• Authors:
    • Robertson, G. P.
    • Kravchenko, A. N.
    • Basso, B.
    • Senthilkumar, S.
  • Source: Soil Science Society of America Journal
  • Volume: 73
  • Issue: 6
  • Year: 2009
  • Summary: Temporal changes in soil C content vary as a result of complex interactions among different factors including climate, baseline soil C levels, soil texture, and agricultural management practices. The study objectives were: to estimate the changes in soil total C contents that occurred in the past 18 to 21 yr in soils under agricultural management and in never-tilled grassland in southwest Michigan; to explore the relationships between these changes and soil properties, such as baseline C levels and soil texture; and to simulate C changes using a system approach model (SALUS). The data were collected from two long-term experiments established in 1986 and 1988. Georeferenced samples were collected from both experiments before establishment and then were resampled in 2006 and 2007. The studied agricultural treatments included the conventional chisel-plow and no-till management systems with and without N fertilization and the organic chisel-plow management with cover crops. Total C was either lost in the conventional chisel-plowed systems or was only maintained at the 1980s levels by the conservation management systems. The largest loss in the agricultural treatments was 4.5 Mg ha(-1) total C observed in the chisel-plow system without N fertilization. A loss of 17.3 Mg ha(-1) occurred in the virgin grassland sod. Changes in C content tended to be negatively related to baseline C levels. Under no-till, changes in C were positively related to silt + clay contents. The SALUS predictions of soil C changes were in excellent agreement with the observed data for most of the agricultural treatments and for the virgin soil.
  • Authors:
    • Robertson, G. P.
    • Kravchenko, A. N.
    • Senthilkumar, S.
  • Source: Soil Science Society of America Journal
  • Volume: 73
  • Issue: 6
  • Year: 2009
  • Summary: Topography is one of the major factors affecting sod C and N contents at the field/landscape level. However, topographical effects are likely to differ in magnitude in different agricultural systems. The objective of this study was to examine the interactions between topography and management systems on Soil C and N. The study was conducted at the Kellogg Biological Station Long-Term Ecological Research (LTER) site in southwest Michigan. The studied treatments were chisel-plow (CT) and no-till (NT) with conventional chemical inputs and a chisel-plow organic management system with winter leguminous cover crops (CT-cover). At the 0- to 5-cm depth in both upperslope and valley positions total C and N contents of NT management were the highest followed by CT-cover and then CT At 0- to 15-, 20- to 30-, and 30- to 40-cm depths, treatment effects varied depending on the landscape position. There were no differences among the treatments in upperslopes, while in the valleys total C and N tended to be the highest in NT and CT-cover followed by CT. The results indicated the importance of accounting for interaction between topography and management practices when assessing C sequestration across landscapes with varying topography. Total C stocks at the 0- to 30-cm depths were around 35,32, and 27 MgC ha(-1) soil (+/- 2 MgC ha(-1) standard error) in CT-cover, NT and CT respectively, across upperslopes and valleys. Overall, CT-cover was found to be as efficient in maintaining C and N content as no-till with conventional chemical inputs. Power analysis for C and N stocks at the 0- to 40-cm depth revealed that because of high variability in total C and N stocks at greater depths, the 10 to 30 samples per treatment available in this study were inadequate to detect differences in C and N stocks if the differences were < 26 MgC ha(-1).
  • Authors:
    • Service, R. F.
  • Source: Science
  • Volume: 326
  • Issue: 5952
  • Year: 2009
  • Summary: At first blush, it's easy to make the case for biofuels. By converting crops into ethanol or biodiesel, farmers can reduce demand for imported oil, lower national dependence on authoritarian governments in the Middle East, and potentially cut greenhouse gas emissions. But dig a little deeper, and the story gets more complicated. Biofuels promise energy and climate gains, but in some cases, those improvements wouldn't be dramatic. And they come with some significant downsides, such as the potential for increasing the price of corn and other food staples. Now, a series of recent studies is underscoring another risk: A widespread shift toward biofuels could pinch water supplies and worsen water pollution. In short, an increased reliance on biofuel trades an oil problem for a water problem.
  • Authors:
    • De Moura, R. L.
    • Klonsky, K. M.
    • Smith, R. F.
  • Source: University of California Cooperative Extension Publication
  • Year: 2009
  • Authors:
    • De Moura, R. L.
    • Klonsky, K. M.
    • Smith, R. F.
  • Source: University of California Cooperative Extension Publication
  • Year: 2009
  • Authors:
    • Fixen, P. E.
    • Jensen, T. L.
    • Bruulsema, T. W.
    • Snyder, C. S.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 133
  • Issue: 3-4
  • Year: 2009
  • Summary: Fertilizer nitrogen (N) use is expanding globally to satisfy food, fiber, and fuel demands of a growing world population. Fertilizer consumers are being asked to improve N use efficiency through better management in their fields, to protect water resources and to minimize greenhouse gas (GHG) emissions, while sustaining soil resources and providing a healthy economy. A review of the available science on the effects of N source, rate, timing, and placement, in combination with other cropping and tillage practices, on GHG emissions was conducted. Implementation of intensive crop management practices, using principles of ecological intensification to enhance efficient and effective nutrient uptake while achieving high yields, was identified as a principal way to achieve reductions in GHG emissions while meeting production demands. Many studies identified through the review involved measurements of GHG emissions over several weeks to a few months, which greatly limit the ability to accurately determine system-level management effects on net global warming potential. The current science indicates: (I) appropriate fertilizer N use helps increase biomass production necessary to help restore and maintain soil organic carbon (SOC) levels; (2) best management practices (BMPs) for fertilizer N play a large role in minimizing residual soil nitrate, which helps lower the risk of increased nitrous oxide (N2O) emissions; (3) tillage practices that reduce soil disturbance and maintain crop residue on the soil surface can increase SOC levels, but usually only if crop productivity is maintained or increased; (4) differences among fertilizer N sources in N2O emissions depend on site- and weather-specific conditions; and (5) intensive crop management systems do not necessarily increase GHG emissions per unit of crop or food production; they can help spare natural areas from conversion to cropland and allow conversion of selected lands to forests for GHG mitigation, while supplying the world's need for food, fiber, and biofuel. Transfer of the information to fertilizer dealers, crop advisers, farmers, and agricultural and environmental authorities should lead to increased implementation of fertilizer BMPs, and help to reduce confusion over the role of fertilizer N on cropping system emissions of GHGs. Gaps in scientific understanding were identified and will require the collaborative attention of agronomists, soil scientists, ecologists, and environmental authorities in serving the immediate and long-term interests of the human population. (C) 2009 Elsevier B.V. All rights reserved.
  • Authors:
    • Reicosky, D. C.
    • Baker, J. M.
    • Koskinen, W. C.
    • Spokas, K. A.
  • Source: Chemosphere
  • Volume: 77
  • Issue: 4
  • Year: 2009
  • Summary: A potential abatement to increasing levels of carbon dioxide (CO2) in the atmosphere is the use of pyrolysis to convert vegetative biomass into a more stable form of carbon (biochar) that could then be applied to the soil. However, the impacts of pyrolysis biochar on the soil system need to be assessed before initiating large scale biochar applications to agricultural fields. We compared CO2 respiration, nitrous oxide (N2O) production, methane (CH4) oxidation and herbicide retention and transformation through laboratory incubations at field capacity in a Minnesota soil (Waukegan silt loam) with and without added biochar. CO2 originating from the biochar needs to be subtracted from the soil-biochar combination in order to elucidate the impact of biochar on soil respiration. After this correction, biochar amendments reduced CO2 production for all amendment levels tested (2, 5, 10, 20, 40 and 60% w/w; corresponding to 24-720 t ha -1 field application rates). In addition, biochar additions suppressed N2O production at all levels. However, these reductions were only significant at biochar amendment levels >20% w/w. Biochar additions also significantly suppressed ambient CH4 oxidation at all levels compared to unamended soil. The addition of biochar (5% w/w) to soil increased the absorption of atrazine and acetochlor compared to non-amended soils, resulting in decreased dissipation rates of these herbicides. The recalcitrance of the biochar suggests that it could be a viable carbon sequestration strategy, and might provide substantial net greenhouse gas benefits if the reductions in N2O production are lasting.
  • Authors:
    • Reicosky, D. C.
    • Spokas, K. A.
  • Source: Annals of Environmental Science
  • Volume: 3
  • Year: 2009
  • Summary: One potential abatement strategy to increasing atmospheric levels of carbon dioxide (CO2) is to sequester atmospheric CO2 captured through photosynthesis in biomass and pyrolysed into a more stable form of carbon called biochar. We evaluated the impacts of 16 different biochars from different pyrolysis/gasification processes and feed stock materials (corn stover, peanut hulls, macadamia nut shells, wood chips, and turkey manure plus wood chips) as well as a steam activated coconut shell charcoal on net CO2, methane (CH4) and nitrous oxide (N2O) production/consumption potentials through a 100 day laboratory incubation with a Minnesota agricultural soil (Waukegan silt loam, total organic carbon = 2.6%); Wisconsin forest nursery soil (Vilas loamy sand, total organic carbon = 1.1%); and a California landfill cover soil (Marina loamy sand plus green waste-sewage sludge, total organic carbon = 3.9%) at field capacity (soil moisture potential = -33 kPa). After correcting for the CO2, CH4 and N2O production of the char alone, the addition of biochars (10% w/w) resulted in different responses among the soils. For the agricultural soil, five chars increased, three chars reduced and eight had no significant impact on the observed CO2 respiration. In the forest nursery soil, three chars stimulated CO2 respiration, while the remainder of the chars suppressed CO2 respiration. In the landfill cover soil, only two chars increased observed CO2 respiration, with the remainder exhibiting lower CO2 respiration rates. All chars and soil combinations resulted in decreased or unaltered rates of CH4 oxidation, with no increases observed in CH4 oxidation or production activity. Biochar additions generally suppressed observed N2O production, with the exception being high nitrogen compost-amended biochar, which increased N2O production. The general conclusions are: (1) the impact on trace gas production is both dependent on the biochar and soil properties and (2) biochar amendments initially reduce microbial activity in laboratory incubations. These preliminary results show a wide diversity in biochar properties that point to the need for more research.
  • Authors:
    • Sims, P. L.
    • Schuman, G. E.
    • Saliendra, N. Z.
    • Morgan, J. A.
    • Mielnick, P.
    • Mayeux, H.
    • Johnson, D. A.
    • Haferkamp, M.
    • Gilmanov, T. G.
    • Frank, A. B.
    • Emmerich, W.
    • Dugas, W.
    • Bradford, J. A.
    • Angell, R.
    • Svejcar, T.
    • System Planning Corporation
    • Snyder, K.
  • Source: related: RANGELAND ECOLOGY & MANAGEMENT
  • Volume: 61
  • Issue: 5
  • Year: 2009
  • Summary: related, see: http://lca.usgs.gov/lca/fluxnet/index.php
  • Authors:
    • U.S. EPA
  • Year: 2009
  • Summary: The United States Environmental Protection Agency (EPA) prepares the official U.S. Inventory of Greenhouse Gas Emissions and Sinks to comply with existing commitments under the United Nations Framework Convention on Climate Change (UNFCCC). This chapter summarizes the latest information on U.S. anthropogenic greenhouse gas emission trends from 1990 through 2007. In 2007, total U.S. greenhouse gas emissions were 7,150.1 Tg CO2 Eq. Overall, total U.S. emissions have risen by 17 percent from 1990 to 2007. Emissions rose from 2006 to 2007, increasing by 1.4 percent (99.0 Tg CO2 Eq.). The following factors were primary contributors to this increase: (1) cooler winter and warmer summer conditions in 2007 than in 2006 increased the demand for heating fuels and contributed to the increase in the demand for electricity, (2) increased consumption of fossil fuels to generate electricity and (3) a significant decrease (14.2 percent) in hydropower generation used to meet this demand.