• Authors:
    • Kim, J.
    • Guillaume, B.
    • Laratte, B.
    • Birregah, B.
  • Source: Science of the Total Environment
  • Volume: 481
  • Year: 2014
  • Summary: This paper aims at presenting a dynamic indicator for life cycle assessment (LCA) measuring cumulative impacts over time of greenhouse gas (GHG) emissions from fertilizers used for wheat cultivation and production. Our approach offers a dynamic indicator of global warming potential (GWP), one of the most used indicator of environmental impacts (e.g. in the Kyoto Protocol). For a case study, the wheat production in France was selected and considered by using data from official sources about fertilizer consumption and production of wheat We propose to assess GWP environmental impact based on LCA method. The system boundary is limited to the fertilizer production for 1 ton of wheat produced (functional unit) from 1910 to 2010. As applied to wheat production in France, traditional LCA shows a maximum GWP impact of 500 kg CO2-eg for 1 ton of wheat production, whereas the GWP impact of wheat production over time with our approach to dynamic LCA and its cumulative effects increases to 18,000 kg CO2-eg for 1 ton of wheat production. In this paper, only one substance and one impact assessment indicator are presented. However, the methodology can be generalized and improved by using different substances and indicators. (C) 2014 Elsevier B.V. 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.
  • Authors:
    • McGree, J.
    • Bell, M.
    • Rowlings, D.
    • Grace, P.
    • Scheer, C.
    • Migliorati, M.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 186
  • Year: 2014
  • Summary: Global cereal production will need to increase by 50% to 70% to feed a world population of about 9 billion by 2050. This intensification is forecast to occur mostly in subtropical regions, where warm and humid conditions can promote high N2O losses from cropped soils. To secure high crop production without exacerbating N20 emissions, new nitrogen (N) fertiliser management strategies are necessary. This one-year study evaluated the efficacy of a nitrification inhibitor (3,4-dimethylpyrazole phosphate DMPP) and different N fertiliser rates to reduce N2O emissions in a wheat-maize rotation in subtropical Australia. Annual N2O emissions were monitored using a fully automated greenhouse gas measuring system. Four treatments were fertilized with different rates of urea, including a control (40 kg-N ha(-1) year(-1)), a conventional N fertiliser rate adjusted on estimated residual soil N (120 kg-N ha-1 year-1), a conventional N fertiliser rate (240 kg-N ha-1 year-1) and a conventional N fertiliser rate (240 kg-N ha-1 year-1) with nitrification inhibitor (DMPP) applied at top dressing. The maize season was by far the main contributor to annual N2O emissions due to the high soil moisture and temperature conditions, as well as the elevated N rates applied. Annual N2O emissions in the four treatments aMounted to 0.49, 0.84, 2.02 and 0.74 kg N2O N ha-1 year-1, respectively, and corresponded to emission factors of 0.29%, 0.39%, 0.69% and 0.16% of total N applied. Halving the annual conventional N fertiliser rate in the adjusted N treatment led to N2O emissions comparable to the DMPP treatment but extensively penalised maize yield. The application of DMPP produced a significant reduction in N2O emissions only in the maize season. The use of DMPP with urea at the conventional N rate reduced annual N2O emissions by more than 60% but did not affect crop yields. The results of this study indicate that: (i) future strategies aimed at securing subtropical cereal production without increasing N2O emissions should focus on the fertilisation of the summer crop; (ii) adjusting conventional N fertiliser rates on estimated residual soil N is an effective practice to reduce N2O emissions but can lead to substantial yield losses if the residual soil N is not assessed correctly; (iii) the application of DMPP is a feasible strategy to reduce annual N2O emissions from sub-tropical wheat-maize rotations. However, at the N rates tested in this study DMPP urea did not increase crop yields, making it impossible to recoup extra costs associated with this fertiliser. The findings of this study will support farmers and policy makers to define effective fertilisation strategies to reduce N2O emissions from subtropical cereal cropping systems while maintaining high crop productivity. More research is needed to assess the use of DMPP urea in terms of reducing conventional N fertiliser rates and subsequently enable a decrease of fertilisation costs and a further abatement of fertiliser-induced N2O emissions. (c) 2014 Elsevier B.V. All rights reserved.
  • Authors:
    • Robertson, R. D.
    • Mueller, C.
  • Source: Agricultural Economics
  • Volume: 45
  • Issue: 1
  • Year: 2014
  • Summary: Assessments of climate change impacts on agricultural markets and land-use patterns rely on quantification of climate change impacts on the spatial patterns of land productivity. We supply a set of climate impact scenarios on agricultural land productivity derived from two climate models and two biophysical crop growth models to account for some of the uncertainty inherent in climate and impact models. Aggregation in space and time leads to information losses that can determine climate change impacts on agricultural markets and land-use patterns because often aggregation is across steep gradients from low to high impacts or from increases to decreases. The four climate change impact scenarios supplied here were designed to represent the most significant impacts (high emission scenario only, assumed ineffectiveness of carbon dioxide fertilization on agricultural yields, no adjustments in management) but are consistent with the assumption that changes in agricultural practices are covered in the economic models. Globally, production of individual crops decrease by 10-38% under these climate change scenarios, with large uncertainties in spatial patterns that are determined by both the uncertainty in climate projections and the choice of impact model. This uncertainty in climate impact on crop productivity needs to be considered by economic assessments of climate change.
  • Authors:
    • Mukherjee, A.
    • Lal, R.
  • Source: Soil Research
  • Volume: 52
  • Issue: 3
  • Year: 2014
  • Summary: Any strategy towards widespread adoption of biochar as a soil amendment is constrained by the scarcity of field-scale data on crop response, soil quality and environmental footprint. Impacts of biochar as a soil amendment over a short period based on laboratory and greenhouse studies are often inconclusive and contradictory. Yet biochar is widely advocated as a promising tool to improve soil quality, enhance C sequestration, and increase agronomic yield. While substantial reviews exist on positive aspects of biochar research, almost no review to date has compiled negative aspects of it. Although biochar science is advancing, available data indicate several areas of uncertainty. This article reviews a range of negative impacts of biochar on soil quality, crop yield, and associated financial risk. This review is important because advances in biochar research demand identification of the risks (if any) of using biochar as a soil amendment before any large-scale field application is recommended. It is the first attempt to acknowledge such issues with biochar application in soil. Thus, the aims of this review are to assess the uncertainties of using biochar as a soil amendment, and to clarify ambiguity regarding interpretation of research results. Along with several unfavourable changes in soil chemical, physical and biological properties, reduction in crop yield has been reported. Relative to controls, the yield for biochar-amended soil (application rate 0.2-20% w/w) has been reduced by 27, 11, 36, 74, and 2% for rice (Oryza sativa L.) (control 3.0 Mg ha(-1)), wheat (Triticum spp. L.) (control 4.6 Mg ha(-1)), maize (Zea mays L.) (control 4.7 Mg ha(-1)), lettuce (Lactuca sativa L.) (control 5.4 Mg ha(-1)), and tomato (Solanum lycopersicum L.) (control 265 Mg ha(-1)), respectively. Additionally, compared with unamended soils, gaseous emissions from biochar-amended soils (application rate 0.005-10% w/w) have been enhanced up to 61, 152 and 14% for CO2 (control 9.7 Mg ha(-1) year(-1)), CH4 (control 222 kg ha(-1) year(-1)), and N2O (control 4.3 kg ha(-1) year(-1)), respectively. Although biochar has the potential to mitigate several environmental problems, the data collated herein indicate that a systematic road-map for manufacturing classification of biochars, and cost-benefit analysis, must be developed before implementation of field-scale application.
  • Authors:
    • Chand, S.
    • Patra, D. D.
    • Anwar, M.
  • Source: Journal of Environmental Management
  • Volume: 135
  • Issue: March
  • Year: 2014
  • Summary: organic carbon (SOC) is accumulated or depleted as a result of cropping and management strategies. It plays a significant role in maintaining soil quality, plant productivity and mitigating greenhouse gas emission. We studied the long-term (20 years) influence of a wheat-mint-Sesbania cropping system on the SOC stock. Estimates of stabilization of SOC in different pools and a tentative C budget were also developed. Twenty years of cultivation caused a decrease in SOC only in control soils, which received no manure and fertilizer. However, it increased with balanced use of NPK inputs. Soil C stock decreased significantly with increased in soil depth 0-15 cm to 15-30 and 30-45 cm. About 6% (-2 to+14) of the C added in crop residues and green manure were stabilized in the soil. On an average 12%, 14%, 59%, 15% of the water stable aggregates were in the >2 mm, 2.0-0.25 mm, 0.25-0.05 mm, and <0-0.5 size fractions, respectively. Significant improvements in structural stability and nitrogen availability were detected in all the treatments compared to the control. The amount of organic C oxidizable by a modified Walkley and Black method, which involves using only half of the amount of sulphuric acid, is a more sensitive indicator of the improvement in soil quality parameters under investigation, namely SOC, and increases in mineralizable N and water stable aggregation than the standard method. (c) 2014 Published by Elsevier Ltd.
  • Authors:
    • Horwath, W. R.
    • Zhu, X.
    • You, M.
    • Han, X.
    • Miao, S.
    • Qiao, Y.
  • Source: Field Crops Research
  • Volume: 161
  • Year: 2014
  • Summary: Long-term agronomic studies are useful to determine cropping system nitrogen (N) use efficiency and the fate of applied fertilizers. We used a subtractive fertilizer experiment incorporating N, phosphorous (P), potassium (K) and swine manure to determine long-term changes in grain yield, soil organic carbon (SOC), total soil nitrogen (N), as well as carbon dioxide (CO2) and nitrous oxide (N2O) emissions. The experiment was conducted on a 22-year maize-soybean-wheat rotation in Northeastern China. Crop residues were removed for cooking fuel and forage according to local practices. Five fertilizer treatments were applied annually: control (no fertilizer), NK, NP, NPK, and NPKOM (N, P. K and manure). The NPKOM treatment increased SOC and total soil N by 4.59 and 0.45 Mg ha(-1), respectively. In contrast, SOC decreased by 10.6 and 6.64 Mg ha(-1) in the control and NK treatments, respectively. The NPKOM treatment had an average of 2.9 times more N2O emissions than the other fertilizer treatments. The cropping system balances for N and SOC, together with fuel use for farming practices and manure handling, were used to calculate the global warming potential (GWP) of the different fertilizer treatments. Due to SOC sequestration, the GWP of the NPKOM treatment (6.77 Mg C equivalent ha(-1)) was significantly lower than that of both the control (14.4 Mg C equivalent ha(-1)) and the NK treatment (12.8 Mg C equivalent ha(-1)). The results suggest that in rainfed agricultural systems in Northeastern China, the application of manure supplemented with NPK can simultaneously achieve higher grain yield and lower GWP compared to mineral fertilizers alone.
  • Authors:
    • McDonald, A. J.
    • Bishnoi, D. K.
    • Kumar, A.
    • Jat, M. L.
    • Majumdar, K.
    • Sapkota, T. B.
    • Pampolino, M.
  • Source: Field Crops Research
  • Volume: 155
  • Year: 2014
  • Summary: In the high-yielding wheat production systems in Northwest (NW) Indo-Gangetic Plains of India, intensive tillage operations and blanket fertilizer recommendations have led to high production costs, decreased nutrient use efficiency, lower profits and significant environmental externalities. No-tillage (NT) has been increasingly adopted in this region to reduce costs and increase input use efficiency. But, optimal nutrient management practices for NT based wheat production are still poorly understood. Opportunities exist to further enhance the yield, profitability, and resource use efficiency of NT wheat through site-specific nutrient management (SSNM). On-farm trials were conducted in seven districts of Haryana, India for two consecutive years (2010-11 and 2011-12) to evaluate three different approaches to SSNM based on recommendations from the Nutrient Expert (R) (NE) decision support system in NT and conventional tillage (CT) based wheat production systems. Performance of NE based recommendations was evaluated against current state recommendations and farmers' practices for nutrient management. Three SSNM treatments based on NE based recommendation were (1) 'NE80:20' with 80% N applied at planting and 20% at second irrigation (2) 'NE33:33:33' with N split as 33% basal, 33% at Crown Root Initiation (CRI) and 33% at second irrigation; and (3) 'NE80:GS' with N split as 80% basal and further application of N based on optical sensor (Green Seeker (TM))-guided recommendations. Yield, nutrient use efficiency and economic profitability were determined following standard agronomic and economic measurements and calculations. Cool Farm Tool (CET), an empirical model to estimate greenhouse gases (GHGs) from agriculture production, was used to estimate GHG emissions under different treatments. Wheat grain and biomass yield were higher under NT in 2010-11 but no difference was observed in 2011-12. The three NE-based nutrient management strategies increased yield, nutrient use efficiency as well as net return as compared to state recommendation and farmers' fertilization practice. Global warming potential (GWP) of wheat production was also lower with NT system as compared to CT system and NE-based nutrient managements as compared to farmers' fertilization practice. State recommended nutrient management had similar GWP as NE-based nutrient managements except NE80:GS in which GWP was the lowest. Results suggest that no-tillage system along with site-specific approaches for nutrient management can increase yield, nutrient use efficiency and profitability while decreasing GHG from wheat production in NW India.
  • Authors:
    • Dalgaard, R.
    • Petersen, B. M.
    • Oudshoorn, F. W.
    • Halberg, N.
    • Sorensen, C. G.
  • Source: Biosystems Engineering
  • Volume: 120
  • Issue: April
  • Year: 2014
  • Summary: Different tillage systems result in different resource uses and environmental impacts. Reduced tillage generates savings in direct energy input and the amount of machinery items needed. As the basics for holistic Life Cycle Assessments, both the influencing direct and indirect energy as sources of greenhouse gas emissions are required. Life Cycle inventories (LCI) were aggregated for a number of optimised machinery systems and tillage scenarios integrating a four crop rotation consisting of spring barley, winter barley, winter wheat and winter rape seed. By applying Life Cycle Assessments to a number of tillage scenarios and whole field operations sequences, the energy efficiency and environmental impact in terms of greenhouse gas emissions (GHG) were evaluated. Results showed that the total energy input was reduced by 26% for the reduced tillage system and by 41% for the no-tillage system. Energy used for traction and machine construction contributed between 6 and 8% of the total GHG emission per kg product. The total emission of GHG was 915 g CO2 equivalents per kg product by using the conventional tillage system, 817 g CO2 equivalents for the reduced tillage system and 855 g CO2 equivalents for the no tillage system. The no tillage system was expected to yield 10% less. The mineralisation in the soil contributed the most (50-60%) to this emission, while the fertiliser production contributed with 28-33%. The results stress the importance of applying a systems approach to capture the implications of, for example, sustained yields as otherwise the environmental benefits can be compromised. (C) 2014 IAgrE. Published by Elsevier Ltd. All rights reserved.
  • Authors:
    • Wynn, S. C.
    • Kindred, D. R.
    • Sylvester-Bradley, R.
    • Thorman, R. E.
    • Smith, K. E.
  • Source: The Journal of Agricultural Science
  • Volume: 152
  • Issue: 1
  • Year: 2014
  • Summary: Fertilizer nitrogen (N) accounts for the majority of the greenhouse gas (GHG) emissions associated with intensive wheat production, and the form of fertilizer N affects these emissions. Differences in manufacturing emissions (as represented in the current carbon accounting methodologies) tend to favour urea, even when using the best available manufacturing technologies (BAT), whereas differences in fertilizer N efficiency and emissions of ammonia tend to favour ammonium nitrate (AN). To resolve these differences, data from 47 experiments in two large UK studies conducted from 1982 to 1987 and from 2003 to 2005 were reanalysed, showing that on average urea efficiency was 0 center dot 9 of AN (although mean ammonia emissions in 10 subsidiary experiments indicated an efficiency difference of 0 center dot 2); treating urea with a urease inhibitor (TU; AGROTAIN((R)), active ingredient N-(n-butyl) thiophosphoric triamide (n-BTPT)) brought its efficiency almost in line with AN; however, a significantly greater mean optimum N amount for TU (+0 center dot 1 of AN) was not fully explained. A standard response function relating wheat yield to applied AN was modified for degrees of relative inefficiency, thus enabling yields and GHG intensities (kg CO(2)e/tonne (t) grain) to be calculated using a PAS2050 compatible model for GHG emissions for any N amount of any N form. With AN manufactured by average European technology (AET), the estimated GHG intensity of wheat producing 8 t/ha was 451 kg/t; whereas with urea or TU made by AET it was 0.87-0.99 or 0.84-0.86 of this respectively. Using BAT for fertilizer manufacture, the grain's GHG intensity with AN and TU was 368kg/t, but was 1 center dot 03-1 center dot 17 of this with untreated urea. The range of effects on GHG intensities arose mainly from remaining uncertainties in the inefficiencies of the N forms. Generally, economic margins and GHG intensities were not much affected by adjustments in N use for relative inefficiencies or different prices of urea-based fertilizers compared with AN. Overall, TU appeared to provide the best combination of economic performance and GHG intensity, unless the price for N as TU exceeded that for N as AN.