt barley with no N fertilizer [NTBO]). While CO2 equivalents were greater with irrigation, tillage, and N fertilization than without, N2O and CH4 fluxes were 2 to 218 kg CO2 eq. ha(-1) greater in nonirrigated NTBN and irrigated CTBN than in other treatments. Previous year's crop residue and C sequestration rate were 202 to 9316 kg CO2 eq. ha(-1) greater in irrigated NTB-P than in other treatments. Compared with other treatments, GWP(R) and GWP(C) were 160 to 9052 kg CO2 eq. ha(-1) lower in irrigated and nonirrigated NTB-P. Similarly, GHGI(R) and GHGI(C) were lower in nonirrigated NTB-P than in other treatments. Regardless of irrigation practices, NTB-P may lower net GHG emissions more than other treatments in the northern Great Plains.
