• Authors:
    • Euliss, N. H. Jr.
    • Laubhan, M. K.
    • Gleason, R. A.
  • Source: U.S. Geological Professional Paper 1745
  • Year: 2008
  • Summary: Chapter A: Background and Approach to Quantification of Ecosystem Services By Robert A. Gleason and Murray K. Laubhan Chapter B: Plant Community Quality and Richness By Murray K. Laubhan and Robert A. Gleason Chapter C: Carbon Sequestration By Robert A. Gleason, Brian A. Tangen, and Murray K. Laubhan Chapter D: Floodwater Storage By Robert A. Gleason and Brian A. Tangen Chapter E: Reduction of Sedimentation and Nutrient Loading By Brian A. Tangen and Robert A. Gleason Chapter F: Proposed Approach to Assess Potential Wildlife Habitat Suitability on Program Lands By Murray K. Laubhan, Kevin E. Kermes, and Robert A. Gleason
  • Authors:
    • Townsend, P. A.
    • Gray, E. M.
    • Groom, M. J.
  • Source: Conservation Biology
  • Volume: 22
  • Issue: 3
  • Year: 2008
  • Summary: Biofuels are a new priority in efforts to reduce dependence on fossil fuels; nevertheless, the rapid increase in production of biofuel feedstock may threaten biodiversity. There are general principles that should be used in developing guidelines for certifying biodiversity friendly biofuels. First, biofuel feedstocks should be grown with environmentally safe and biodiversity friendly agricultural practices. The sustainability of any biofuel feedstock depends on good growing practices and sound environmental practices throughout the fuel-production life cycle. Second, the ecological footprint of a biofuel, in terms of the land area needed to grow sufficient quantities of the feedstock, should be minimized. The best alternatives appear to be fuels of the future, especially fuels derived from microalgae. Third, biofuels that can sequester carbon or that have a negative or zero carbon balance when viewed over the entire production life cycle should be given high priority. Corn-based ethanol is the worst among the alternatives that are available at present, although this is the biofuel that is most advanced for commercial production in the United States. We urge aggressive pursuit of alternatives to corn as a biofuel feedstock. Conservation biologists can significantly broaden and deepen efforts to develop sustainable fuels by playing active roles in pursuing research on biodiversity friendly biofuel production practices and by helping define biodiversity-friendly biofuel certification standards.
  • Authors:
    • Berrada, A.
    • Reule, C. A.
    • Bartolo, M. E.
    • Halvorson, A. D.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 4
  • Year: 2008
  • Summary: Onion (Allium cepa L.) is a high cash value crop with a very shallow root system that is frequently irrigated and fertilized with high N rates to maximize yield. Converting from furrow-irrigated to drip-irrigatcd onion production may reduce N fertilizer needs, water inputs, and NO3-N leaching potential. Onion growth and N uptake, fresh yield, and residual soil NO3-N were determined under drip and furrow irrigation on a clay loam soil with N fertilizer rates from 0 to 224 kg N ha(-1). Onions were sampled bi-weekly from 25 May to 30 August in 2005 and 2006 from each treatment. In 2005, 72% less water was applied with the drip system compared with furrow system, and 57% less in 2006. Onion yields were significantly greater with the drip system. Total marketable fresh onion yield increasedwith increasing N rate in 2005 only.The drip system had more colossal and jumbo sized onions and less medium sized onions than the furrow system. Biomass production and N accumulation accelerated in mid-June each year with an average total N accumulation (leaves + bulbs) of 121 kg N ha(-1) at final harvest. Irrigation water use efficiency (IWUE) and N use efficiency (NUE) were higher with the drip system than with the furrow system. Residual soil NO3-N levels were greater in the drip-irrigated treatments after onion harvest in 2005 than in the furrow-irrigated treatments, but soil NO3-N levels were similar after harvest in 2006. Adjusted gross economic returns (less the cost of N, water, and drip system) were greater with drip irrigation than with furrow irrigation. This study demonstrates that fresh onion yields, potential economic returns, IWUE, and NUE can be improved in Colorado by using drip irrigation for onion production rather than furrow irrigation.
  • Authors:
    • Reule, C. A.
    • Del Grosso, S. J.
    • Halvorson, A. D.
  • Source: Journal of Environmental Quality
  • Volume: 37
  • Issue: 4
  • Year: 2008
  • Summary: We evaluated the effects of irrigated crop management practices on nitrous oxide (N2O) emissions from soil. Emissions were monitored from several irrigated cropping systems receiving N fertilizer rates ranging from 0 to 246 kg N ha-1 during the 2005 and 2006 growing seasons. Cropping systems included conventional-till (CT) continuous corn (Zea mays L.), no-till (NT) continuous corn, NT corn-dry bean (Phaseolus vulgaris L.) (NT-CDb), and NT corn-barley (Hordeum distichon L.) (NT-CB). In 2005, half the N was subsurface band applied as urea-ammonium nitrate (UAN) at planting to all corn plots, with the rest of the N applied surface broadcast as a polymer-coated urea (PCU) in mid-June. The entire N rate was applied as UAN at barley and dry bean planting in the NT-CB and NT-CDb plots in 2005. All plots were in corn in 2006, with PCU being applied at half the N rate at corn emergence and a second N application as dry urea in mid-June followed by irrigation, both banded on the soil surface in the corn row. Nitrous oxide fluxes were measured during the growing season using static, vented chambers (1-3 times wk-1) and a gas chromatograph analyzer. Linear increases in N2O emissions were observed with increasing N-fertilizer rate, but emission amounts varied with growing season. Growing season N2O emissions were greater from the NT-CDb system during the corn phase of the rotation than from the other cropping systems. Crop rotation and N rate had more effect than tillage system on N2O emissions. Nitrous oxide emissions from N application ranged from 0.30 to 0.75% of N applied. Spikes in N2O emissions after N fertilizer application were greater with UAN and urea than with PCU fertilizer. The PCU showed potential for reducing N2O emissions from irrigated cropping systems.
  • Authors:
    • Derner, J. D.
    • Welker, J. M.
    • Ganjegunte, G. K.
    • Vance, G. F.
    • Buyer, J. S.
    • Schuman, G. E.
    • Stahl, P. D.
    • Ingram, L. J.
  • Source: Soil Science Society of America Journal
  • Volume: 72
  • Issue: 4
  • Year: 2008
  • Summary: Good management of rangelands promotes C sequestration and reduces the likelihood of these ecosystems becoming net sources of CO2. As part of an ongoing study, soil was sampled in 2003 to investigate the long-term effects of different livestock grazing treatments on soil organic carbon (SOC), total nitrogen (TN), and microbial communities. The three treatments studied (no grazing, EX; continuously, lightly grazed [10% utilization], CL; and continuously, heavily grazed [50% utilization], CH) have been imposed on a northern mixed-grass prairie near Cheyenne, WY, for 21 yr. In the 10 yr since treatments were last sampled in 1993, the study area has been subject to several years of drought. In the 0 to 60 cm depth there was little change in SOC in the EX or CL treatments between 1993 and 2003, whereas there was a 30% loss of SOC in the CH treatment. This loss is attributed to plant community changes (from a cool-season [C-3] to a warm-season [C-4] plant dominated community) resulting in organic C accumulating nearer the soil surface, making it more vulnerable to loss. Soil TN increased in the EX and CL treatments between 1993 and 2003, but declined in the CH treatment. Differences in plant community composition and subsequent changes in SOC and TN may have contributed to microbial biomass, respiration, and N-mineralization rates generally being greatest in CL and least in the CH treatment. Although no significant differences were observed in any specific microbial group based on concentrations of phospholipid fatty acid (PLFA) biomarkers, multivariate analysis of PLFA data revealed that microbial community structure differed among treatments. The CH grazing rate during a drought period altered plant community and microbial composition which subsequently impacted biogeochemical C and N cycles.
  • Authors:
    • Hutchins, B.
    • Groover, G.
    • Stephenson, K.
    • Bosch, D. J.
  • Source: Journal of Soil and Water Conservation
  • Volume: 63
  • Issue: 2
  • Year: 2008
  • Summary: Intensive rotational grazing systems may produce multiple environmental services, including reduction of the emissions of greenhouse gases (GHG). This study investigates potential GHG emission reduction credits obtained by converting Virginia cow-calf and dairy farm operations from conventional grazing operations to rotational grazing. The quantity and value of the change in GHG emissions are estimated using new US Department of Energy guidelines. Credits are estimated under three boundary conditions and two accounting metrics. Results suggest conversion to rotational grazing can generate GHG reduction credits, but the financial benefits farms receive from emissions reductions are modest. The amount of credits received is sensitive to choice of accounting metric and boundary definition.
  • Authors:
    • Willms, W. D.
    • Ash, A. J.
    • Gillen, R. L.
    • Havstad, K. M.
    • Teague, W. R.
    • Fublendor, S. D.
    • Brown, J. R.
    • Derner, J. D.
    • Briske, D. D.
  • Source: Rangeland Ecology & Management
  • Volume: 61
  • Issue: 1
  • Year: 2008
  • Summary: In spite of overwhelming experimental evidence to the contrary, rotational grazing continues to be promoted and implemented as the only viable grazing strategy. The goals of this synthesis are to 1) reevaluate the complexity, underlying assumptions, and ecological processes of grazed ecosystems, 2) summarize plant and animal production responses to rotational and continuous grazing, 3) characterize the prevailing perceptions influencing the assessment of rotational and continuous grazing, and 4) attempt to direct the profession toward a reconciliation of perceptions advocating support for rotational grazing systems with that of the experimental evidence. The ecological relationships of grazing systems have been reasonably well resolved, at the scales investigated, and a continuation of costly grazing experiments adhering to conventional research protocols will yield little additional information. Plant production was equal or greater in continuous compared to rotational grazing in 87% (20 of 23) of the experiments. Similarly, animal production per head and per area were equal or greater in continuous compared to rotational grazing in 92% (35 of 38) and 84% (27 of 32) of the experiments, respectively. These experimental data demonstrate that a set of potentially effective grazing strategies exist, none of which have unique properties that set one apart from the other in terms of ecological effectiveness. The performance of rangeland grazing strategies are similarly constrained by several ecological variables establishing that differences among them are dependent on the effectiveness of management models, rather than the occurrence of unique ecological phenomena. Continued advocacy for rotational grazing as a superior strategy of grazing on rangelands is founded on perception and anecdotal interpretations, rather than an objective assessment of the vast experimental evidence. We recommend that these evidence-based conclusions be explicitly incorporated into management and policy decisions addressing this predominant land use on rangelands.
  • Authors:
    • Livingston, P.
    • Klonsky, K. M.
    • Munier, D. J.
    • Schmierer, J. L.
    • Brittan, K. L.
  • Source: University of California Cooperative Extension Publication
  • Year: 2008
  • Summary: Sample costs to produce field corn in the Sacramento Valley of California, USA, are presented in this study.
  • Authors:
    • Barfoot, P.
    • Brookes, G.
  • Year: 2008
  • Authors:
    • California Climate Action Registry
  • Year: 2008