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Land use and management practices may influence plant C inputs and soil CO2 emission. We evaluated the effect of a combination of irrigation, tillage, cropping system, and N fertilization on plant biomass C, soil temperature and water content at the 0- to 15-cm depth, and CO2 emission in a sandy loam soil from April to October, 2006 to 2008, in western North Dakota. Treatments were two irrigation practices (irrigated and unirrigated) and six cropping systems (conventional-tilled malt barley [Hordeum vulgare L.] with N fertilizer [CTBFN], conventional-tilled malt barley with no N fertilizer [CTBON], no-tilled malt barley–pea [Pisum sativum L.] with N fertilizer [NTB-PN], no-tilled malt barley with N fertilizer [NTBFN], no-tilled malt barley with no N fertilizer [NTBON], and no-tilled Conservation Reserve Program [NTCRP]). Plant biomass C was greater in NTBFN than in NTBON in 2006 and 2007 but was greater in NTB-PN than in CTBON, NTBON, or NTCRP in 2008. Soil temperature was greater but water content was lower in NTCRP than in CTBFN and NTBFN. Soil CO2 flux peaked immediately following heavy rain or irrigation (>15 mm). Total CO2 flux from April to October was greater in the irrigated than in the unirrigated practice and greater in NTCRP than in annual cropping systems. Soil CO2 emission was probably related more to soil temperature and water content or tillage than to aboveground plant C input. Because of reduced CO2 flux compared with CTBON and NTCRP but similar biomass yield as NTBFN and CTBFN, NTB-PN may be used to reduce CO2 emission from croplands in the northern Great Plains.
