• Authors:
    • Pennock,D. J.
    • Farrell,R.
    • Desjardins,R. L.
    • Pattey,E.
    • MacPherson,J. I.
  • Source: Canadian Journal of Soil Science
  • Volume: 85
  • Issue: 1
  • Year: 2005
  • Summary: One impediment to accurate national estimation of N2O is the difficulty in upscaling N2O measurements made at discrete points to larger field and regional scales. Our objective was to estimate N2O emissions during snowmelt in 2002 for a township (approximately 92 km2) near Laird, Saskatchewan. Chamber measurements were made at 12 sites in the township: four fields with canola (Brassica napus L.) residues, four with pea (Pisum sativum L.) residues, three with wheat (Triticum aestivum L.) residues, and one field that received cattle manure. Ten sampling chambers were used at each site, and N2O samples were made on 7 d during the snowmelt period (from 2002 Apr. 03 to Apr. 17). Cumulative N2O emissions during the 14 days of the snowmelt period differed between crop residue types: cumulative emissions from sites with wheat residues were 105.6 g N2O-N ha-1 and were significantly higher (P < 0.1) than those from fields with pea and canola residues (79.6 and 75.2 g N2O-N ha-1 respectively). The single manured site assessed had the highest cumulative emissions of 330.7 g N2O-N ha-1. The crop-specific emissions from the chamber-based measurements were multiplied by the area of each crop type in the township to calculate an area-weighted value for emissions. Cumulative emissions were 93.4 g N2O-N ha-1 for the chamber-based measurements. Water-filled pore space and soil temperature were not significantly correlated with cumulative emissions. Cumulative emissions from sites with fall nitrate levels below 8.0 kg ha-1 were consistently lower than those above this threshold. The emissions for the Laird township were well below the emissions calculated for most other studies in the Prairies and in central Canada. The lower emissions were probably due to low soil water contents and soil nitrate levels in the fall of 2001 and below normal snowfall in the winter of 2001–2002. This reinforces the importance in antecedent moisture conditions and soil N levels for modeling of emissions at snowmelt.
  • Authors:
    • Powers, S.
  • Source: Technical Report NREL/TP-510-37500
  • Year: 2005
  • Summary: Corn, soybeans and corn stover are all valuable feedstocks for conversion of biomass into consumer goods. Utilizing these agricultural products and residues creates a potential for both environmental benefits and deleterious impacts. The national use of these products could have a disproportionate negative impact in the Midwestern states on the soil and water resources, while having positive impacts on air quality and global climate change over a wider geographic scale. Many studies completed to date that have quantified the environmental impacts of bio-based products have focused on the air quality and greenhouse gas (GHG) benefits (Wang, 1999; Sheehan et al., 2002 Heller et al., 2003). There are clear benefits to using bio-based materials, especially in terms of greenhouse gas generation. Plant growth consumes atmospheric carbon dioxide is transformed to plant matter. Eventually, the carbon is released back to the environment at the end-of-life stage of a bio-based product or fuel. However, that release results in a near zero net GHG emission. In comparison, combustion of fossil fuels cause carbon sequestered in the subsurface for millennia to be added to our atmospheric carbon dioxide load.
  • Authors:
    • Abrahamson, L. P.
    • White, E. H.
    • Cameron, K. C.
    • Phillips, I. S.
    • Kopp, R. F.
    • Lin, J.
    • Volk, T. A.
    • Smart, L. B.
  • Source: Unasylva
  • Volume: 221
  • Issue: 56
  • Year: 2005
  • Summary: A willow breeding programme focuses on improving growth, optimizing relevant traits and lowering production costs to ensure the long-term viability of willow crop systems for producing energy, restoring degraded sites and improving water quality.
  • Authors:
    • O'Neil, K.
    • Nyiraneza ,J.
    • Leep, R.
    • Black, J. R.
    • Mutch, D.
    • Labarta, R.
    • Swinton, S. M.
    • Snapp, S. S.
  • Source: Agronomy Journal
  • Volume: 97
  • Issue: 1
  • Year: 2005
  • Summary: The integration of cover crops into cropping systems brings costs and benefits, both internal and external to the farm. Benefits include promoting pest-suppression, soil and water quality, nutrient cycling efficiency, and cash crop productivity. Costs of adopting cover crops include increased direct costs, potentially reduced income if cover crops interfere with other attractive crops, slow soil warming, difficulties in predicting N mineralization, and production expenses. Cover crop benefits tend to be higher in irrigated systems. The literature is reviewed here along with Michigan farmer experience to evaluate promising cover crop species for four niches.
  • Authors:
    • Spokas, K. A.
    • Burger, M.
    • Venterea, R. T.
  • Source: Journal of Environmental Quality
  • Volume: 34
  • Issue: 5
  • Year: 2005
  • Summary: Comprehensive assessment of the total greenhouse gas (GHG) budget of reduced tillage agricultural systems must consider emissions of nitrous oxide (N2O) and methane (CH4), each of which have higher global warming potentials than carbon dioxide (CO2). Tillage intensity may also impact nitric oxide (NO) emissions, which can have various environmental and agronomic impacts. In 2003 and 2004, we used chambers to measure N2O, CH4, and NO fluxes from plots that had been managed under differing tillage intensity since 1991. The effect of tillage on non-CO2 GHG emissions varied, in both magnitude and direction, depending on fertilizer practices. Emissions of N2O following broadcast urea (BU) application were higher under no till (NT) and conservation tillage (CsT) compared to conventional tillage (CT). In contrast, following anhydrous ammonia (AA) injection, N2O emissions were higher under CT and CsT compared to NT. Emissions following surface urea ammonium nitrate (UAN) application did not vary with tillage. Total growing season non-CO2 GHG emissions were equivalent to CO2 emissions of 0.15 to 1.9 Mg CO2 ha-1 yr-1 or 0.04 to 0.53 Mg soil-C ha-1 yr-1. Emissions of N2O from AA-amended plots were two to four times greater than UAN- and BU-amended plots. Total NO + N2O losses in the UAN treatment were approximately 50% lower than AA and BU. This study demonstrates that N2O emissions can represent a substantial component of the total GHG budget of reduced tillage systems, and that interactions between fertilizer and tillage practices can be important in controlling non-CO2 GHG emissions.
  • Authors:
    • Dell, C. J.
    • Venterea, R. T.
    • Sauer, T. J.
    • Allmaras, R. R.
    • Reicosky, D. C.
    • Johnson, J. M. F
  • Source: Soil & Tillage Research
  • Volume: 83
  • Issue: 1
  • Year: 2005
  • Summary: The central USA contains some of the most productive agricultural land of the world. Due to the high proportion of land area committed to crops and pasture in this region, the carbon (C) stored and greenhouse gas (GHG) emission due to agriculture represent a large percentage of the total for the USA. Our objective was to summarize potential soil organic C (SOC) sequestration and GHG emission from this region and identify how tillage and cropping system interact to modify these processes. Conservation tillage (CST), including no-tillage (NT), has become more widespread in the region abating erosion and loss of organic rich topsoil and sequestering SOC. The rate of SOC storage in NT compared to conventional tillage (CT) has been significant, but variable, averaging 0.40 ± 0.61 Mg C ha-1 year-1 (44 treatment pairs). Conversion of previous cropland to grass with the conservation reserve program increased SOC sequestration by 0.56 ± 0.60 Mg C ha-1 year-1 (five treatment pairs). The relatively few data on GHG emission from cropland and managed grazing land in the central USA suggests a need for more research to better understand the interactions of tillage, cropping system and fertilization on SOC sequestration and GHG emission.
  • Authors:
    • Frank, A. B.
    • Hanson, J. D.
    • Johnson, H. A.
    • Liebig, M. A.
  • Source: Biomass & Bioenergy
  • Volume: 28
  • Issue: 4
  • Year: 2005
  • Summary: Switchgrass (Panicum virgatum L.) is considered to be a valuable bioenergy crop with significant potential to sequester soil organic carbon (SOC). A study was conducted to evaluate soil carbon stocks within established switchgrass stands and nearby cultivated cropland on farms throughout the northern Great Plains and northern Cornbelt. Soil from 42 paired switchgrass/cropland sites throughout MN, ND, and SD was sampled to a depth of 120 cm and analyzed for soil carbon in depth increments of 0-5, 5-10, 10-20, 20-30, 30-60, 60-90, and 90-120 cm. SOC was greater (P < 0.1) in switchgrass stands than cultivated cropland at 0-5, 30-60, and 60-90 cm. Differences in SOC between switchgrass stands and cultivated cropland were especially pronounced at deeper soil depths, where treatment differences were 7.74 and 4.35 Mg ha(-1) for the 30-60 and 60-90 cm depths, respectively. Greater root biomass below 30 cm in switchgrass likely contributed to trends in SOC between switchgrass stands and cultivated cropland. Switchgrass appears to be effective at storing SOC not just near the soil surface, but also at depths below 30 cm where carbon is less susceptible to mineralization and loss. Published by Elsevier Ltd.
  • Authors:
    • Schuman, G. E.
    • Gollany, H. T.
    • Ellert, B. H.
    • Reeder, J. D.
    • Morgan, J. A.
    • Liebig, M. A.
  • Source: Soil & Tillage Research
  • Volume: 83
  • Issue: 1
  • Year: 2005
  • Summary: Concern over human impact on the global environment has generated increased interest in quantifying agricultural contributions to greenhouse gas fluxes. As part of a research effort called GRACEnet (Greenhouse Gas Reduction through Agricultural Carbon Enhancement Network), this paper summarizes available information concerning management effects on soil organic carbon (SOC) and carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) fluxes in cropland and rangeland in northwestern USA and western Canada, a region characterized by its inherently productive soils and highly variable climate. Continuous cropping under no-tillage in the region increased SOC by 0.27 ± 0.19 Mg C ha-1 yr-1, which is similar to the Intergovernmental Panel on Climate Change (IPCC) estimate for net annual change in C stocks from improved cropland management. Soil organic C sequestration potential for rangelands was highly variable due to the diversity of plant communities, soils, and landscapes, underscoring the need for additional long-term C cycling research on rangeland. Despite high variability, grazing increased SOC by 0.16 ± 0.12 Mg C ha-1 yr-1 and converting cropland or reclaimed mineland to grass increased SOC by 0.94 ± 0.86 Mg C ha-1 yr-1. Although there was generally poor geographical coverage throughout the region with respect to estimates of N2O and CH4 flux, emission of N2O was greatest in irrigated cropland, followed by non-irrigated cropland, and rangeland. Rangeland and non-irrigated cropland appeared to be a sink for atmospheric CH4, but the size of this sink was difficult to determine given the few studies conducted. Researchers in the region are challenged to fill the large voids of knowledge regarding CO2, N2O, and CH4 flux from cropland and rangeland in the northwestern USA and western Canada, as well as integrate such data to determine the net effect of agricultural management on radiative forcing of the atmosphere.
  • Authors:
    • Martin, R. C.
    • Patterson, G.
    • Fredeen, A.
    • Cohen, R. D. H.
    • Lynch, D. H.
  • Source: Canadian Journal of Soil Science
  • Volume: 85
  • Issue: 2
  • Year: 2005
  • Summary: The GrassGro model (a computer simulation of management-induced changes in range and pasture forage and livestock productivity) was combined with spreadsheet analyses to estimate the influence of improved grazing practices on soil organic carbon (SOC), and farm profitability, across native rangelands and tame pastures of the southern Canadian Prairies. Improved practices included complementary grazing (CG) and reduced stocking density (RSD) on rangeland; and N fertilization (FERT), seeded grass/legumes grazed continuously (GLGC) or rotationally (GLGR), and RSD on tame pastures. The analysis was stratified into three ecoregions on the basis of similarities in climate and soil type. Averaged over 30 yr and ecoregions, SOC rates of gain through improved management were 5 (RSD) to 26 (CG) kg C ha(-1) yr(-1) for rangelands, and 86 (RSD), 75 (GLGC), 62 (GLGR) and 222 (FERT) kg C ha(-1) yr(-1) for tame pastures. Gains with FERT were considered largely negated by associated energy (C) costs, N2O emissions, and shifts in grassland species. The CG system alone improved net returns to the producer. The estimated potential combined SOC gain on prairie grazinglands (11.5 Mha) was 1.63 MMT CO2 yr(-1) (or 0.465 MMT C yr(-1)), slightly less than the 1.70 MMT CO2 yr(-1) currently emitted from agricultural soils in Canada.
  • Authors:
    • Johnson, D. W.
    • Moeltner, K.
    • van Kooten, G. C.
    • Manley, J.
  • Source: Climatic Change
  • Volume: 68
  • Issue: 1-2
  • Year: 2005
  • Summary: Carbon terrestrial sinks are often seen as a low-cost alternative to fuel switching and reduced fossil fuel use for lowering atmospheric CO2. To determine whether this is true for agriculture, one meta-regression analysis (52 studies, 536 observations) examines the costs of switching from conventional tillage to no-till, while another (51 studies, 374 observations) compares carbon accumulation under the two practices. Costs per ton of carbon uptake are determined by combining the two results. The viability of agricultural carbon sinks is found to vary by region and crop, with no-till representing a low-cost option in some regions (costs of less than $10 per tC), but a high-cost option in others (costs of $100-$400 per tC). A particularly important finding is that no-till cultivation may store no carbon at all if measurements are taken at sufficient depth. In some circumstances no-till cultivation may yield a triple dividend of carbon storage, increased returns and reduced soil erosion, but in many others creating carbon offset credits in agricultural soils is not cost effective because reduced tillage practices store little or no carbon.