• Authors:
    • Walsh, M.
    • Roberts, R.
    • Wilson, B.
    • Menard, R. J.
    • Hellwinckel, C.
    • Jensen, K.
    • de la Torre Ugarte, D. G.
    • English, B. C.
  • Year: 2006
  • Summary: from exec summary: "This study was designed to determine the feasibility of America's farms, forests and ranches providing 25 percent of U.S. total energy needs while continuing to produce safe, abundant and affordable food, feed and fiber. In addition, the analysis looks at the associated impacts of achieving the goal on the agricultural sector and the nation's overall economy.... to meet the 25x-25 goal of 29.42 quads, an additional 15.45 quads would need to come from agricultural and forestry lands. Key findings in this analysis: America's farms, forests and ranches can play a significant role in meeting the country's renewable energy needs. The 25x-25 goal is achievable. Continued yield increases in major crops, strong contributions from the forestry sector, utilization of food processing wastes, as well as the use of over one hundred million acres of dedicated energy crops, like switchgrass, will all contribute toward meeting this goal. A combination of all of these new and existing sources can provide sufficient feedstock for the additional 15.45 quads of renewable energy needed. The 25x25 goal can be met while allowing the ability of the agricultural sector to reliably produce food, feed and fiber at reasonable prices. Reaching the goal would have an extremely favorable impact on rural America and the nation as a whole. Including multiplier effects through the economy, the projected annual impact on the nation from producing and converting feedstocks into energy would be in excess of $700 billion in economic activity and 5.1 million jobs in 2025, most of that in rural areas. By reaching the 25X-25 energy goal, the total addition to net farm income could reach $180 billion, as the market rewards growers for producing alternative energy and enhancing our national security. In 2025 alone, net farm income would increase by $37 billion compared with USDA baseline projections. Reaching the goal would also have significant positive price impacts on crops. In the year 2025, when compared with USDA baseline projections, national average per bushel crop prices are projected to be $0.71 higher for corn, $0.48 higher for wheat, and $2.04 higher for soybeans. With higher market prices, an estimated cumulative savings in government payments of $15 billion could occur. This does not include potential savings in fixed/direct or Conservation Reserve Program (CRP) payments. In the near term, corn acres are projected to increase. As cellulosic ethanol becomes commercially viable after 2012, the analysis predicts major increases in acreage for a dedicated energy crop like switchgrass. The higher feed crop prices do not result in a one-to-one increase in feed expenses for the livestock industry. Increases in ethanol and biodiesel production result in more distillers dried grains (DDG's) and soybean meal, which partially compensate for increased corn prices. Moreover, the integrated nature of the industry allows for the adjustment of animal inventories as a way to adjust to the environment and increase net returns. In addition, the production of energy from manure and tallow could provide additional value for the industry. Contributions from America's fields, farms and forests could result in the production of 86 billion gallons of ethanol and 1.2 billion gallons of biodiesel, which has the potential to decrease gasoline consumption by 59 billion gallons in 2025. The production of 14.19 quads of energy from biomass and wind sources could replace the growing demand for natural gas, diesel, and/or coal generated electricity. These renewable energy resources could significantly decrease the nation's reliance on foreign oil, fossil fuels, and enhance the national security of all Americans.
  • Authors:
    • Bourbonniere, R. A.
    • Warner, B. G.
    • Robarts, R. D.
    • Murkin, H. R.
    • McDougal, R. L.
    • Olness, A.
    • Gleason, R. A.
    • Euliss, N. H. Jr.
  • Source: Science of the Total Environment
  • Volume: 361
  • Issue: 1-3
  • Year: 2006
  • Summary: We evaluated the potential of prairie wetlands in North America as carbon sinks. Agricultural conversion has resulted in the average loss of 10.1 Mg ha(-1) of soil organic carbon on over 16 million ha of wetlands in this region. Wetland restoration has potential to sequester 378 Tg of organic carbon over a 10-year period. Wetlands can sequester over twice the organic carbon as no-till cropland on only about 17% of the total land area in the region. We estimate that wetland restoration has potential to offset 2.4% of the annual fossil CO2 emission reported for North America in 1990. (c) 2005 Elsevier B.V. All rights reserved.
  • Authors:
    • Nielsen, D. C.
    • Lyon, D. J.
    • Felter, D. G.
  • Source: Agronomy Journal
  • Volume: 98
  • Issue: 6
  • Year: 2006
  • Summary: Substituting a short-season, spring-planted crop for summer fallow when soil water is sufficient at planting might reduce soil degradation without significantly increasing the risk of crop failure. The objectives of this study were to determine the relationship of crop grain or forage yield to plant available soil water at planting. The study was conducted on silt loam soils in 2004 and 2005 at Sidney, NE, and Akron, CO. A range of soil water levels was established with supplemental irrigation before planting. Four crops [spring triticale (X Triticosecale rimpaui Wittm.) for forage, dry pea (Pisum sativum L.) for grain, proso millet (Panicum miliaceum L.) for grain, and foxtail millet (Setaria italica L. Beauv.) for forage] were no-till seeded into corn (Zea mays L.) residue in a split-plot design with four replications per location. Triticale forage yield increased by 229 kg ha-1 for each centimeter of soil water available at planting in 2004. Foxtail millet forage yield and grain yield of proso millet increased by 399 kg ha-1 cm-1 and 148 kg ha-1 cm-1, respectively, at Akron in 2004. Spring triticale, foxtail millet, and proso millet did not respond to soil water at planting in 2005, when precipitation was above the long-term average. Dry pea did not demonstrate a consistent positive response to soil water availability at planting. Soil water at planting may be a useful indicator of potential yield for selected short-season spring-planted summer crops, particularly when crop production is limited by growing season precipitation.
  • Authors:
    • Caswell, M.
    • Fernandez-Cornejo, J.
  • Source: Economic Information Bulletin Number 11
  • Volume: 11
  • Year: 2006
  • Authors:
    • Tanaka, D. L.
    • Liebig, M. A.
    • Frank, A. B.
  • Source: Soil & Tillage Research
  • Volume: 89
  • Issue: 1
  • Year: 2006
  • Summary: Soil respiration is a process influenced by land use, management practices, and environmental conditions. Our objectives were to evaluate relationships between management-induced differences in soil organic carbon (SOC) and soil CO2 efflux from continuous no-till spring wheat (Triticum aestivum L.), spring wheat-fallow under no-till, and a native mixed-grass prairie with grazing near Mandan, ND. A Werner-Sen-Chama soil complex (Entic Haplustoll, Typic Haplustoll, and Typic Calciustoll) was present at the grassland site and a Wilton silt loam (Pachic Haplustoll) at the cropping sites. Soil chambers were used to measure soil CO2 effluxes about every 21 days starting 14 May 2001 to 1 April 2003. Soil water and soil temperature were measured at time of CO2 efflux measurements. Soil organic carbon, microbial biomass carbon (MBC), and above and belowground plant biomass were measured in mid-July each year. Root biomass to 0.3 m depth of the undisturbed grassland was significantly greater (12.3 Mg ha-1) than under continuous wheat (1.3 Mg ha-1) and wheat-fallow (0.3 Mg ha-1). Grassland SOC content of 84 Mg ha-1 to 0.3 m soil depth was 1.2 times greater than continuous wheat and 1.3 times greater than wheat-fallow. The MBC of the grassland was 2.2 Mg ha-1, or 3.6 times greater than continuous wheat and 7.2 times greater than wheat-fallow treatments. Soil CO2 efflux averaged 2.8 g CO2-C m-2 day-1 for grassland, compared to 1.9 g CO2-C m-2 day-1 for wheat fallow and 1.6 g CO2-C m-2 day-1 for continuous wheat treatments. Although these CO2 efflux rates were based on measurements made at intervals of about 21 days, the differences among treatments with time were rather consistent. Differences in soil CO2 efflux among treatments could be attributed to differences in SOC and MBC, suggesting that land use plays a significant role in soil CO2 efflux from respiration.
  • Authors:
    • Robertson, G. P.
    • Parr, S.
    • Loecke, T. D.
    • Grandy, A. S.
  • Source: Journal of Environmental Quality
  • Volume: 35
  • Issue: 4
  • Year: 2006
  • Summary: No-till cropping can increase soil C stocks and aggregation but patterns of long-term changes in N2O emissions, soil N availability, and crop yields still need to be resolved. We measured soil C accumulation, aggregation, soil water, N2O emissions, soil inorganic N, and crop yields in till and no-till corn-soybean-wheat rotations between 1989 and 2002 in southwestern Michigan and investigated whether tillage effects varied over time or by crop. Mean annual NO3- concentrations in no-till were significantly less than in conventional till in three of six corn years and during one year of wheat production. Yields were similar in each system for all 14 years but three, during which yields were higher in no-till, indicating that lower soil NO3- concentrations did not result in lower yields. Carbon accumulated in no-till soils at a rate of 26 g C m-2 yr-1 over 12 years at the 0- to 5-cm soil depth. Average nitrous oxide emissions were similar in till (3.27 {+/-} 0.52 g N ha d-1) and no-till (3.63 {+/-} 0.53 g N ha d-1) systems and were sufficient to offset 56 to 61% of the reduction in CO2 equivalents associated with no-till C sequestration. After controlling for rotation and environmental effects by normalizing treatment differences between till and no-till systems we found no significant trends in soil N, N2O emissions, or yields through time. In our sandy loam soils, no-till cropping enhances C storage, aggregation, and associated environmental processes with no significant ecological or yield tradeoffs.
  • Authors:
    • Tiffany, D.
    • Polasky, S.
    • Tilman, David
    • Nelson, E.
    • Hill, J.
  • Source: Proceedings of the National Academy of Sciences of the United States of America
  • Volume: 103
  • Issue: 30
  • Year: 2006
  • Summary: Negative environmental consequences of fossil fuels and concerns about petroleum supplies have spurred the search for renewable transportation biofuels. To be a viable alternative, a biofuel should provide a net energy gain, have environmental benefits, be economically competitive, and be producible in large quantities without reducing food supplies. We use these criteria to evaluate, through life-cycle accounting, ethanol from corn grain and biodiesel from soybeans. Ethanol yields 25% more energy than the energy invested in its production, whereas biodiesel yields 93% more. Compared with ethanol, biodiesel releases just 1.0%, 8.3%, and 13% of the agricultural nitrogen, phosphorus, and pesticide pollutants, respectively, per net energy gain. Relative to the fossil fuels they displace, greenhouse gas emissions are reduced 12% by the production and combustion of ethanol and 41% by biodiesel. Biodiesel also releases less air pollutants per net energy gain than ethanol. These advantages of biodiesel over ethanol come from lower agricultural inputs and more eficient conversion of feedstocks to fuel. Neither biofuel can replace much petroleum without impacting food supplies. Even dedicating all U.S. corn and soybean production to biofuels would meet only 12% of gasoline demand and 6% of diesel demand. Until recent increases in petroleum prices, high production costs made biofuels unprofitable without subsidies. Biodiesel provides suficient environmental advantages to merit subsidy. Transportation biofuels such as synfuel hydrocarbons or cellulosic ethanol, if produced from low-input biomass grown on agriculturally marginal land or from waste biomass, could provide much greater supplies and environmental benefits than food-based biofuels.
  • Authors:
    • Chong, G. W.
    • Martinson, E. J.
    • Omi, P. N.
    • Hunter, M. E.
  • Source: International Journal of Wildland Fire
  • Volume: 15
  • Issue: 2
  • Year: 2006
  • Summary: Establishment and spread of non-native species following wildfires can pose threats to long-term native plant recovery. Factors such as disturbance severity, resource availability, and propagule pressure may influence where non-native species establish in burned areas. In addition, pre- and post-fire management activities may influence the likelihood of non-native species establishment. In the present study we examine the establishment of non-native species after wildfires in relation to native species richness, fire severity, dominant native plant cover, resource availability, and pre- and post-fire management actions (fuel treatments and post-fire rehabilitation treatments). We used an information-theoretic approach to compare alternative hypotheses. We analysed post-fire effects at multiple scales at three wildfires in Colorado and New Mexico. For large and small spatial scales at all fires, fire severity was the most consistent predictor of non-native species cover. Non-native species cover was also correlated with high native species richness, low native dominant species cover, and high seeded grass cover. There was a positive, but non-significant, association of non-native species with fuel-treated areas at one wildfire. While there may be some potential for fuels treatments to promote non-native species establishment, wildfire and post-fire seeding treatments seem to have a larger impact on non-native species.
  • Authors:
    • Bremer, D.
  • Year: 2006
  • Summary: 1) Quantify the magnitude and patterns of nitrous oxide (N2O) fluxes in turfgrass; and 2) determine how nitrogen (N)-fertilization rates, N-fertilizer types, and irrigation affect N2O fluxes.
  • Authors:
    • Trettin, C. C.
    • Bliss, N. B.
    • Keller, J. K.
    • Megonigal, J. P.
    • Bridgham, S. D.
  • Source: Wetlands
  • Volume: 26
  • Issue: 4
  • Year: 2006
  • Summary: We examine the carbon balance of North American wetlands by reviewing and synthesizing the published literature and soil databases. North American wetlands contain about 220 Pg C, most of which is in peat. They are a small to moderate carbon sink of about 49 Tg C yr(-1), although the uncertainty around this estimate is greater than 100%, with the largest unknown being the role of carbon sequestration by sedimentation in freshwater mineral-soil wetlands. We estimate that North American wetlands emit 9 Tg methane (CH4) yr(-1); however, the uncertainty of this estimate is also greater than 100%. With the exception of estuarine wetlands, CH4 emissions from wetlands may largely offset any positive benefits of carbon sequestration in soils and plants in terms of climate forcing. Historically, the destruction of wetlands through land-use changes has had the largest effects on the carbon fluxes and consequent radiative forcing of North American wetlands. The primary effects have been a reduction in their ability to sequester carbon (a small to moderate increase in radiative forcing), oxidation of their soil carbon reserves upon drainage (a small increase in radiative forcing), and reduction in CH4 emissions (a small to large decrease in radiative forcing). It is uncertain how global changes will affect the carbon pools and fluxes of North American wetlands. We will not be able to predict accurately the role of wetlands as potential positive or negative feedbacks to anthropogenic global change without knowing the integrative effects of changes in temperature, precipitation, atmospheric carbon dioxide concentrations, and atmospheric deposition of nitrogen and sulfur on the carbon balance of North American wetlands.