• Authors:
    • Osborne, B.
    • Richards, M.
    • Khalil, M. I.
    • Williams, M.
    • Mueller, C.
  • Source: Atmospheric Environment
  • Volume: 81
  • Issue: December
  • Year: 2013
  • Summary: Model simulations of C and N dynamics, based on country-specific agricultural and environmental conditions, can provide information for compiling national greenhouse gas (GHG) inventories, as well as insights into potential mitigation options. A multi-pool dynamic model, `ECOSSE' (v5 modified), was used to simulate coupled GHGs and soil organic carbon (SOC) stock changes. It was run for an equivalent time frame of 8 years with inputs from conventionally-tilled arable land cropped with spring barley receiving N fertilizer as calcium ammonium nitrate at 135-159 kg N ha(-1) and crop residues (3 t ha-1 yr-1). The simulated daily N2O fluxes were consistent with the measured values, with R-2 of 033 (p < 0.05) and the total error and bias differences were within 95% confidence levels. The measured seasonal N2O losses were 0.39-0.60% of the N applied, with a modelled estimate of 0.23-0.41%. In contrast, the measured annual N2O loss (integrated) was 0.35% and the corresponding simulated value of 0.45% increased to 0.59% when the sum of the daily fluxes was taken into account. This indicates intermittent gas samplings may miss the peak fluxes. On an 8-year average the modelled N2O emission factor (EF) was 0.53 0.03%. The model successfully predicted the daily heterotrophic respiration (RH), with an R-2 of 0.45 (p <0.05) and the total error and bias differences were within the 95% confidence intervals. The simulated and measured total RH (3149 versus 3072 kg C ha(-1) yr(-1)) was within the cropland average values previously reported. The total measured CH4 fluxes indicated that the unfertilized treatments were a small source (-2.29 g C ha(-1) yr(-1)), whilst the fertilized treatments were a sink (+3.64). In contrast, the simulated values suggested a sink (26.61-31.37 g C ha(-1) yr(-1)), demonstrating fertilizer-induced decreases in CH4 oxidation. On average, based on the simulated SOC content a loss of 516 kg C ha(-1) yr(-1) was indicated, which is within the uncertainty range for temperate regions. Results suggest that the model is suitable for estimating the GHG balance of arable fields. However, further refinements and analyses to fully determine and narrow down the uncertainty ranges for GHG estimates are required. (C) 2013 Elsevier Ltd. All rights reserved.
  • Authors:
    • Giltrap, D.
    • Hernandez-Ramirez, G.
    • Kim, D.-G.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 168
  • Issue: March
  • Year: 2013
  • Summary: Rising atmospheric concentrations of nitrous oxide (N2O) contribute to global warming and associated climate change. It is often assumed that there is a linear relationship between nitrogen (N) input and direct N2O emission in managed ecosystems and, therefore, direct N2O emission for national greenhouse gas inventories use constant emission factors (EF). However, a growing body of studies shows that increases in direct N2O emission are related by a nonlinear relationship to increasing N input. We examined the dependency of direct N2O emission on N input using 26 published datasets where at least four different levels of N input had been applied. In 18 of these datasets the relationship of direct N2O emission to N input was nonlinear (exponential or hyperbolic) while the relationship was linear in four datasets. We also found that direct N2O EF remains constant or increases or decreases nonlinearly with changing N input. Studies show that direct N2O emissions increase abruptly at N input rates above plant uptake capacity. The remaining surplus N could serve as source of additional N2O production, and also indirectly promote N2O production by inhibiting biochemical N2O reduction. Accordingly, we propose a hypothetical relationship to conceptually describe in three steps the response of direct N2O emissions to increasing N input rates: (1) linear (N limited soil condition), (2) exponential, and (3) steady-state (carbon (C) limited soil condition). In this study, due to the limited availability of data, it was not possible to assess these hypothetical explanations fully. We recommend further comprehensive experimental examination and simulation using process-based models be conducted to address the issues reported in this review. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Thakur, K. P.
    • Tate, K. R.
    • Saggar, S.
    • Kirschbaum, M. U. F.
    • Giltrap, D. L.
  • Source: Science of The Total Environment
  • Volume: 465
  • Issue: November
  • Year: 2013
  • Summary: Land-use change between forestry and agriculture can cause large net emissions of carbon dioxide (CO2), and the respective land uses associated with forest and pasture lead to different on-going emission rates of methane (CH4) and nitrous oxide (N2O) and different surface albedo. Here, we quantify the overall net radiative forcing and consequent temperature change from specified land-use changes. These different radiative agents cause radiative forcing of different magnitudes and with different time profiles. Carbon emission can be very high when forests are cleared. Upon reforestation, the former carbon stocks can be regained, but the rate of carbon sequestration is much slower than the rate of carbon loss from deforestation. A production forest may undergo repeated harvest and regrowth cycles, each involving periods of C emission and release. Agricultural land, especially grazed pastures, have much higher N2O emissions than forests because of their generally higher nitrogen status that can be further enhanced through intensification of the nitrogen cycle by animal excreta. Because of its longevity in the atmosphere, N2O concentrations build up nearly linearly over many decades. CH4 emissions can be very high from ruminant animals grazing on pastures. Because of its short atmospheric longevity, the CH4 concentration from a converted pasture accumulates for only a few decades before reaching a new equilibrium when emission of newly produced CH4 is balanced by the oxidation of previously emitted CH4. Albedo changes generally have the opposite radiative forcing from those of the GHGs and partly negate their radiative forcing. Overall and averaged over 100 years, CO2 is typically responsible for 50% of radiative forcing and CH4 and N2O for 25% each. Albedo changes can negate the radiative forcing by the three greenhouse gases by 20-25%. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Bonsch, M.
    • Dietrich, J. P.
    • Popp, A.
    • Lotze-Campen, H.
    • Krause, M.
  • Source: Land Use Policy
  • Volume: 30
  • Issue: 1
  • Year: 2013
  • Summary: Conservation of undisturbed natural forests, which are important for biodiversity, carbon storage, and other ecosystem services, affects agricultural production and cropland expansion. We analyze the economic impacts of undisturbed natural forest conservation programs on agriculture and the magnitude of avoided deforestation and avoided carbon emissions in the tropics. We apply a global agricultural land use model to estimate changes in agricultural production costs for the period 2015-2055. Our forest conservation scenarios reflect two different policy goals: either maximize forest carbon storage or minimize impacts on agricultural production. In all the scenarios, the economic impacts on agriculture are relatively low. Production costs would increase due to forest conservation by a maximum of 4%, predominantly driven by increased investments in agricultural productivity increase. We also show regional differences in Latin America, Sub-Saharan Africa, and Southeast Asia, due to different growth rates in food demand, land availability and crop productivity. The area of avoided deforestation does not exceed 1.5 million ha yr(-1) in the period 2015-2055, while avoided carbon emissions reach a maximum of 1.9 Gt CO2 per year. According to our results on the potential changes in agricultural production costs, undisturbed natural forest conservation appears to be a low-cost option for greenhouse gas emission reduction. (C) 2012 Elsevier Ltd. All rights reserved.
  • Authors:
    • Huelsbergen, K.-J.
    • Munch, J. C.
    • Kuestermann, B.
  • Source: European Journal of Agronomy
  • Volume: 49
  • Issue: August
  • Year: 2013
  • Summary: Two factorial long-term field experiments were carried out at the experimental site of Scheyern, located in southern Germany, 40 km north of Munich (48 degrees 30'0' N, 11 degrees 26'60' E). Here three soil tillage systems were investigated: CT (conventional tillage with moldboard plough, 25 cm plowing depth), RT1 (reduced tillage with chisel plow, 18 cm working depth), and RT2 (reduced tillage with chisel plow, 8 cm working depth). At the same time, three fertilization systems were analyzed (high (N3), medium (N2) and low (N1) mineral N input) with a crop rotation of winter wheat (Triticum aestivum L) - potatoes (Solanum tuberosum L.) - winter wheat-corn (Zea mays L). The long-term effects of tillage and fertilization on yields, soil properties, nitrogen and energy efficiency, as well as greenhouse gas emissions (GGE) were investigated for the period of 1994-2005. On average conventional tillage (CT) produced yields of 8.03 (N1), 8.82 (N2) and 8.88 (N3) GE (grain equivalents) ha(-1) yr(-1); reduced tillage (RT1) yields of 7.82 (N1), 8.54 (N2) and 9.10 (N3) GE ha(-1) yr(-1) and RT2 yields of 6.9 (Ni), 7.82 (N2) and 8.6 (N3) GE ha(-1) yr(-1). The benefit of reduced soil tillage over CT. is a lower consumption of diesel fuel (reduced by 35%) and fossil energy (by 10%), C sequestration and N accumulation in soil. We recorded the highest soil organic carbon (SOC) in the RT2 treatments with the lowest tillage intensity (52.5 Mg ha(-1)) and the lowest SOC reserves in the CT plowed treatments (41.1 Mg ha(-1)). During the reported period, SOC reserves in the plowed treatments decreased by about 300 kg C ha-1 yr-1, whereas they increased by 150-500 kg C ha(-1) yr(-1) in the chiseled treatments. Similar results were achieved with the soil organic nitrogen (SON) reserves based on the type of tillage. This amounted to around 4000 kg ha-1 (CT), 4500 kg ha (RT1) and more than 5000 kg N ha-1 (RT2). The RT1 treatments were marked by high nutrient and energy efficiency. The disadvantage of reduced tillage lies in higher pesticide consumption and stronger soil compaction. The influence of reduced tillage was more pronounced in RT2 than in RT1 (higher SOC and SON content, higher soil dry bulk density, lower consumption of diesel fuel, higher pesticide input). The significant decreases in yield in the RT2 treatments reduced the nitrogen and energy efficiency and raised yield-related greenhouse gas emissions (GGE) in comparison to the RT1 treatments. In the case of reduced tillage combined with high N doses (RT1/N3, RT2/N2, RT2/N3), high N2O emissions of 10 to 12 kg ha(-1) yr(-1) were measured using closed chambers. It was found that as input of mineral N increased, GGE for tillage treatments, both area and yield related also increased. In RT1/N1, negative net GGE were recorded due to high C sequestration combined with moderate N2O and CO2 emissions (-220 kg CO2 (eq) ha(-1) yr(-1), -28 kg CO2 eq GE-(1)), whereas CT/N3 produced the highest net GGE (3587 kg CO2 (eq) ha(-1) yr(-1), 404 kg CO2 eq GE(-1)). (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Chatterton, J.
    • Graves, A.
    • Kulak, M.
  • Source: Landscape and Urban Planning
  • Volume: 111
  • Issue: March
  • Year: 2013
  • Summary: The production and supply of food currently accounts for 20-30% of greenhouse gas (GHG) emissions in the UK and the government and nongovernmental organisations are seeking to reduce these environmental burdens. Local authorities all over UK establish community farms with the aim to produce more sustainable food for citizens. This study used environmental Life Cycle Assessment (LCA) to quantify the potential savings of food-related GHG emissions that may be achieved with the establishment of an urban community farm, based on a case study recently found in the London Borough of Sutton. The work identified elements of the farm design that require the greatest attention to maximise these savings. The greatest reductions can be achieved by selecting the right crops: (i) providing the highest yields in local conditions and (ii) usually produced in energy-intensive greenhouses or air-freighted to UK from outside Europe. Implications from further development of the farm on the local, unused land were examined, taking into account market requirements. This showed that land used on an urban fringe for food production could potentially reduce greenhouse gas emissions in Sutton by up to 34 t CO(2)e ha(-1) a(-1). Although the percentage of this reduction in total diet emissions is relatively low, the result exceeds carbon sequestration rates for the conventional urban green space projects, such as parks and forests. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Armstrong, R.
    • Norton, R.
    • Chen, D.
    • Lam, S. K.
    • Mosier, A. R.
  • Source: The Journal of Agricultural Science
  • Volume: 151
  • Issue: 2
  • Year: 2013
  • Summary: The effect of elevated carbon dioxide (CO2) concentration on greenhouse gas (GHG) emission from semi-arid cropping systems is poorly understood. Closed static chambers were used to measure the fluxes of nitrous oxide (N2O), CO2 and methane (CH4) from a spring wheat (Triticum aestivum L. cv. Yitpi) crop-soil system at the Australian grains free-air carbon dioxide enrichment (AGFACE) facility at Horsham in southern Australia in 2009. The targeted atmospheric CO2 concentrations (hereafter CO2 concentration is abbreviated as [CO2]) were 390 (ambient) and 550 (elevated) mu mol/mol for both rainfed and supplementary irrigated treatments. Gas measurements were conducted at five key growth stages of wheat. Elevated [CO2] increased the emission of N2O and CO2 by 108 and 29%, respectively, with changes being greater during the wheat vegetative stage. Supplementary irrigation reduced N2O emission by 36%, suggesting that N2O was reduced to N-2 in the denitrification process. Irrigation increased CO2 flux by 26% at ambient [CO2] but not at elevated [CO2], and had no impact on CH4 flux. The present results suggest that under future atmospheric [CO2], agricultural GHG emissions at the vegetative stage may be higher and irrigation is likely to reduce the emissions from semi-arid cropping systems.
  • Authors:
    • Mosier, A. R.
    • Chen, D.
    • Lam, S. K.
    • Roush, R.
  • Source: Scientific Reports
  • Volume: 3
  • Issue: July
  • Year: 2013
  • Summary: Concerns about increasing concentrations of greenhouse gases in the atmosphere, primarily carbon dioxide (CO2), have raised worldwide interest in the potential of agricultural soils to be carbon (C) sinks. In Australia, studies that have quantified the effects of improved management practices in croplands on soil C have generally been inconclusive and contradictory for different soil depths and durations of the management changes. We therefore quantitatively synthesised the results of Australian studies using meta-analytic techniques to assess the technical and economic feasibility of increasing the soil C stock by improved management practices. Our results indicate that the potential of these improved practices to store C is limited to the surface 0-10 cm of soil and diminishes with time. None of these widely adopted practices is currently financially attractive under Australia's new legislation known as the Carbon Farming Initiative.
  • Authors:
    • Ro, H.-M.
    • Lee, H.-C.
    • Kim, J.-S.
    • Choi, J.-J.
    • Lee, T.-K.
  • Source: Korean Journal of Horticultural Science & Technology
  • Volume: 31
  • Issue: 6
  • Year: 2013
  • Summary: To report country-specific carbon and nitrogen stocks data in a pear orchard by Tier 3 approach of 2006 IPCC guidelines for national greenhouse gas inventories, an experimental pear orchard field of the Pear Research Station, National Institute of Horticultural & Herbal Science, Rural Development Administration, Naju, Korea (35 01'27.70 N, 126 44'53.50"E, 6 m altitude), where 15-year-old `Niitaka' pear (Pyrus pyrifolia Nakai cv. Niitaka) trees were planted at a 5.0 m x 3.0 m spacing on a Tatura trellis system, was chosen to assess the total amount of carbon and nitrogen stocks stored in the trees and orchard soil profiles. At the sampling time (August 2012), three trees were uprooted, and separated into six fractions: trunk, main branches, lateral branches (including shoots), leaves, fruits, and roots. Soil samples were collected from 0 to 0.6 m depth at 0.1 m intervals at 0.5 m from the trunk. Dry mass per tree was 4.7 kg for trunk, 13.3 kg for main branches, 13.9 kg for lateral branches, 3.7 kg for leaves, 6.7 kg for fruits, and 14.1 kg for roots. Amounts of C and N per tree were respectively 2.3 and 0.02 kg for trunk, 6.4 and 0.07 kg for main branches, 6.4 and 0.09 kg for lateral branches, 6.5 and 0.07 kg for roots, 1.7 and 0.07 kg for leaves, and 3.2 and 0.03 kg for fruits. Carbon and nitrogen stocks stored between the soil surface and a depth of 60 cm were 138.29 and 13.31 Mg.ha(-1), respectively, while those contained in pear trees were 17.66 and 0.23 Mg ha' based on a tree density of 667 trees-ha-1.0verall, carbon and nitrogen stocks per hectare stored in a pear orchard were 155.95 and 13.54 Mg, respectively.
  • Authors:
    • Tzilivakis, J.
    • Warner, D. J.
    • Green, A.
    • Lewis, K. A.
  • Source: International Journal of Agricultural Sustainability
  • Volume: 11
  • Issue: 2
  • Year: 2013
  • Summary: The agricultural sector contributes 9% towards total UK greenhouse gas emissions and so may offer significant potential as a sector to help meet national and international emission reduction targets. In order to help farmers manage their emissions and to encourage more sustainable farming, several carbon accounting tools are now available. This article describes a short study that selected five suitable tools and compared their performance on nine European arable farms, concentrating on the crop production components, to determine how useful they are for assisting in the development of site-specific mitigation strategies and how well they would perform within farm assurance or benchmarking schemes. The results were mixed, with some tools better designed for identifying mitigation opportunities than others. The results also showed that, quantitatively, the results are highly variable between tools and depended on the selected functional unit, this being highly important if the wider aspects of sustainability such as food security are to be considered. However, there is statistical consistency across the tools regarding the ranking order of the farms in terms of their emissions.