Net Global Warming Potential and Greenhouse Gas Intensity Influenced by Irrigation, Tillage, Crop Rotation, and Nitrogen Fertilization

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 (GWPR and GHGIR) and organic C (SOC) (GWPC and GHGIC) 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, GWPR and GWPC were 160 to 9052 kg CO2 eq. ha−1 lower in irrigated and nonirrigated NTB‐P. Similarly, GHGIR and GHGIC 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.