,NVND Study for Greenhouse gas Reduction through Agricultural Carbon Enhancement network in Sidney, Montana Management practices, such as irrigation, tillage, cropping system, and N fertilization, may influence soil greenhouse gas (GHG) emissions. We quantified the effects of irrigation, tillage, crop rotation, and N fertilization on soil CO2, N2O, and CH4 emissions from March to November, 2008 to 2011 in a Lihen sandy loam in western North Dakota. Treatments were two irrigation practices (irrigated and non-irrigated) and five cropping systems (conventional-tilled malt barley [Hordeum vulgaris 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], and no-tilled malt barley with no N fertilizer [NTBON]). The GHG fluxes varied with date of sampling while peaking immediately after precipitation, irrigation, and/or N fertilization events during increased soil temperature. Both CO2 and N2O fluxes were greater in CTBFN under the irrigated condition but CH4 uptake was greater in NTB-PN under the non-irrigated condition than in other treatments. While tillage and N fertilization increased CO2 and N2O fluxes by 8 to 30%, N fertilization and monocropping reduced CH4 uptake by 39 to 40%. The NTB-PN, regardless of irrigation, might mitigate GHG emissions by reducing CO2 and N2O emissions and increasing CH4 uptake relative to other treatments. To account for global warming potential for such a practice, information on productions associated with CO2 emissions along with N2O and CH4 fluxes are needed.,

,High efficiency Nitrogen Study for Greenhouse gas Reduction through Agricultural Carbon Enhancement network in Fort Collins, Colorado Nitrogen fertilization is essential for optimizing crop yields; however, it increases N2O emissions. The study objective was to compare N2O emissions resulting from application of commercially available enhanced-efficiency N fertilizers with emissions from conventional dry granular urea in irrigated cropping systems. These emissions were monitored from several irrigated cropping systems receiving N fertilizer rates ranging from 0-202 kg/ha years 2009-2011. Fertilizer types include Urea, UAN, SuperU (N inhibitor), ESN(slow release). In 2009, we eliminated the conventional tillage treatment. Cropping systems from 2009-2011 included a more conservative strip-till continuous corn (ST-CC) rotation and a no-till continuous corn (NT-CC) rotation. We also tested different fertilizer placements, including broadcast (bc), surface banded (bd) sub-surface banded (ssb) N inputs. Nitrous oxide fluxes were measured during these three growing seasons using static, vented chambers and a gas chromatograph analyzer. This work shows that the use of no-till and enhanced-efficiency N fertilizers can potentially reduce N2O emissions from irrigated systems.,

,Information is needed to mitigate dryland soil greenhouse gas (GHG) emissions by using novel management practices. We evaluated the effects of cropping sequence and N fertilization on dryland soil temperature and water content at the 0- to 15-cm depth and surface CO2, N2O, and CH4 fluxes in a Williams loam in eastern Montana. Treatments were no-tilled continuous malt barley (Hordeum vulgaris L.) (NTCB), no-tilled malt barley-pea (Pisum sativum L.) (NTB-P), and conventional-tilled malt barley-fallow (CTB-F) (control), each with 0 and 80 kg N ha-1. Gas fluxes were measured at 3 to 14 d intervals using static, vented chambers from March to November, 2008 to 2011. Soil temperature varied but water content was greater in CTB-F than in other treatments. The GHG fluxes varied with date of sampling, peaking immediately after substantial precipitation (>15 mm) and N fertilization during increased soil temperature. Total CO2 flux from March to November was greater in NTCB and NTB-P with 80 kg N ha-1 than in other treatments from 2008 to 2010. Total N2O flux was greater in NTCB with 0 kg N ha-1 and in NTB-P with 80 kg N ha-1 than in other treatments in 2008 and 2011. Total CH4 uptake was greater with 80 than with 0 kg N ha-1 in NTCB in 2009 and 2011. Because of intermediate level of CO2 equivalent of GHG emissions and known favorable effect on malt barley yield, NTB-P with 0 kg N ha-1 might mitigate GHG emissions and sustain crop yields compared to other treatments in eastern Montana. For accounting global warming potential of management practices, however, additional information on soil C dynamics and CO2 associated with production inputs and machinery use are needed.,,

,ACRE Study for Greenhouse gas Reduction through Agricultural Carbon Enhancement network in West Lafayette, Indiana In-field measurements of direct soil greenhouse gas (GHG) emissions provide critical data for quantifying the net energy efficiency and economic feasibility of crop residue based bioenergy production systems. A major challenge to such assessments has been the paucity of field studies addressing the effects of crop residue removal and associated best practices for soil management (i.e., conservation tillage) on soil emissions of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). This regional survey summarizes soil GHG emissions from nine maize production systems evaluating different levels of corn stover removal under conventional or conservation tillage management across the US Corn Belt. Cumulative growing season soil emissions of CO2, N2O, and/ or CH4 were measured for 2–5 years (2008–2012) at these various sites using a standardized static vented chamber technique as part of the USDA-ARS’s Resilient Economic Agricultural Practices (REAP) regional partnership. Cumulative soil GHG emissions during the growing season varied widely across sites, by management, and by year. Overall, corn stover removal decreased soil total CO2 and N2O emissions by -4 and -7 %, respectively, relative to no removal. No management treatments affected soil CH4 fluxes.When aggregated to total GHG emissions (Mg CO2eq ha-1) across all sites and years, corn stover removal decreased growing season soil emissions by -5±1 % (mean±se) and ranged from -36 % to 54 % (n=50). Lower GHG emissions in stover removal treatments were attributed to decreased C and N inputs into soils, as well as possible microclimatic differences associated with changes in soil cover. High levels of spatial and temporal variabilities in direct GHG emissions highlighted the importance of site-specific management and environmental conditions on the dynamics of GHG emissions from agricultural soils.,

,Nitrogen Source Study for Greenhouse gas Reduction through Agricultural Carbon Enhancement network in Fort Collins, Colorado Nitrogen fertilization is essential for optimizing crop yields; however, it increases N2O emissions. The study objective was to compare N2O emissions resulting from application of commercially available enhanced-effi ciency N fertilizers with emissions from conventional dry granular urea in irrigated cropping systems. These emissions were monitored from several irrigated cropping systems receiving N fertilizer rates ranging from 0-246 kg/ha from years 2007-2008 with intermediate rates of 157 kg/ha applied to the barley crop in corn-barley rotation and 56 kg/ha applied to the dry bens in the corn-dry bean rotation. Cropping systems included conventional-till continuous corn (CT-CC), no-till continuous corn (NT-CC), no-till corn–dry bean (NT-CDb), and no-till corn–barley (NT-CB). Nitrous oxide fluxes were measured during ten growing seasons using static, vented chambers and a gas chromatograph analyzer. This work shows that the use of no-till and enhanced-effi ciency N fertilizers can potentially reduce N2O emissions from irrigated systems.,

,Nitrogen Source Study for Greenhouse gas Reduction through Agricultural Carbon Enhancement network in Fort Collins, Colorado Nitrogen fertilization is essential for optimizing crop yields; however, it increases N2O emissions. The study objective was to compare N2O emissions resulting from application of commercially available enhanced-effi ciency N fertilizers with emissions from conventional dry granular urea in irrigated cropping systems. These emissions were monitored from several irrigated cropping systems receiving N fertilizer rates ranging from 0-246 kg/ha from years 2007-2008 with intermediate rates of 157 kg/ha applied to the barley crop in corn-barley rotation and 56 kg/ha applied to the dry bens in the corn-dry bean rotation. Cropping systems included conventional-till continuous corn (CT-CC), no-till continuous corn (NT-CC), no-till corn–dry bean (NT-CDb), and no-till corn–barley (NT-CB). Nitrous oxide fluxes were measured during ten growing seasons using static, vented chambers and a gas chromatograph analyzer. This work shows that the use of no-till and enhanced-effi ciency N fertilizers can potentially reduce N2O emissions from irrigated systems.,

,Shortgrass Steppe for Greenhouse gas Reduction through Agricultural Carbon Enhancement network in Nunn, Colorado Cattle play a major role in nutrient cycling of grassland ecosystems through biomass removal and excrement deposition (urine and feces). We studied the effects of cattle excrement patches (urine at 430 and feces at 940 kg N ha-1) on nitrous oxide (N2O) and methane (CH4) fluxes using semi-static chambers on cool-season (C3), Bozoisky-select (*Psathyrostachys juncea*) pasture, and warm-season (C4)-dominated native rangeland of the shortgrass steppe (SGS) in northeastern Colorado. Nitrous oxide emission factors (EF; i.e., percent of added N emitted as N2O-N) did not differ between urine and feces on the C4-dominated native rangeland (0.11 and 0.10%) and C3 pasture (0.13 and 0.10%). These EFs are substantially less than the Intergovernmental Panel on Climate Change (IPCC) Tier 1 Default EF (2%) for manure deposited on pasture, indicating that during dry years the IPCC Tier 1 Default EF would result in a significant overestimation of emissions from excrement patches deposited on SGS C4-dominated native rangeland and C3 pasture. Over the first year of the study (19 June 2012 to 18 June 2013), cumulative CH4 uptake was 38% greater for urine (-1.49 vs. -1.08 kg CH4-C ha-1) and 28% greater for control plots (-2.09 vs. -1.63 kg CH4-C ha-1) on C4-dominated native rangeland compared to C3 pasture. In contrast, feces patches were net sources of CH4 with emissions from the C3 pasture (0.64 kg CH4-C ha-1) 113% greater than the C4-dominated native rangeland (0.30 kg CH4-C ha-1). Conversion of C4-dominated native rangeland to C3 pasture can have short and long term effects on CH4 uptake; therefore consideration should be taken before implementing this management practice.,

,NWISRL South Farm Study for Greenhouse gas Reduction through Agricultural Carbon Enhancement network in Kimberly, Idaho We report N2O emissions along with CO2 and CH4 from a silage corn (2013)–barley (2014)–alfalfa (2015) rotation under conventional tillage and sprinkler irrigation. The main study objectives were to evaluate the effectiveness of an enhanced-efficiency fertilizer (SuperU; stabilized granular urea with urease and nitrification inhibitors) to reduce N2O emissions when compared to granular urea, and determine GHG emissions from fall-applied dairy manure or composted dairy manure and spring-applied dairy manure. Nitrogen treatments were only applied during the first two years of the study. Compared to urea, SuperU plots emitted 53% less N2O during the monitoring period with corn, while no N2O emission reductions occurred in 2014 with barley. The N2O-N emission losses as a percentage of total N applied were 0.21% and 0.04% for urea and SuperU in 2013, respectively, with losses of 0.05% from both urea fertilizers in 2014. On average, N2O fluxes from fall and spring manure were statistically similar and greater than the other N treatments in 2014, and there was a lasting manure treatment effect on emissions when under alfalfa. Carbon dioxide fluxes, on average, were greatest from fall- and spring-applied manure during the first two years of study. Methane fluxes were negative on average, indicating microbial oxidation, and no differences occurred among the N treatments. Silage corn, barley grain, and alfalfa yields were statistically similar among all N treatments. This work demonstrates that SuperU can potentially reduce N2O emissions from irrigated cropping systems in the semiarid western United States while not affecting crop yields.,

,Nitrogen Rate Study for Greenhouse gas Reduction through Agricultural Carbon Enhancement network in Fort Collins, Colorado Nitrogen fertilization is essential for optimizing crop yields; however, it increases N2O emissions. These emissions were monitored from several irrigated cropping systems receiving N fertilizer rates ranging from 0-246 kg/ha from years 2002-2006. Cropping systems included conventional-till continuous corn and no-till continuous corn at varying N rates. Nitrous oxide fluxes were measured during four growing seasons using static, vented chambers and a gas chromatograph analyzer. This work shows that the use of no-till can potentially reduce N2O emissions from irrigated systems and increase soil carbon storage.,

,WQFS Study for Greenhouse gas Reduction through Agricultural Carbon Enhancement network in West Lafayette, Indiana Relative contributions of diverse, managed ecosystems to greenhouse gases are not completely documented. This study was conducted to estimate soil surface fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2 O) as affected by management practices and weather. Gas fluxes were measured by vented, static chambers in Drummer and Raub soil series during two growing seasons. Treatments evaluated were corn cropped continuously (CC) or in rotation with soybean (CS) and fertilized with in-season urea-ammonium nitrate (UAN) or liquid swine manure applied in the spring or fall. Soybean (SC) rotated with CS and restored prairie grass (RP) were also included. The CO2 fluxes correlated (P≤0.001) with soil temperature (ρ: 0.74) and accumulated rainfall 120 h before sampling (ρ: 0.53); N2O fluxes correlated with soil temperature (ρ: 0.34). Seasonal CO2–C emissions were not different across treatments (4.4 Mg ha−1 yr−1) but differed between years. Manured soils were net seasonal CH4–C emitters (0.159–0.329 kg ha−1 yr−1), whereas CSUAN and CCUAN Treatments significantly influenced seasonal N2O–N emissions (P< 0.001) and ranged from <1.0 kg ha−1yr−1in RP and SC to between 3 and 5 kg ha−1yr−1in CC (fall application) and CSUAN and >8 kg ha−1yr−1in CC (spring application); differences were driven by pulse emissions after N fertilization in concurrence with major rainfall events. These results suggest fall manure application, corn–soybean rotation, and restoration of prairies may diminish N2O emissions and hence contribute to global warming mitigation.,