• Authors:
    • Sauer, T.
    • Soolaneyakanahally, R.
    • de Gooijer, H.
    • Bentrup, G.
    • Schoeneberger, M.
    • Brendle, J.
    • Zhou, X.
    • Current, D.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 5
  • Year: 2012
  • Authors:
    • McKone, T. E.
    • Horvath, A.
    • Santero, N. J.
    • Masanet, E.
    • Lobscheid, A. B.
    • Strogen, B.
    • Mishra, U.
    • Nazaroff, W. W.
    • Scown, C. D.
  • Source: Environmental Research Letters
  • Volume: 7
  • Issue: 1
  • Year: 2012
  • Summary: The Energy Independence and Security Act of 2007 set an annual US national production goal of 39.7 billion 1 of cellulosic ethanol by 2020. This paper explores the possibility of meeting that target by growing and processing Miscanthus x giganteus. We define and assess six production scenarios in which active cropland and/or Conservation Reserve Program land are used to grow to Miscanthus. The crop and biorefinery locations are chosen with consideration of economic, land-use, water management and greenhouse gas (GHG) emissions reduction objectives. Using lifecycle assessment, the net GHG footprint of each scenario is evaluated, providing insight into the climate costs and benefits associated with each scenario's objectives. Assuming that indirect land-use change is successfully minimized or mitigated, the results suggest two major drivers for overall GHG impact of cellulosic ethanol from Miscanthus: (a) net soil carbon sequestration or emissions during Miscanthus cultivation and (b) GHG offset credits for electricity exported by biorefineries to the grid. Without these factors, the GHG intensity of bioethanol from Miscanthus is calculated to be 11-13 g CO2-equivalent per MJ of fuel, which is 80-90% lower than gasoline. Including soil carbon sequestration and the power-offset credit results in net GHG sequestration up to 26 g CO2-equivalent per MJ of fuel.
  • Authors:
    • Lence, S.
    • Livingston, M.
    • Greene, C.
    • Chase, C.
    • Delate, K.
    • Singerman, A.
    • Hart, C.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 27
  • Issue: 4
  • Year: 2012
  • Summary: Emphasis on reducing emissions from the greenhouse gases (GHG), carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) has increased in recent years in the USA, primarily for industry, transportation, energy and agricultural sectors. In this study, we utilized on-farm data collected by the USDA-National Agricultural Statistics Service (NASS) Agricultural Resource Management Survey (ARMS), secured under an agreement with the USDA-Economic Research Service (ERS) to analyze the profitability of organic and conventional soybean production, based on changes that 'green payments' in a cap-and-trade system would introduce in agricultural markets in the USA. In particular, the analysis focused on establishing whether organic producers would be better positioned to sequester carbon (C) and reap the benefits of the C-offset scheme compared to conventional producers, given the differences in costs, management practices and environmental benefits between organic and conventional production methods. We estimated several changes in profitability of soybean producers according to management practices, incentives for the generation of offset credits, and increase in energy input prices that a potential cap-and-trade system may introduce in future agricultural markets in the USA. Survey data suggested that even with lower yields, conventional producers could profit from converting to organic agriculture, given organic price premiums. In addition, taking into consideration both direct and indirect costs, average cost for conventional-till (CT) organic soybean production was approximately 9% lower than no-till (NT) conventional production. With a C market and payments for soil C sequestration through potential Clean Energy legislation, additional profit could be accrued by organic producers, because organic production would have 28% greater ton CO2 eq. acre(-1) yr(-1) sequestration than conventional NT. Thus, the environmental benefits from GHG reduction could incentivize increased conversion from conventional to organic production across the USA.
  • Authors:
    • Prior, S.
    • Torbert, H.
    • Way, T.
    • Watts, D.
    • Smith, K.
  • Source: Pedosphere
  • Volume: 22
  • Issue: 5
  • Year: 2012
  • Summary: Tillage and fertilization practices used in row crop production are thought to alter greenhouse gas emissions from soil. This study was conducted to determine the impact of fertilizer sources, land management practices, and fertilizer placement methods on greenhouse gas (CO2, CH4, and N2O) emissions. A new prototype implement developed for applying poultry litter in subsurface bands in the soil was used in this study. The field site was located at the Sand Mountain Research and Extension Center in the Appalachian Plateau region of northeast Alabama, USA, on a Hartsells fine sandy loam (fine-loamy, siliceous, subactive, thermic Typic Hapludults). Measurements of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions followed GRACEnet (greenhouse gas reduction through agricultural carbon enhancement network) protocols to assess the effects of different tillage (conventional vs. no-tillage) and fertilizer placement (subsurface banding vs. surface application) practices in a corn (Zea mays L.) cropping system. Fertilizer sources were urea-ammonium nitrate (UAN), ammonium nitrate (AN) and poultry litter (M) applied at a rate of 170 kg ha(-1) of available N. Banding of fertilizer resulted in the greatest concentration of gaseous loss (CO2 and N2O) compared to surface applications of fertilizer. Fertilizer banding increased CO2 and N2O loss on various sampling days throughout the season with poultry litter banding emitting more gas than UAN banding. Conventional tillage practices also resulted in a higher concentration of CO2 and N2O loss when evaluating tillage by sampling day. Throughout the course of this study, CH4 flux was not affected by tillage, fertilizer source, or fertilizer placement method. These results suggest that poultry litter use and banding practices have the potential to increase greenhouse gas emissions.
  • Authors:
    • Huggins, D.
    • Nelson, R.
    • Kemanian, A.
    • Higgins, S.
    • Stoeckle, C.
    • Marcos, J.
    • Collins, H.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 5
  • Year: 2012
  • Summary: Conservation tillage is an agricultural strategy to mitigate atmospheric greenhouse gas (GHG) emissions. In eastern Washington, we evaluated the long-term effects of conventional tillage (CT), reduced tillage (RT) and no-tillage (NT) on soil organic carbon (SOC) storage and nitrous oxide (N2O) emissions at three dryland and one irrigated location using the cropping systems simulation model CropSyst. Conversion of CT to NT produced the largest relative increase in SOC storage (Delta SOC, average yearly change relative to CT) in the top 30 cm (11.8 in) of soil where Delta SOC ranged from 0.29 to 0.53 Mg CO(2)e ha(-1) y(-1) (CO(2)e is carbon dioxide [CO2] equivalent of SOC; 0.13 to 0.24 tn CO(2)e ac(-1) yr(-1)).The Delta SOC were less with lower annual precipitation, greater fallow frequency, and when changing from CT to RT. Overall, Delta SOC decreased from the first to the third decade after conversion from CT to NT or RT. Simulations of Delta SOC for the conversion of CT to NT based on a 0 to 15 cm (0 to 5.9 in) soil depth were greater than the Delta SOC based on a 0 to 30 cm depth, primarily due to differences among tillage regimes in the depth-distribution of carbon (C) inputs and the resultant SOC distribution with depth. Soil erosion rates under CT in the study region are high, posing deleterious effects on soil quality, productivity, and aquatic systems. However, an analysis that includes deposition, burial, and sedimentation on terrestrial and aquatic systems of eroded SOC indicates that the substantial erosion reduction obtained with RT and NT may result only in minor additional SOC oxidation as compared to CT Simulated N2O emissions, expressed as CO2 equivalent, were not very different under CT, RT, and NT However, N2O emissions were sufficiently high to offset gains in SOC from the conversion of CT to RT or NT.Thus, reducing tillage intensity can result in net C storage, but mitigation of GHG is limited unless it is coupled with nitrogen (N) fertilizer management to also reduce N2O emission.
  • Authors:
    • Venkat, K.
  • Source: Journal of Sustainable Agriculture
  • Volume: 36
  • Issue: 6
  • Year: 2012
  • Summary: Given the growing importance of organic food production, there is a pressing need to understand the relative environmental impacts of organic and conventional farming methods. This study applies standards-based life cycle assessment to compare the cradle-to-farm gate greenhouse gas emissions of 12 crop products grown in California using both organic and conventional methods. In addition to analyzing steady-state scenarios in which the soil organic carbon stocks are at equilibrium, this study models a hypothetical scenario of converting each conventional farming system to a corresponding organic system and examines the impact of soil carbon sequestration during the transition. The results show that steady-state organic production has higher emissions per kilogram than conventional production in seven out of the 12 cases (10.6% higher overall, excluding one outlier). Transitional organic production performs better, generating lower emissions than conventional production in seven cases (17.7% lower overall) and 22.3% lower emissions than steady-state organic. The results demonstrate that converting additional cropland to organic production may offer significant GHG reduction opportunities over the next few decades by way of increasing the soil organic carbon stocks during the transition. Nonorganic systems could also improve their environmental performance by adopting management practices to increase soil organic carbon stocks.
  • Authors:
    • Frear, C.
    • Chen, S.
    • Wang, G.
  • Source: Geoderma
  • Volume: 170
  • Year: 2012
  • Summary: Quantitative information is critical in policy making related to the roles of agriculture in greenhouse gas (GHG) emissions. A Unit Response (UR) curve method was developed in this study for modeling GHG emissions from soil after liquid manure applications. The emission sources (soils and liquid manures) are conceptualized as a set of linear cascaded chambers with equal storage-release coefficients, or two sets of cascaded chambers in parallel, each set having equal storage-release coefficients. The model is based on a two-parameter gamma distribution. Three parameters in this model denote the number of cascaded chambers, the storage-release coefficient, and the multiplier (referring to the total net emissions) added to the gamma distribution function. These parameters can be expressed as functions of site-specific background fluxes without applications of manure/fertilizer. The method was assessed with emissions data from five fields in Washington State. The results showed that at the WSU and Lynden sites, the average excess CH4 emissions due to manure applications were 0.39 and 0.17 kg CH4-C ha(-1), respectively: the average excess CO2 emissions were 216.50 and 25.20 kg CO2-C ha(-1), respectively; and the average excess N2O were 0.37 and 0.03 kg N2O-N ha(-1), respectively. The UR method may fill the gaps between field measurements, simple emission factor (EF) method, and complex process-oriented models. This method has the potential to be used for estimating additional GHG emissions due to manure/fertilizer applications.
  • Authors:
    • Zhang, C.
    • Lu, C. Q.
    • Ren, W.
    • Liu, M. L.
    • Chen, G. S.
    • Tian, H. Q.
    • Xu, X. F.
  • Source: Biogeosciences
  • Volume: 9
  • Issue: 4
  • Year: 2012
  • Summary: Nitrous oxide (N2O) is a potent greenhouse gas which also contributes to the depletion of stratospheric ozone (O-3). However, the magnitude and underlying mechanisms for the spatiotemporal variations in the terrestrial sources of N2O are still far from certain. Using a process-based ecosystem model (DLEM - the Dynamic Land Ecosystem Model) driven by multiple global change factors, including climate variability, nitrogen (N) deposition, rising atmospheric carbon dioxide (CO2), tropospheric O-3 pollution, N fertilizer application, and land conversion, this study examined the spatial and temporal variations in terrestrial N2O flux over North America and further attributed these variations to various driving factors. From 1979 to 2010, the North America cumulatively emitted 53.9 +/- 0.9 Tg N2O-N (1 Tg = 10(12) g), of which global change factors contributed 2.4 +/- 0.9 Tg N2O-N, and baseline emission contributed 51.5 +/- 0.6 Tg N2O-N. Climate variability, N deposition, O-3 pollution, N fertilizer application, and land conversion increased N2O emission while the elevated atmospheric CO2 posed opposite effect at continental level; the interactive effect among multiple factors enhanced N2O emission over the past 32 yr. N input, including N fertilizer application in cropland and N deposition, and multi-factor interaction dominated the increases in N2O emission at continental level. At country level, N fertilizer application and multi-factor interaction made large contribution to N2O emission increase in the United States of America (USA). The climate variability dominated the increase in N2O emission from Canada. N inputs and multiple factors interaction made large contribution to the increases in N2O emission from Mexico. Central and southeastern parts of the North America - including central Canada, central USA, southeastern USA, and all of Mexico - experienced increases in N2O emission from 1979 to 2010. The fact that climate variability and multi-factor interaction largely controlled the inter-annual variations in terrestrial N2O emission at both continental and country levels indicate that projected changes in the global climate system may substantially alter the regime of N2O emission from terrestrial ecosystems during the 21st century. Our study also showed that the interactive effect among global change factors may significantly affect N2O flux, and more field experiments involving multiple factors are urgently needed.
  • Authors:
    • Cotrufo, M. F.
    • Stewart, C. E.
    • Zheng, J.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 5
  • Year: 2012
  • Summary: Biochar (BC) application to agricultural soils could potentially sequester recalcitrant C, increase N retention, increase water holding capacity, and decrease greenhouse gas (GHG) emissions. Biochar addition to soils can alter soil N cycling and in some cases decrease extractable mineral N (NO3- and NH4+) and N2O emissions. These benefits are not uniformly observed across varying soil types, N fertilization, and BC properties. To determine the effects of BC addition on N retention and GHG flux, we added two sizes (>250 and <250 mu m) of oak-derived BC (10% w/w) to two soils (aridic Argiustoll and aquic Haplustoll) with and without N fertilizer and measured extractable NO3- and NH4+ and GHG efflux (N2O, CO2, and CH4) in a 123-d laboratory incubation. Biochar had no effect on NO3-, NH4+, or N2O in the unfertilized treatments of either soil. Biochar decreased cumulative extractable NO3- in N fertilized treatments by 8% but had mixed effects on NH4+. Greenhouse gas efflux differed substantially between the two soils, but generally with N fertilizer BC addition decreased N2O 3 to 60%, increased CO2 10 to 21%, and increased CH4 emissions 5 to 72%. Soil pH and total treatment N (soil + fertilizer + BC) predicted soil N2O flux well across these two different soils. Expressed as CO2 equivalents, BC significantly reduced GHG emissions only in the N-fertilized silt loam by decreasing N2O flux. In unfertilized soils, CO2 was the dominant GHG component, and the direction of the flux was mediated by positive or negative BC effects on soil CO2 flux. On the basis of our data, the use of BC appears to be an effective management strategy to reduce N leaching and GHG emissions, particularly in neutral to acidic soils with high N content.
  • Authors:
    • Van Pelt, R. S.
    • Rice, C. W.
    • Nielsen, D.
    • Gulliford, J.
    • Delgado, J. A.
    • Lal, R.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 6
  • Year: 2012