• Authors:
    • Nolan, P.
    • Burke, J.
    • Roth, B.
    • Helmy, M.
    • Osborne, B.
    • Jones, M.
    • Rueangritsarakul, K.
    • Abdalla, M.
    • Smith, P.
    • Williams, M.
  • Source: Water, Air, & Soil Pollution
  • Volume: 223
  • Issue: 8
  • Year: 2012
  • Summary: Field management is expected to influence nitrous oxide (N2O) production from arable cropping systems through effects on soil physics and biology. Measurements of N2O flux were carried out on a weekly basis from April 2008 to August 2009 for a spring sown barley crop at Oak Park Research Centre, Carlow, Ireland. The soil was a free draining sandy loam typical of the majority of cereal growing land in Ireland. The aims of this study were to investigate the suitability of combining reduced tillage and a mustard cover crop (RT-CC) to mitigate nitrous oxide emissions from arable soils and to validate the DeNitrification-DeComposition (DNDC) model version (v. 9.2) for estimating N2O emissions. In addition, the model was used to simulate N2O emissions for two sets of future climate scenarios (period 2021-2060). Field results showed that although the daily emissions were significantly higher for RT-CC on two occasions (p 0.05) on the cumulative N2O flux, compared with the CT treatment, was found. DNDC was validated using N2O data collected from this study in combination with previously collected data and shown to be suitable for estimating N2O emissions (r (2) = 0.70), water-filled pore space (WFPS) (r (2) = 0.58) and soil temperature (r (2) = 0.87) from this field. The relative deviations of the simulated to the measured N2O values with the 140 kg N ha(-1) fertiliser application rate were -36 % for RT-CC and -19 % for CT. Root mean square error values were 0.014 and 0.007 kg N2O-N ha(-1) day(-1), respectively, indicating a reasonable fit. Future cumulative N2O fluxes and total denitrification were predicted to increase under the RT-CC management for all future climate projections, whilst predictions were inconsistent under the CT. Our study suggests that the use of RT-CC as an alternative farm management system for spring barley, if the sole objective is to reduce N2O emissions, may not be successful.
  • Authors:
    • Klakegg, O.
    • Janzen, H. H.
    • Skjelvag, A. O.
    • Bonesmo, H.
    • Tveito, O. E.
  • Source: Agricultural Systems
  • Volume: 110
  • Issue: July
  • Year: 2012
  • Summary: To increase food production while mitigating climate change, cropping systems in the future will need to reduce greenhouse gas emission per unit of production. We conducted an analysis of 95 arable farms in Norway to calculate farm scale emissions of greenhouse gases, expressed both as CO2 eq per unit area, and CO2 eq per kg DM produced and to describe relationships between the farms' GHG intensities and heir economic efficiencies (gross margin). The study included: (1) design of a farm scale model for net GHG emission from crop production systems; (2) establishing a consistent farm scale data set for the farms with required soil, weather, and farm operation data; (3) a stochastic simulation of the variation in the sources of GHG emission intensities, and sensitivity analysis of selected parameters and equations on GHG emission intensities; and (4) describing relationships between GHG emission intensities and gross margins on farms. Among small seed and grain crops the variation in GHG emissions per kg DM was highest in oilseed (emission intensity at the 75th percentile level was 1.9 times higher than at the 25th percentile). For barley, oats, spring wheat, and winter wheat, emissions per kg DM at the 75th percentile levels were between 1.4 and 1.6 times higher than those at the 25th percentiles. Similar trends were observed for emissions per unit land area. Invariably soil N2O emission was the largest source of GHG emissions, accounting for almost half of the emissions. The second largest source was the off farm manufacturing of inputs (similar to 25%). Except for the oilseed crop, in which soil carbon (C) change contributed least, the on farm emissions due to fuel use contributed least to the total GHG intensities (similar to 10%). The soil C change contributed most to the variability in GHG emission intensities among farms in all crops, and among the sensitivity elasticities the highest one was related to environmental impacts on soil C change. The high variation in GHG intensities evident in our study implies the potential for significant mitigation of GHG emissions. The GHG emissions per kg DM (intensity) decreased with increasing gross margin in grain and oilseed crops, suggesting that crop producers have economic incentives to reduce GHG emissions. (c) 2012 Elsevier Ltd. All rights reserved,
  • Authors:
    • Fitt, B. D. L.
    • Smith, P.
    • West, J. S.
    • Carlton, R. R.
  • Source: European Journal of Plant Pathology
  • Volume: 133
  • Issue: 1
  • Year: 2012
  • Summary: Crop disease not only threatens global food security by reducing crop production at a time of growing demand, but also contributes to greenhouse gas (GHG) emissions by reducing efficiency of N fertiliser use and farm operations and by driving land use change. GHG emissions associated with adoption of reduced tillage, organic and integrated systems of field crop production across the UK and selected regions are compared with emissions from conventional arable farming to assess their potential for climate change mitigation. The reduced tillage system demonstrated a modest (< 20%) reduction in emissions in all cases, although in practice it may not be suitable for all soils and it is likely to cause problems with control of diseases spread on crop debris. There were substantial increases in GHG emissions associated with the organic and integrated systems at national level, principally due to soil organic carbon losses from land use change. At a regional level the integrated system shows the potential to deliver significant emission reductions. These results indicate that the conventional crop production system, coupled to reduced tillage cultivation where appropriate, is generally the best for producing high yields to minimise greenhouse gas emissions and contribute to global food security, although there may be scope for use of the integrated system on a regional basis. The control of crop disease will continue to have an essential role in both maintaining productivity and decreasing GHG emissions.
  • Authors:
    • Schmidt, J. E.
    • Thomsen, S. T.
    • Jensen, M.
    • Heiske, S.
    • Hauggaard-Nielsen, H.
    • Carter, M. S.
    • Johansen, A.
    • Ambus, P.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 4
  • Year: 2012
  • Summary: One way of reducing the emissions of fossil fuel-derived carbon dioxide (CO2) is to replace fossil fuels with biofuels produced from agricultural biomasses or residuals. However, cultivation of soils results in emission of other greenhouse gases (GHGs), especially nitrous oxide (N2O). Previous studies on biofuel production systems showed that emissions of N2O may counterbalance a substantial part of the global warming reduction, which is achieved by fossil fuel displacement. In this study, we related measured field emissions of N2O to the reduction in fossil fuel-derived CO2, which was obtained when agricultural biomasses were used for biofuel production. The analysis included five organically managed feedstocks (viz. dried straw of sole cropped rye, sole cropped vetch and intercropped ryevetch, as well as fresh grassclover and whole crop maize) and three scenarios for conversion of biomass into biofuel. The scenarios were (i) bioethanol, (ii) biogas and (iii) coproduction of bioethanol and biogas. In the last scenario, the biomass was first used for bioethanol fermentation and subsequently the effluent from this process was utilized for biogas production. The net GHG reduction was calculated as the avoided fossil fuel-derived CO2, where the N2O emission was subtracted. This value did not account for fossil fuel-derived CO2 emissions from farm machinery and during conversion processes that turn biomass into biofuel. The greatest net GHG reduction, corresponding to 700800 g CO2 m(-2), was obtained by biogas production or coproduction of bioethanol and biogas on either fresh grassclover or whole crop maize. In contrast, biofuel production based on lignocellulosic crop residues (i.e. rye and vetch straw) provided considerably lower net GHG reductions (=215 g CO2 m(-2)), and even negative numbers sometimes. No GHG benefit was achieved by fertilizing the maize crop because the extra crop yield, and thereby increased biofuel production, was offset by enhanced N2O emissions.
  • Authors:
    • Grant, T.
    • Carre, A.
    • Eady, S.
  • Source: Journal of Cleaner Production
  • Volume: 28
  • Issue: June
  • Year: 2012
  • Summary: Most agricultural products are produced on farms where there is a mix of activities, resulting in a range of co-products. This raises the issue of how best to model these complex production systems for Life Cycle Assessment, especially where there are benefits imparted by one activity in the mixed farming system to another. On the mixed farm studied, there were significant two-way reference flows (representing 288 t CO2-e/year or 10% of the total farm emissions) between activities producing distinct products (wool, meat, grain) and these were modelled using system expansion. Cropping and sheep activities were modelled as separate sub-processes in the farming system, with unique inputs and outputs identified for each. Co-production from the sheep activity was modelling using allocation, comparing biophysical and economic relationships. Using an economic allocation resulted in different estimates of global warming impact for sheep co-products, with figures varying by 7-52%. When compared to biophysical allocation, economic allocation shifted the environmental burden to the higher value co-products and away from the high resource use products. Using economic allocation, for every kilogram of wool produced there was an estimated 28.7 kg of CO2-e emitted. Amongst the live animal products, the stud rams had the highest estimated carbon footprint (719 kg CO2-e/ram). Amongst the crops, estimates of emissions for the cereal grains averaged 202 kg CO2-e/tonne grain, canola 222 kg CO2-e/tonne and lupins 510 kg CO2-e/tonne, when modelled to include the benefits of the mixed farming system. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.
  • Authors:
    • Niu, J.
    • Malhi, S. S.
    • May, W.
    • Liang, C.
    • Gan, Y.
    • Wang, X.
  • Source: The International Journal of Life Cycle Assessment
  • Volume: 17
  • Issue: 5
  • Year: 2012
  • Summary: Carbon footprint of field crops can be lowered through improved cropping practices. The objective of this study was to determine the carbon footprint of spring barley ( L.) in relation to various preceding oilseed crops that were fertilized at various rates of inorganic N the previous years. System boundary was from cradle-to-farm gate. Canola-quality mustard ( L.), canola ( L.), sunflower ( L.), and flax ( L.) were grown under the N fertilizer rates of 10, 30, 70, 90, 110, 150, and 200 kg N ha(-1) the previous year, and spring barley was grown on the field of standing oilseed stubble the following year. The study was conducted at six environmental sites; they were at Indian Head in 2005, 2006 and 2007, and at Swift Current in 2004, 2005 and 2006, Saskatchewan, Canada. On average, barley grown at humid Indian Head emitted greenhouse gases (GHGs) of 1,003 kg CO(2)eq ha(-1), or 53% greater than that at the drier Swift Current site. Production and delivery of fertilizer N to farm gate accounted for 26% of the total GHG emissions, followed by direct and indirect emissions of 28% due to the application of N fertilizers to barley crop. Emissions due to N fertilization were 26.6 times the emission from the use of phosphorous, 5.2 times the emission from pesticides, and 4.2 times the emission from various farming operations. Decomposition of crop residues contributed emissions of 173 kg CO(2)eq ha(-1), or 19% of the total emission. Indian Head-produced barley had significantly greater grain yield, resulting in about 11% lower carbon footprint than Swift Current-produced barley (0.28 vs. 0.32 kg CO(2)eq kg(-1) of grain). Emissions in the barley production was a linear function of the rate of fertilizer N applied to the previous oilseed crops due to increased emissions from crop residue decomposition coupled with higher residual soil mineral N. The key to lower the carbon footprint of barley is to increase grain yield, make a wise choice of crop types, reduce N inputs to crops grown in the previous and current growing seasons, and improved N use efficiency.
  • Authors:
    • Williams, S.
    • Easter, M.
    • Paustian, K.
    • Lokupitiya, E.
    • Andren, O.
    • Katterer, T.
  • Source: Biogeochemistry
  • Volume: 107
  • Issue: 1-3
  • Year: 2012
  • Summary: Carbon (C) added to soil as organic matter in crop residues and carbon emitted to the atmosphere as CO(2) in soil respiration are key determinants of the C balance in cropland ecosystems. We used complete and comprehensive county-level yields and area data to estimate and analyze the spatial and temporal variability of regional and national scale residue C inputs, net primary productivity (NPP), and C stocks in US croplands from 1982 to 1997. Annual residue C inputs were highest in the North Central and Central and Northern Plains regions that comprise similar to 70% of US cropland. Average residue C inputs ranged from 1.8 (Delta States) to 3.0 (North Central region) Mg C ha(-1) year(-1), and average NPP ranged from 3.1 (Delta States) to 5.4 (Far West region) Mg C ha(-1) year(-1). Residue C inputs tended to be inversely proportional to the mean growing season temperature. A quadratic relationship incorporating the growing season mean temperature and total precipitation closely predicted the variation in residue C inputs in the North Central region and Central and Northern Plains. We analyzed the soil C balance using the crop residue database and the Introductory Carbon Balance regional Model (ICBMr). Soil C stocks (0-20 cm) on permanent cropland ranged between 3.07 and 3.1 Pg during the study period, with an average increase of similar to 4 Tg C year(-1), during the 1990s. Interannual variability in soil C stocks ranged from 0 to 20 Tg C (across a mean C stock of 3.08 +/- A 0.01 Pg) during the study period; interannual variability in residue C inputs varied between 1 and 43 Tg C (across a mean input of 220 +/- A 19 Tg). Such interannual variation has implications for national estimates of CO(2) emissions from cropland soils needed for implementation of greenhouse gas (GHG) mitigation strategies involving agriculture.
  • Authors:
    • Cockfield, G.
    • Maraseni, T. N.
  • Source: Agricultural Water Management
  • Volume: 103
  • Year: 2012
  • Summary: Irrigated cropping helps stabilise farm and regional income and contributes to productivity gains but the net benefits should include the full cost of water and greenhouse gas (GHG) emissions. This study examines the costs and returns of switching from a dryland rotation for four crops in the Darling Downs region of Australia, to a rotation of the same crops under irrigation, including greenhouse gas (GHG) values. The value chain, including all inputs was identified and emissions estimated using a range of studies and models. Over four year cropping cycle, the irrigated system would result in more than six times the emissions than from the dryland system. If GHG and water prices are not embedded in the production process, irrigation is more profitable per hectare. In this scenario, the landholder makes more than twice as much from the irrigated crops, with gross margins for the dryland and irrigated crop rotations of $1597 and $3490/ha, respectively. If the value of GHGs is included, the gap closes but irrigated crops are still more profitable. If however, a relatively high cost of the water, based on price ranges from the last decade, is included, then dryland crops are financially preferable. These results could be useful in designing national mitigation and water buy-back policies, both of which are being developed in Australia.
  • Authors:
    • Ward, P. R.
    • Cordingley, N.
    • Flower, K. C.
    • Weeks, C.
  • Source: Field Crops Research
  • Volume: 132
  • Year: 2012
  • Summary: Cover crops have been successfully integrated into conservation agriculture systems in many parts of the world. They are primarily used to provide surface cover as well as to improve soil fertility and suppress weeds. Black oat (Avena strigosa Schreb.) is a widely used cereal cover crop with a rapid growth and high biomass production. It is being trialled as a cover crop for conservation agriculture systems in southwestern Australia, which has a Mediterranean climate with a short winter growing season and where terminal drought is common. Only one crop can be grown in a year and, as such, the long term benefits of including a cover crop in this system must outweigh the loss in income by not growing a cash crop. This study, which was part of a larger conservation agriculture cropping systems trial, examined the effect of different crop sequences, which included oat cover crops and grass pasture, on soil nitrogen mineralisation and weed control. A related paper in this Special Issue examined the effect of cover crops on the soil water balance. We hypothesised that the inclusion of high-biomass oat cover crops in a cereal-dominated cropping system would (i) result in less immobilisation of soil nitrogen compared with that of harvested cereals, and (ii) significantly improve the weed control. We show that soil N mineralisation following oat cover crops was similar to that following wheat and barley. Therefore, cash crops grown after oat cover crops would require similar levels of nitrogen to those grown after harvested cereals. Oat cover crops and grass pasture were found to be very effective in controlling weeds, even in continuous cereal rotations. Two consecutive years of cover crop were required for good annual ryegrass (Lolium rigidum Gaud.) control in a predominantly cereal rotation. Timing of when the cover crops were killed by herbicide was crucial for good weed control, as failure to prevent weed seed set resulted in significantly reduced weed control. Also, late killing of the cover crop reduced soil water storage. The inclusion of an oat cover crop in the rotation reduced the three-year average gross margin; however, the profitability of these crops needs to be evaluated over a longer period. To date, managed pasture, with herbicide control of weed seed set, appears to be a better option than oat cover crops because of the relatively low cost and increased soil water storage. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Taalimoghaddam, A.
    • Karbasi, A.
  • Source: Annals of Biological Research
  • Volume: 3
  • Issue: 7
  • Year: 2012
  • Summary: In this study, two goals are pursued. The first, will be addressed the relationship between game theory and linear programming and then, the application of game theory is checked for crops Khorasan Razavi province. Actually, this is a theory that is related to decide when two or more than two competitors compete in a rational. In this study, game theory model is used for the province's major crops include irrigated wheat, rain fed wheat, irrigated barley, rain fed barley, irrigated sugar beet and irrigated cotton. The data included time series of gross product values of the investigated crops for the period 2000-2009. In this study, in game theory have been used the "Wald" decision-making criterion to determine the highest income under the worst conditions. The pattern results Show irrigated sugar beet cultivation is risky product for the period studied. Irrigated sugar beet is included in the optimization program since it will be the highest expected income in the worst conditions. On the other hand, it has the highest coefficient of variation compared to the other crops. As a result, the game theory model is a good indicator for selecting alternative management strategies for farmers.