• Authors:
    • Rykiel, E. J. Jr.
    • Vaughan, B. E.
    • Oliveira, M. E. D. D.
  • Source: BioScience
  • Volume: 55
  • Issue: 7
  • Year: 2005
  • Summary: The major contributor to global warming is considered to be the high levels of greenhouse gas emissions, especially carbon dioxide (CO2), caused by the burning of fossil fuel. Thus, to mitigate CO2 emissions, renewable energy sources such as ethanol have been seen as a promising alternative to fossil fuel consumption. Brazil was the world's first nation to run a large-scale program for using ethanol as fuel. Eventually, the United States also developed large-scale production of ethanol. In this study, we compare the benefits and environmental impacts of ethanol fuel, in Brazil and in the United States, using the ecological footprint tool developed by Wackernagel and Rees. We applied the STELLA model to gauge possible outcomes as a function of variations in the ethanol production scenario.
  • Authors:
    • Paustian,Keith
    • Cole,C. Vernon
    • Sauerbeck,Dieter
    • Sampson,Neil
    • Peairs,F. B.
    • Bean,B.
    • Gossen,B. D.
  • Source: Agronomy Journal
  • Volume: 97
  • Issue: 2
  • Year: 2005
  • Summary: The intensification of traditional wheat (Triticum aestivum L.)-fallow production systems may have important consequences for management of insects, pathogens, and weeds in Great Plains dryland production systems. Assessment of these consequences is difficult due to the diversity of production systems, environmental conditions, and pests found in the region. Certain pest groups, such as weeds, traditionally controlled during the fallow period, may be favored by intensified cropping while others, such as those specializing on wheat, should be disadvantaged. Changes in pest and disease complexes will likely be evolutionary rather than revolutionary, as has been the case with other significant changes in production practices. Preventive practices in dryland production systems currently emphasize the control of grassy weeds while intensified systems may have less emphasis on the control of volunteer wheat. Crop rotation will remain a key avoidance strategy for pathogens and will help broaden herbicide options. Pest monitoring provides essential information on pest activity and environmental conditions and will become more complex as production systems are intensified. Important suppressive practices for dryland production systems include conservation biological control, tillage, and chemical controls. Chemical control, in particular, is expected to become more complicated due to drift concerns, rotational restrictions, the possible need for herbicide-tolerant crops, and the development of weed populations resistant to glyphosate. Pest management requirements should be considered during cropping system design and establishment.
  • Authors:
    • Erbach, D. C.
    • Stokes, B. J.
    • Graham, R. L.
    • Turhollow, A. F.
    • Wright, L. L.
    • Perlack, R. D.
  • Year: 2005
  • Authors:
    • Patzek, T. W.
    • Pimentel, D.
  • Source: Natural Resources Research
  • Volume: 14
  • Issue: 1
  • Year: 2005
  • Summary: Energy outputs from ethanol produced using corn, switchgrass, and wood biomass were each less than the respective fossil energy inputs. The same was true for producing biodiesel using soybeans and sunflower, however, the energy cost for producing soybean biodiesel was only slightly negative compared with ethanol production. Findings in terms of energy outputs compared with the energy inputs were: * Ethanol production using corn grain required 29% more fossil energy than the ethanol fuel produced. * Ethanol production using switchgrass required 50% more fossil energy than the ethanol fuel produced. * Ethanol production using wood biomass required 57% more fossil energy than the ethanol fuel produced. * Biodiesel production using soybean required 27% more fossil energy than the biodiesel fuel produced (Note, the energy yield from soy oil per hectare is far lower than the ethanol yield from corn). * Biodiesel production using sunflower required 118% more fossil energy than the biodiesel fuel produced.
  • Authors:
    • Seidel, R.
    • Douds, D.
    • Hanson, J.
    • Hepperly, P.
    • Pimentel, D.
  • Source: BioScience
  • Volume: 55
  • Issue: 7
  • Year: 2005
  • Summary: Various organic technologies have been utilized for about 6000 years to make agriculture sustainable while conserving soil, water, energy, and biological resources. Among the benefits of organic technologies are higher soil organic matter and nitrogen, lower fossil energy inputs, yields similar to those of conventional systems, and conservation of soil moisture and water resources (especially advantageous under drought conditions). Conventional agriculture can be made more sustainable and ecologically sound by adopting some traditional organic farming technologies.
  • 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:
    • Lal, R.
    • Puget, P.
  • Source: Soil & Tillage Research
  • Volume: 80
  • Issue: 1-2
  • Year: 2005
  • Summary: Minimum tillage practices are known for increasing soil organic carbon (SOC). However, not all environmental situations may manifest this potential change. The SOC and N stocks were assessed on a Mollisol in central Ohio in an 8-year-old tillage experiment as well as under two relatively undisturbed land uses; a secondary forest and a pasture, on the same soil type. Cropped systems had 51 +/- 4 (equiv. mass) Mg ha(-1) lower SOC and lower 3.5 +/- 0.3 (equiv. mass)Mg ha(-1) N in the top 30cm soil layer than Linder forest. Being a secondary forest, the loss in SOC and N stocks by cultivation may have been even more than these reported herein. No differences among systems were detected below this depth. The SOC stock in the pasture treatment was 29 +/- 3 Mg ha(-1), greater in the top 10 cm layer than in cultivated soils. but was similar to those tinder forest and no-till (NT). Among tillage practices (plow, chisel and NT) only the 0-5 cm soil layer under NT exhibited higher SOC and N concentrations. An analysis of the literature of NT effect on SOC stocks. using meta-analysis, suggested that NT would have an overall positive effect on SOC sequestration rate but with a greater variability of what was previously reported. The average sequestration rate of NT was 330 kg SOC ha(-1) year(-1) with a 95%, confidence interval ranging from 47 to 620 kg SOC ha(-1) year(-1). There was no effect of soil texture or crop rotation on the SOC sequestration rate that could year explain this variability. The conversion factor for SOC stock changes from plow to NT was equal to 1.04. This suggests that the complex mechanisms and pathways of SOC accrual warrant a cautious approach when generalizing the beneficial changes of NT on SOC stocks. (C) 2004 Elsevier B.V. All rights reserved.
  • Authors:
    • Bucholtz, S.
    • Roberts, M. J.
    • .
  • Source: American Journal of Agricultural Economics
  • Volume: 87
  • Issue: 1
  • Year: 2005
  • Summary: The Conservation Reserve Program (CRP) pays farmers about $2 billion per year to retire cropland under ten- to fifteen- year contracts. Recent research by Wu found that slippage- an unintended stimulus of new plantings- offsets some of CRP's environmental benefits. Wu does not account for the endogeneity of CRP enrollments. Furthermore, the data used by Wu cannot be used to estimate slippage arising from a price feedback effect. We replicate Wu's findings, demonstrate the possible presence of spurious correlation, and construct new estimates with corrections for endogeneity and other econometric problems. We find no convincing evidence of slippage.
  • Authors:
    • Janzen, H. H.
    • Rochette, P.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 73
  • Year: 2005
  • Summary: The Intergovernmental Panel on Climate Change (IPCC) standard methodology to conduct national inventories of soil N2O emissions is based on default (or Tier I) emission factors for various sources. The objective of our study was to summarize recent N2O flux data from agricultural legume crops to assess the emission factor associated with rhizobial nitrogen fixation. Average N2O emissions from legumes are 1.0 kg Nha-1 for annual crops, 1.8 kg N ha-1 for pure forage crops and 0.4 kg N ha-1 for grass legume mixes. These values are only slightly greater than background emissions from agricultural crops and are much lower that those predicted using 1996 IPCC methodology. These field flux measurements and other process-level studies offer little support for the use of an emission factor for biological N fixation (BNF) by legume crops equal to that for fertiliser N. We conclude that much of the increase in soil N2O emissions in legume crops may be attributable to the N release from root exudates during the growing season and from decomposition of crop residues after harvest, rather than from BNF per se. Consequently, we propose that the biological fixation process itself be removed from the IPCC N2O inventory methodology, and that N2O emissions induced by the growth of legume crops be estimated solely as a function of crop residue decomposition using an estimate of above- and below-ground residue inputs, modified as necessary to reflect recent findings on N allocation.
  • Authors:
    • Mallarino, A. P.
    • Parkin, T. B.
    • Laird, D. A.
    • Russell, A. E.
  • Source: Soil Science Society of America Journal
  • Volume: 69
  • Issue: 2
  • Year: 2005
  • Summary: Growing interest in the potential for agricultural soils to provide a sink for atmospheric C has prompted studies of effects of management on soil organic carbon (SOC) sequestration. We analyzed the impact on SOC of four N fertilization rates (0-270 kg N ha-1) and four cropping systems: continuous corn (CC) (Zea mays L.); corn-soybean [Glycine max (L.) Merr.] (CS); corn-corn-oat-alfalfa (oat, Avena sativa L.; alfalfa, Medicago sativa L.) (CCOA), and corn-oat-alfalfa-alfalfa (COAA). Soils were sampled in 2002, Years 23 and 48 of the experiments located in northeast and north-central Iowa, respectively. The experiments were conducted using a replicated split-plot design under conventional tillage. A native prairie was sampled to provide a reference (for one site only). Cropping systems that contained alfalfa had the highest SOC stocks, whereas the CS system generally had the lowest SOC stocks. Concentrations of SOC increased significantly between 1990 and 2002 in only two of the nine systems for which historical data were available, the fertilized CC and COAA systems at one site. Soil quality indices such as particulate organic carbon (POC) were influenced by cropping system, with CS < CC < CCOA. In the native prairie, SOC, POC, and resistant C concentrations were 2.8, 2.6, and 3.9 times, respectively, the highest values in cropped soil, indicating that cultivated soils had not recovered to precultivation conditions. Although corn yields increased with N additions, N fertilization increased SOC stocks only in the CC system at one site. Considering the C cost for N fertilizer production, N fertilization generally had a net negative effect on C sequestration.