Net Global Warming Potential of Spring Wheat Cropping Systems in a Semiarid Region

Abstract

Investigations of global warming potential (GWP) of semiarid cropping systems are needed to ascertain agriculture’s contributions to climate regulation services. This study sought to determine net GWP for three semiarid cropping systems under no-tillage management in the northern Great Plains of North America: spring wheat (Triticum aestivum L.)—fallow (SW-F), continuous spring wheat (CSW) and spring wheat—safflower (Carthamus tinctorius L.)—rye (Secale cereale L.) (SW-S-R). Management records, coupled with published carbon dioxide (CO2) emission estimates, were used to determine emissions from production inputs and field operations. Static chamber methodology was used to measure soil-atmosphere methane (CH4) and nitrous oxide (N2O) fluxes over a 3-year period and changes in profile soil organic carbon (SOC) stocks were determined over 18 years. Carbon dioxide emissions associated with production inputs and field operations were greatest for CSW, intermediate for SW-S-R and lowest for SW-F. All cropping systems were minor CH4 sinks (≤0.5 kg CH4-C ha−1 yr−1) and moderate N2O sources (1.0 to 2.8 kg N2O-N ha−1 yr−1). No differences in SOC stocks were observed among cropping systems (P = 0.78), nor did SOC stocks change significantly from baseline conditions (P = 0.82). Summing across factors, net GWP was positive for SW-F and CSW, implying net greenhouse gas (GHG) emission to the atmosphere, while net GWP for SW-S-R was negative, implying net GHG uptake. Net GWP, however, did not differ among cropping systems (P = 0.17). Management practices that concurrently improve N use efficiency and increase SOC stocks are needed for semiarid cropping systems to be net GHG sinks.

Long term agroecosystem research experimental watershed network

“…(Archer et al, 2020; Halvorson et al, 2016, 2019; Liebig et al, 2019; Liebig, Archer, & Tanaka, 2014; Nouwakpo et al, 2019; Reeves et al, 2014; Sanderson et al, 2015)…”

“…• Impacts of conservation practices on crop, forage, and livestock production and economics • Soil characteristics, greenhouse gas flux, water use • Within field water quality measured through using rainfall simulation (Archer et al, 2020;Halvorson et al, 2016Halvorson et al, , 2019Liebig et al, 2019;Nouwakpo et al, 2019;Reeves et al, 2014;Sanderson et al, 2015) Platte River/High Plains Aquifer -X 1,3,4 (Garbrecht & Starks, 2009;Moriasi et al, 2018;Schoof et al, 1987;Van Liew et al, 2003) Texas Gulf Harmel et al ( 2014) X X 1,3 4…”

Conservation practices induce tradeoffs in soil function: Observations from the northern Great Plains

“…Groups with associated soil attributes (in parentheses) were water cycling (porosity, sorptivity, and water‐holding capacity), soil structural maintenance (water stable aggregation and VESS), nutrient supply potential (soil pH, N mineralization, and cation exchange capacity), nutrient cycling potential (urease, phosphatase, and β‐glucosidase activities), biological habitat (FAME components of total biomass, bacteria, and fungi), and climate regulation (soil NO 3 –N, WFPS, and soil organic C). Metrics for climate regulation were adapted from Liebig and Varvel (2003) and were framed by previous NGPRL studies where “hot moments” of N 2 O flux occurred prior to crop seeding when soil conditions were wet and available N was abundant (Liebig et al., 2019).…”

Integrating beef cattle on cropland affects net global warming potential

“…The positive, though significantly lower net GWP for ungrazed cropland corresponded with other studies of semiarid cropping systems (116-1948 kg CO 2equiv. ha -1 yr -1 ; Liebig et al 2019;Tellez-Rio et al 2017), though a study on a similar soil type in northeast Montana found rainfed cropping systems to have negative net GWP (-292 to -2107 kg CO 2equiv. ha -1 yr -1 ; Sainju et al 2014).…”

“…Concentration of N 2 O and CH 4 inside each vial was measured by gas chromatography using a Varian Model 3800 and Combi-Pal auto-sampler. Description of the gas chromatograph, calibration protocols, and flux rate calculations are described elsewhere (Liebig et al 2019;Phillips et al 2009).…”