title: Long-term no-till and stover retention each decrease the global warming potential of irrigated continuous corn.
abstract: Over the last 50 years, the most increase in cultivated land area globally has been due to a doubling of irrigated land. Long-term agronomic management impacts on soil organic carbon (SOC) stocks, soil greenhouse gas (GHG) emissions, and global warming potential (GWP) in irrigated systems, however, remain relatively unknown. Here, residue and tillage management effects were quantified by measuring soil nitrous oxide (N2O) and methane (CH4) fluxes and SOC changes (ΔSOC) at a long-term, irrigated continuous corn (Zea mays L.) system in eastern Nebraska, United States. Management treatments began in 2002, and measured treatments included no or high stover removal (0 or 6.8 Mg DM ha-1yr-1, respectively) under no-till (NT) or conventional disk tillage (CT) with full irrigation (n = 4). Soil N2O and CH4fluxes were measured for five crop-years (2011-2015), and ΔSOC was determined on an equivalent mass basis to ~30 cm soil depth. Both area- and yield-scaled soil N2O emissions were greater with stover retention compared to removal and for CT compared to NT, with no interaction between stover and tillage practices. Methane comprised <1% of total emissions, with NT being CH4neutral and CT a CH4source. Surface SOC decreased with stover removal and with CT after 14 years of management. When ΔSOC, soil GHG emissions, and agronomic energy usage were used to calculate system GWP, all management systems were net GHG sources. Conservation practices (NT, stover retention) each decreased system GWP compared to conventional practices (CT, stover removal), but pairing conservation practices conferred no additional mitigation benefit. Although cropping system, management equipment/timing/history, soil type, location, weather, and the depth to which ΔSOC is measured affect the GWP outcomes of irrigated systems at large, this long-term irrigated study provides valuable empirical evidence of how management decisions can impact soil GHG emissions and surface SOC stocks.
authors.affiliation: Agroecosystem Management Research, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), University of Nebraska-Lincoln, 251 Filley Hall, Lincoln, NE, 68583-0937, USA.
authors.forename: Virginia L
authors.identifier: 0000-0003-4146-8497
authors.initials: VL
authors.lastname: Jin
authors.affiliation: Agroecosystem Management Research, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), University of Nebraska-Lincoln, 251 Filley Hall, Lincoln, NE, 68583-0937, USA.
authors.forename: Marty R
authors.initials: MR
authors.lastname: Schmer
authors.affiliation: Soil Management and Sugarbeet Research, USDA-ARS, Suite 320, 2150 Centre Avenue, Building D, Fort Collins, CO, 80526-8119, USA.
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Stewart
authors.affiliation: Agroecosystem Management Research, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), University of Nebraska-Lincoln, 251 Filley Hall, Lincoln, NE, 68583-0937, USA.|Monsanto Company, 10975 NW 121st Pl., Malcolm, NE, 68402, USA.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Sindelar
authors.affiliation: Agroecosystem Management Research, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), University of Nebraska-Lincoln, 251 Filley Hall, Lincoln, NE, 68583-0937, USA.
authors.forename: Gary E
authors.initials: GE
authors.lastname: Varvel
authors.affiliation: Agroecosystem Management Research, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), University of Nebraska-Lincoln, 251 Filley Hall, Lincoln, NE, 68583-0937, USA.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Wienhold
mesh_terms: D057914:Agricultural Irrigation; D000383:Agriculture; D018556:Crops, Agricultural; D057232:Global Warming; D017752:Greenhouse Effect; D009609:Nitrous Oxide; D012987:Soil; D003313:Zea mays / Q000254:growth & development*
chemical_list: D012987:Soil; D009609:Nitrous Oxide
keywords: conventional tillage; global warming potential; greenhouse gas intensity; methane; nitrous oxide; no-till; soil organic carbon; stover removal