• Authors:
    • Zgorelec, Z.
    • Bilandzija, D.
    • Kisic, I.
  • Source: Agriculturae Conspectus Scientificus
  • Volume: 79
  • Issue: 1
  • Year: 2014
  • Summary: Soil carbon stocks are highly vulnerable to human activities (such as tillage), which can decrease carbon stocks significantly. These activities break down soil's organic matter and some carbon is converted to carbon dioxide (CO 2). A part of CO 2 (a greenhouse gas that is one of the main contributor to global warming) is lost from the soil by soil respiration (soil CO 2 efflux). The aim of our study is to determine the soil carbon loss by soil CO 2 efflux under different tillage treatments. The experimental site is characterized by continental climate. Field experiment with six different tillage treatments usually used in this area was set up on Stagnic Luvisols in Daruvar, central lowland Croatia in 1994 with investigation aim on determination of soil degradation by water erosion and later, in 2011, expanded to the research on soil CO 2 efflux. Tillage treatments differed in tools that were used, depth and direction of tillage. Tillage treatments were: black fallow (BF), ploughing up/down the slope to 30 cm (PUDS), no-tillage (NT), ploughing across the slope to 30 cm (PAS), very deep ploughing across the slope to 50 cm (VDPAS) and subsoiling (50 cm) plus ploughing (30 cm) across the slope (SSPAS). Field measurements of soil CO 2 concentrations were conducted during one year (n=14) from November 2011 till November 2012, when cover crop was corn ( Zea mays L.). Preliminary soil sampling for determination of soil total carbon content was conducted in April 2011. This paper presents results of soil total carbon content in the soil surface layer (0-30 cm), the variations of CO 2-C efflux during the year, soil carbon loss by CO 2-C efflux and correlation between soil total carbon content and CO 2-C efflux. The range of soil surface total carbon content varied from 19083.7 kg/ha at BF treatment up to 31073.6 kg/ha at SSPAS treatment. The treatment with the lowest average measured CO 2-C efflux was BF. The average CO 2-C efflux at BF treatment was 7.9 kg CO 2-C/ha/day where CO 2-C efflux varied from 2.3 kg CO 2-C/ha/day up to 22.6 kg CO 2-C/ha/day. The treatment with the highest average measured CO 2-C efflux was NT. Range of CO 2-C efflux at NT treatment varied from 7.8 kg CO 2-C/ha/day up to 65.8 kg CO 2-C/ha/day and the average CO 2-C efflux was 24.4 kg CO 2-C/ha/day. Daily soil total carbon loss by soil respiration ranged from 0.04% at BF treatment up to 0.09% at NT treatment. Soil CO 2-C efflux was fully positively correlated with soil total carbon content (r=0.91). After all mentioned, it can be stated that in these agro-ecological conditions, best tillage practice in sustainable plant production in terms of the lowest daily soil total carbon loss (0.06%) by soil respiration is ploughing to 30 cm (PUDS and PAS). Still, it is necessary to conduct the total soil carbon balance in the future research for better understanding of soil carbon gains and losses.
  • Authors:
    • Schmidt, J.
    • Bryant, R.
    • Han, K.
    • Dell, C.
  • Source: American Society of Agronomy
  • Volume: 106
  • Issue: 2
  • Year: 2014
  • Summary: The use of enhanced efficiency N fertilizers can increase crop N utilization and lead to lower emissions of the greenhouse gas N2O. To determine the potential benefit of four enhanced efficiency fertilizers with rainfed corn (Zea mays L.) production in central Pennsylvania, N2O emissions and grain yield were monitored during a 4-yr field study and compared with untreated urea prills and urea-NH4NO3 (UAN). The tested enhanced efficiency products were ESN (polymer-coated urea), SuperU (urease and nitrification inhibitor treated urea), UAN treated with AgrotainPlus (urease and nitrification inhibitors), and PiNT (cation-stabilized amine-N). Additionally, 28-d laboratory incubations were conducted to verify the potential differences in N cycling rates among N sources. The laboratory incubations indicated that ESN, SuperU, and treated UAN all had the potential to delay accumulation of NO3 relative to untreated urea and UAN, but N cycling was similar with PiNT and the untreated fertilizers. Extended dry periods limited the denitrification potential and overall N2O emissions in the field, but spikes of N2O emission were seen within 1 mo after fertilizer application in each year. However, variation in emission rates was high within treatments, and no consistent differences among N sources were seen. Cumulative growing season N2O emissions and grain yield were similar for all N sources in each year of the study. Enhanced efficiency fertilizers do not appear to be an effective means to reduce N2O emission in a rainfed system, at least when rainfall is inconsistent.
  • Authors:
    • Soimakallio, S.
    • Holma, A.
    • Helin, T.
  • Source: International Journal of Life Cycle Assessment
  • Volume: 19
  • Issue: 4
  • Year: 2014
  • Summary: A framework for the inclusion of land use impact assessment and a set of land use impact indicators has been recently proposed for life cycle assessment (LCA) and no case studies are available for forest biomass. The proposed methodology is tested for Scandinavian managed forestry; a comparative case study is made for energy from wood, agro-biomass and peat; and sensitivity to forest management options is analysed. The functional unit of this comparative case study is 1 GJ of energy in solid fuels. The land use impact assessment framework of the United Nations Environment Programme and the Society of Environmental Toxicology and Chemistry (UNEP-SETAC) is followed and its application for wood biomass is critically analysed. Applied midpoint indicators include ecological footprint and human appropriation of net primary production, global warming potential indicator for biomass (GWP(bio)-100) and impact indicators proposed by UNEP-SETAC on ecosystem services and biodiversity. Options for forest biomass land inventory modelling are discussed. The system boundary covers only the biomass acquisition phase. Management scenarios are formulated for forest and barley biomass, and a sensitivity analysis focuses on impacts of land transformations for agro-biomass. Meaningful differences were found in between solid biofuels from distinct land use classes. The impact indicator results were sensitive to land occupation and transformation and differed significantly from inventory results. Current impact assessment method is not sensitive to land management scenarios because the published characterisation factors are still too coarse and indicate differences only between land use types. All indicators on ecosystem services and biodiversity were sensitive to the assumptions related with land transformation. The land occupation (m(2)a) approach in inventory was found challenging for Scandinavian wood, due to long rotation periods and variable intensities of harvests. Some suggestions of UNEP-SETAC were challenged for the sake of practicality and relevance for decision support. Land use impact assessment framework for LCA and life cycle impact assessment (LCIA) indicators could be applied in a comparison of solid bioenergy sources. Although forest bioenergy has higher land occupation than agro-bioenergy, LCIA indicator results are of similar magnitude or even lower for forest bioenergy. Previous literature indicates that environmental impacts of land use are significant, but it remains questionable if these are captured with satisfactory reliability with the applied LCA methodology, especially for forest biomass. Short and long time perspectives of land use impacts should be studied in LCA with characterisation factors for all relevant timeframes, not only 500 years, with a forward-looking perspective. Characterisation factors need to be modelled further for different (forest) land management intensities and for peat excavation.
  • Authors:
    • Laterra, P.
    • Alberto Studdert, G.
    • Horacio Villarino, S.
    • Gabriela Cendoya, M.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 185
  • Year: 2014
  • Summary: Soil organic carbon (SOC) plays a vital role in determining soil quality and health, but also SOC decrease contributes significantly to the increase in atmospheric CO2 concentration. Countries need to quantify their SOC stocks and flows in order to assess their greenhouse gas emissions. To facilitate this, the Intergovernmental Panel on Climate Change has developed a simple carbon accounting method to estimate SOC stocks and flows in response to changes in land use. This method proposes three tiers for SOC change estimation. The higher the tier the greater the accuracy of the estimates, but also the complexity and the need of information. We used the RothC model to derive SOC change factors in order to develop a Tier 2 (T2) method. We applied this T2 and Tier 1 (T1) methods to estimate SOC stocks and flows in five sub regions of the Argentinean Pampa Region between 1900 and 2006. We evaluated T1 and T2 methods performances comparing their estimates against empirical data, at sub region and county scales. At both spatial scales, T1 method showed a poor performance and an important improvement was achieved with T2 method, although its performance varied among spatial scales. At sub region scale, T2 method estimates were very good (R-2 = 0.85), but at county scale the fit was poor (R-2 = 0.46). However, this poor fit may have been due, at least in part, to the quality of the input and validation information of one of the sub regions (Flooding Pampa) since its exclusion of the analysis led to an increase of the R-2 up to 0.73. Tier 2 was used to estimate the impact of land use change on SOC. Sub regions with the highest estimated SOC losses were Central Pampa, Southern Pampa - Eastern and Rolling Pampa, with 35%, 28% and 26% average SOC losses, respectively. Given that several conceptual limitations of T1 method were overcome with our simple T2 method, we conclude that T2 method is more realistic to conduct a regional SOC inventory. Besides, our T2 method was developed without using empirical information from field or laboratory studies about SOC change and, therefore, countries that have not enough empirical information available on SOC change associated to land use could derive a similar T2 method. (C) 2014 Elsevier B.V. All rights reserved.
  • Authors:
    • Dias, G.
    • Wagner-Riddle, C.
    • Jayasundara, S.
    • Kariyapperuma, K.
  • Source: Canadian Journal of Soil Science
  • Volume: 94
  • Issue: 1
  • Year: 2014
  • Summary: Analysis of the environmental impact of corn (Zea mays L.) uses, such as biofuels and bioproducts, requires cradle to farm-gate life-cycle analysis of energy use and net greenhouse gas (GHG) emissions associated with corn production. Previous analyses have been based on case studies. Here we present an analysis based on census data for Ontario at the county level that was performed for three scenarios: (1) corn cultivated only for grain; (2) corn cultivated for grain and 30% stover harvest; and (3) corn cultivated for grain and cob harvest. Energy intensity of corn grain at the county level varied from 1.75 to 2.17 GJ Mg-1 grain, with the largest proportions of energy being consumed for grain drying (33%), production and supply of nitrogen (N) fertilizer (30%) and diesel use for field work (17%). Overall GHG emission intensity of grain corn varied from 243 to 353 kg CO(2)eq Mg-1 grain, of which 72% were associated with N inputs [34% soil nitrous oxide (N2O) from synthetic fertilizer N (SFN), 13% from SFN production and 10% from applied manure N]. Energy intensity of corn stover and cobs was 0.96 and 0.36 GJ Mg-1 dry matter, respectively, with the largest proportion of energy associated with production and supply of replacement nutrients. Intensity of GHG emission was 79 and 31 kg CO2 eq Mg-1 dry matter for stover and for cobs, respectively. Counties with higher corn yields at lower N application rates and reduced tillage tended to produce corn with lower energy and GHG intensity per Mg grain.
  • Authors:
    • Wienhold, B.
    • Schmer, M.
    • Venterea, R.
    • Varvel, G.
    • Stott, D.
    • Sauer, T.
    • Osborne, S.
    • Lehman, R.
    • Karlen, D.
    • Johnson, J.
    • Baker, J.
    • Jin, V.
  • Source: Bioenergy Research
  • Volume: 7
  • Issue: 2
  • Year: 2014
  • Summary: In-field measurements of direct soil greenhouse gas (GHG) emissions provide critical data for quantifying the net energy efficiency and economic feasibility of crop residue-based bioenergy production systems. A major challenge to such assessments has been the paucity of field studies addressing the effects of crop residue removal and associated best practices for soil management (i.e., conservation tillage) on soil emissions of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). This regional survey summarizes soil GHG emissions from nine maize production systems evaluating different levels of corn stover removal under conventional or conservation tillage management across the US Corn Belt. Cumulative growing season soil emissions of CO2, N2O, and/or CH4 were measured for 2-5 years (2008-2012) at these various sites using a standardized static vented chamber technique as part of the USDA-ARS's Resilient Economic Agricultural Practices (REAP) regional partnership. Cumulative soil GHG emissions during the growing season varied widely across sites, by management, and by year. Overall, corn stover removal decreased soil total CO2 and N2O emissions by -4 and -7 %, respectively, relative to no removal. No management treatments affected soil CH4 fluxes. When aggregated to total GHG emissions (Mg CO2 eq ha(-1)) across all sites and years, corn stover removal decreased growing season soil emissions by -5 +/- 1 % (mean +/- se) and ranged from -36 % to 54 % (n = 50). Lower GHG emissions in stover removal treatments were attributed to decreased C and N inputs into soils, as well as possible microclimatic differences associated with changes in soil cover. High levels of spatial and temporal variabilities in direct GHG emissions highlighted the importance of site-specific management and environmental conditions on the dynamics of GHG emissions from agricultural soils.
  • Authors:
    • Laird, D.
    • Brown, R.
    • Hayes, D.
    • Dumortier, J.
    • Kauffman, N.
  • Source: Biomass & Bioenergy
  • Volume: 63
  • Year: 2014
  • Summary: A partial solution to problems associated with anthropogenic greenhouse gas (GHG) emissions could be the development and deployment of carbon-negative technologies, i.e., producing energy while reducing atmospheric carbon dioxide levels. Biofuels have been considered a possibility but have faced limitations due to competition with food production and GHG emissions through indirect land-use change (ILUC). In this article, we show how emissions from ILUC can potentially be reduced by producing food and bioenergy from biochar amended soils. The possibility of yield improvements from biochar would reduce the land requirement for crop production and thus, lead to a reduction in emissions from ILUC. In our application, biochar and bio-oil are produced via fast pyrolysis of corn stover. ho-oil is subsequently upgraded into a fuel suitable for use in internal combustion engines. Applying the U.S. regulatory method used to determine biofuel life cycle emissions, our results show that a biochar-induced yield improvement in the U.S. Midwest ranging from 1% to 8% above trend can lead to an ILUC credit between 1.65 and 14.79 t CO2- equivalent ha(-1) year(-1) when future emissions are assessed over the next 30 years. The model is generalizable to other feedstocks and locations and illustrates the relationship between biochar and crop production. (C) 2014 Elsevier Ltd. All rights reserved.
  • Authors:
    • Keck, P.
    • Dale, B.
    • Kim, S.
  • Source: Bioenergy Research
  • Volume: 7
  • Issue: 2
  • Year: 2014
  • Summary: This meta-study quantitatively and qualitatively compares 21 published life cycle assessment (LCA)-type studies for energy consumption and greenhouse gas (GHG) emissions of maize production in the USA. Differences between the methodologies and numerical results obtained are described. Nonrenewable energy consumption in maize production (from cradle-to-farm gate) ranges from 1.44 to 3.50 MJ/kg of maize, and GHG emissions associated with maize production range from -27 to 436 g CO2 equivalent/kg of maize. Large variations between studies exist within the input data for lime application, fuels purchased, and life cycle inventory data for fertilizer and agrochemical production. Although most studies use similar methodological approaches, major differences between studies include the following: (1) impacts associated with human labor and farm machinery production, (2) changes in carbon dioxide emissions resulting from soil organic carbon levels, and (3) indirect N2O emissions.
  • Authors:
    • Hermansen, J. E.
    • Chirinda, N.
    • Olesen, J. E.
    • Meyer-Aurich, A.
    • Knudsen, M. T.
  • Source: Journal of Cleaner Production
  • Volume: 64
  • Issue: February
  • Year: 2014
  • Summary: Many current organic arable agriculture systems are challenged by a dependency on imported livestock manure from conventional agriculture. At the same time organic agriculture aims at being climate friendly. A life cycle assessment is used in this paper to compare the carbon footprints of different organic arable crop rotations with different sources of N supply. Data from long-term field experiments at three different locations in Denmark were used to analyse three different organic cropping systems ('Slurry', 'Biogas' and 'Mulching'), one conventional cropping system ('Conventional') and a "No input" system as reference systems. The 'Slurry' and 'Conventional' rotations received slurry and mineral fertilizer, respectively, whereas the 'No input' was unfertilized. The 'Mulching' and 'Biogas' rotations had one year of grass-clover instead of a faba bean crop. The grass-clover biomass was incorporated in the soil in the 'Mulching' rotation and removed and used for biogas production in the 'Biogas' rotation (and residues from biogas production were simulated to be returned to the field). A method was suggested for allocating effects of fertility building crops in life cycle assessments. The results showed significantly lower carbon footprint of the crops from the 'Biogas' rotation (assuming that biogas replaces fossil gas) whereas the remaining crop rotations had comparable carbon footprints per kg cash crop. The study showed considerable contributions caused by the green manure crop (grass-clover) and highlights the importance of analysing the whole crop rotation and including soil carbon changes when estimating carbon footprints of organic crops especially where green manure crops are included. (C) 2013 Elsevier Ltd. All rights reserved.
  • Authors:
    • Andren, O.
    • Zhao, X.
    • Luo, Y.
  • Source: Acta Agriculturae Scandinavica Section B-Soil and Plant Science
  • Volume: 64
  • Issue: 3
  • Year: 2014
  • Summary: Soil organic carbon (SOC) is a major source/sink in atmospheric carbon balances. Farmland usually has a high potential for carbon dioxide (CO2) uptake from the atmosphere, but also for emission. Data from different areas are valuable for global SOC calculations and model development, and a survey of 108 agricultural fields in Lanzhou, China was performed. The fields were grouped by: cropping intensity (3 levels), cropping methodology (3), and crop species (10). Intensive cropping (two or more crops per year, typically vegetables), moderate (annuals in monoculture: wheat, maize, potato, melons), and extensive (orchards, lily [Lilium brownii] fields, fallow) were the intensity classes; and open field, greenhouse field, and sand-covered field (10-20 cm added on top of the topsoil) were the three methodologies. SOC concentration, pH, electrical conductivity, and soil bulk density were measured, and SOC mass (gm(-2) 0-20 cm depth) was calculated. SOC concentration was high in cauliflower, wheat, leaf vegetables, and fruit vegetables; moderate in potato, fallow (3-5 years), tree orchards, and melons; while low in lily and maize fields, and differences in SOC mass followed the same pattern. SOC concentration and mass were lowest in the extensive fields while moderate and intensive fields showed higher values. Soil bulk density in open fields was significantly lower than those in greenhouse and sand-covered fields. The climate-induced soil activity factor r(e_clim) was calculated, compared with European conditions, and was fairly similar to those in central Sweden. Other factors behind the measured results, such as the influence of initial SOC content, manure addition, crops, etc., are discussed.