• Authors:
    • Wu, J.
    • Luo, Z. Z.
    • Wang, J.
    • Cai, L. Q.
    • Zhang, R. Z.
  • Source: Zhongguo Shengtai Nongye Xuebao / Chinese Journal of Eco-Agriculture
  • Volume: 21
  • Issue: 8
  • Year: 2013
  • Summary: This study analyzed the effects of different tillage conditions on greenhouse gas emissions of double sequence pea-wheat rotation fields during 2011. Three greenhouse gases (CO 2, N 2O and CH 4) emission were investigated under four tillage types [conventional tillage without straw mulching (T), no-tillage without straw mulching (NT), conventional tillage with straw mulching (TS) and no-tillage with straw mulching (NTS)]. The carbon dioxide analyzer and static chamber-gas chromatographic techniques were used to continuously measure and analyze the greenhouse gases fluxes. The results showed that double sequence pea-wheat rotation fields served not only as source of atmospheric CO 2, N 2O, but also as sink of atmospheric CH 4. Compared with T, NT retarded CO 2 emission. The three conservation tillage methods of NTS, NT and TS reduced N 2O emission but significantly increased CH 4 absorption. CO 2 and N 2O fluxes were significantly correlated with topsoil temperature ( R2=0.92** and 0.89**), soil temperature at the 5 cm soil depth ( R2=0.95** and 0.91**) and soil temperature at the 10 cm soil depth ( R2=0.77* and 0.62*). CH 4 fluxes were uncorrected with soil temperature at different soil depths. The correlation coefficients between CO 2 and soil water content, and CH 4 and soil water content at 0-5 cm soil layer were 0.69* and 0.72*, respectively. The correlation coefficient between CO 2 and soil water content at the 5-10 cm soil layer was 0.77* and that between CH 4, and soil water content at the 5-10 cm soil layer was 0.64*. CO 2, CH 4, fluxes were positively correlated with soil water content at the 10-30 cm soil layer. N 2O fluxes showed negative correlations with soil water content at different soil layers. The calculated global warming potential of the three greenhouse gases under the different tillage conditions showed that NT limited greenhouse gas flux, thereby reducing greenhouse effect.
  • Authors:
    • Cowie, B. A.
    • Thornton, C. M.
    • Dalal, R. C.
  • Source: SCIENCE OF THE TOTAL ENVIRONMENT Special Issue: SI
  • Volume: 465
  • Year: 2013
  • Summary: The continuing clearance of native vegetation for pasture, and especially cropping, is a concern due to declines in soil organic C (SOC) and N, deteriorating soil health, and adverse environment impact such as increased emissions of major greenhouse gases (CO2, N2O and CH4). There is a need to quantify the rates of SOC and N budget changes, and the impact on greenhouse gas emissions from land use change in semi-arid subtropical regions where such data are scarce, so as to assist in developing appropriate management practices. We quantified the turnover rate of SOC from changes in delta C-13 following the conversion of C-3 native vegetation to C-4 perennial pasture and mixed C-3/C-4 cereal cropping (wheat/sorghum), as well as delta N-15 changes following the conversion of legume native vegetation to non-legume systems over 23 years. Perennial pasture (Cenchrus ciliaris cv. Biloela) maintained SOC but lost total N by more than 20% in the top 0-0.3 m depth of soil, resulting in reduced animal productivity from the grazed pasture. Annual cropping depleted both SOC and total soil N by 34% and 38%, respectively, and resulted in decreasing cereal crop yields. Most of these losses of SOC and total N occurred from the >250 mu m fraction of soil. Moreover, this fraction had almost a magnitude higher turnover rates than the 250-53 mu m and <53 mu m fractions. Loss of SOC during the cropping period contributed two-orders of magnitude more CO2-e to the atmosphere than the pasture system. Even then, the pasture system is not considered as a benchmark of agricultural sustainability because of its decreasing productivity in this semi-arid subtropical environment. Introduction of legumes (for N-2 fixation) into perennial pastures may arrest the productivity decline of this system. Restoration of SOC in the cropped system will require land use change to perennial ecosystems such as legume-grass pastures or native vegetation. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Ahmad, W.
    • Biswas, W. K.
    • Engelbrecht, D.
  • Source: Journal of Cleaner Production
  • Volume: 57
  • Year: 2013
  • Summary: The International Panel on Climate Change (IPCC) predicts an increase of 0.2 degrees C per decade for the next two decades in global temperatures and a rise of between 1.5 and 4.5 degrees C by the year 2100. Related to the increase in world temperatures is the increase in Greenhouse Gases (GHGs) which are primarily made up of carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4) and fluorinated gases. In 2004, the GHGs from agriculture contributed 14% of the overall global GHGs made up mainly of methane (CH4) and nitrous oxide (N2O) emissions. In Australia, the dominant source of CH4 and N2O emissions for the year ending June 2012 was found to be from the agricultural sector. With the recent introduction of the Clean Energy Act 2011, the agricultural sector of Australia is expected to develop appropriate GHG mitigation strategies to maintain and improve its competitiveness in the green commodity market. This paper proposes the use of Integrated Spatial Technologies (IST) framework by linking Life Cycle Assessment (LCA), Remote Sensing (RS) and Geographical Information Systems (GIS). The IST approach also integrates and highlights the use of Cleaner Production (CP) strategies for the formulation and application of cost-effective GHG mitigation options for grain production in Western Australia (WA). In this study, the IST framework was tested using data from an existing study (the baseline study) and two mitigation options. The analysis results revealed production and use of fertiliser as the "hotspot", and for mitigation purposes was replaced with pig manure in option I, whereas option 2 emphasised crop rotation system/s.
  • Authors:
    • Partington, D. L.
    • Phelan, A. J.
    • Zollinger, R. P.
    • Fogarty, K. M.
    • Armstrong, R. D.
    • Hill, P. A.
    • Officer, S. J.
    • Harris, R. H.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 95
  • Issue: 2
  • Year: 2013
  • Summary: Nitrous oxide (N2O) is a potent greenhouse gas released from high rainfall cropping soils, but the role of management in its abatement remains unclear in these environments. To quantify the relative influence of management, nitrogen (N) fertiliser and soil nitrification inhibitor was applied to separate but paired raised bed and conventionally flat field experiments in south west Victoria, to measure emissions and income from wheat and canola planted 2 and 3 years after conversion from a long-term pasture. Management included four different rates of N fertiliser, top-dressed with and without the nitrification inhibitor Dicyandiamide (DCD), which was applied in solution to the soil in the second year of experimentation. Crop biomass, grain yield, soil mineral N, soil temperature and soil water and N2O flux were measured. Static chamber methodology was used to identify relative differences in N2O loss between management. In the second crop (wheat) following conversion, N2O losses were up to 72 % lower (P < 0.05) in the furrows, receiving the lower rate of N fertiliser compared with the highest rate, with less frequent reductions observed in the third crop (canola); losses of N2O from the beds was unaffected by N rate, perhaps from nitrate leakage into the adjacent furrow of the raised bed experiment. On the nearby flat experiment, nitrate leaching may have diminished the effects of N rate and DCD on N2O flux. Furthermore the extra N did not significantly increase grain yield in either the wheat or canola crops on both experiments. The application of DCD in the canola crop temporarily reduced (P < 0.05) N2O production by up to 84 % from the beds, 83 % in the adjacent furrows and 75 % on the flat experiment. Grain yield was not significantly (P < 0.001) affected however, canola income was reduced by $1407/ha and $1252/ha, compared with no addition of inhibitor on the respective bed and flat experiments. Although N2O fluxes are driven by environmental episodic events, management will play a role in N2O abatement. However, DCD currently appears economically unfeasible and matching N fertiliser supply to meet crop demand appears a better option for minimising N2O losses from high rainfall cropping systems.
  • Authors:
    • Sanderman, J.
    • Chappell, A.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 1
  • Year: 2013
  • Summary: The movement of soil organic carbon (SOC) during erosion and deposition events represents a major perturbation to the terrestrial carbon cycle. Despite the recognized impact soil redistribution can have on the carbon cycle, few major carbon accounting models currently allow for soil mass flux. Here, we modified a commonly used SOC model to include a soil redistribution term and then applied it to scenarios which explore the implications of unrecognized erosion and deposition for SOC accounting. We show that models that assume a static landscape may be calibrated incorrectly as erosion of SOC is hidden within the decay constants. This implicit inclusion of erosion then limits the predictive capacity of these models when applied to sites with different soil redistribution histories. Decay constants were found to be 15-50% slower when an erosion rate of 15 t soil ha -1 yr -1 was explicitly included in the SOC model calibration. Static models cannot account for SOC change resulting from agricultural management practices focused on reducing erosion rates. Without accounting for soil redistribution, a soil sampling scheme which uses a fixed depth to support model development can create large errors in actual and relative changes in SOC stocks. When modest levels of erosion were ignored, the combined uncertainty in carbon sequestration rates was 0.3-1.0 t CO 2 ha -1 yr -1. This range is similar to expected sequestration rates for many management options aimed at increasing SOC levels. It is evident from these analyses that explicit recognition of soil redistribution is critical to the success of a carbon monitoring or trading scheme which seeks to credit agricultural activities.
  • Authors:
    • Payero, J.
    • Rowlings, D. W.
    • Grace, P. R.
    • Scheer, C.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 95
  • Issue: 1
  • Year: 2013
  • Summary: Irrigation is known to stimulate soil microbial carbon and nitrogen turnover and potentially the emissions of nitrous oxide (N2O) and carbon dioxide (CO2). We conducted a study to evaluate the effect of three different irrigation intensities on soil N2O and CO2 fluxes and to determine if irrigation management can be used to mitigate N2O emissions from irrigated cotton on black vertisols in South-Eastern Queensland, Australia. Fluxes were measured over the entire 2009/2010 cotton growing season with a fully automated chamber system that measured emissions on a sub-daily basis. Irrigation intensity had a significant effect on CO2 emission. More frequent irrigation stimulated soil respiration and seasonal CO2 fluxes ranged from 2.7 to 4.1 Mg-C ha(-1) for the treatments with the lowest and highest irrigation frequency, respectively. N2O emission happened episodic with highest emissions when heavy rainfall or irrigation coincided with elevated soil mineral N levels and seasonal emissions ranged from 0.80 to 1.07 kg N2O-N ha(-1) for the different treatments. Emission factors (EF = proportion of N fertilizer emitted as N2O) over the cotton cropping season, uncorrected for background emissions, ranged from 0.40 to 0.53 % of total N applied for the different treatments. There was no significant effect of the different irrigation treatments on soil N2O fluxes because highest emission happened in all treatments following heavy rainfall caused by a series of summer thunderstorms which overrode the effect of the irrigation treatment. However, higher irrigation intensity increased the cotton yield and therefore reduced the N2O intensity (N2O emission per lint yield) of this cropping system. Our data suggest that there is only limited scope to reduce absolute N2O emissions by different irrigation intensities in irrigated cotton systems with summer dominated rainfall. However, the significant impact of the irrigation treatments on the N2O intensity clearly shows that irrigation can easily be used to optimize the N2O intensity of such a system.
  • Authors:
    • Lehmann, J.
    • Lal, R.
    • Jastrow, J. D.
    • Chenu, C.
    • Brookes, P. C.
    • Bird, M.
    • Baldock, J.
    • Angers, D. A.
    • Abbott, L.
    • Wheeler, I.
    • Singh, K.
    • Courcelles, V. de R. de
    • McBratney, A. B.
    • Minasny, B.
    • Jenkins, M.
    • Henakaarchchi, N.
    • Field, D. J.
    • Crawford, J. W.
    • Adams, M. A.
    • Stockmann, U.
    • O'Donnell, A. G.
    • Parton, W. J.
    • Whitehead, D.
    • Zimmermann, M.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 164
  • Year: 2013
  • Summary: Soil contains approximately 2344 Gt (1 gigaton=1 billion tonnes) of organic carbon globally and is the largest terrestrial pool of organic carbon. Small changes in the soil organic carbon stock could result in significant impacts on the atmospheric carbon concentration. The fluxes of soil organic carbon vary in response to a host of potential environmental and anthropogenic driving factors. Scientists worldwide are contemplating questions such as: 'What is the average net change in soil organic carbon due to environmental conditions or management practices?', 'How can soil organic carbon sequestration be enhanced to achieve some mitigation of atmospheric carbon dioxide?' and 'Will this secure soil quality?'. These questions are far reaching, because maintaining and improving the world's soil resource is imperative to providing sufficient food and fibre to a growing population. Additional challenges are expected through climate change and its potential to increase food shortages. This review highlights knowledge of the amount of carbon stored in soils globally, and the potential for carbon sequestration in soil. It also discusses successful methods and models used to determine and estimate carbon pools and fluxes. This knowledge and technology underpins decisions to protect the soil resource.
  • Authors:
    • Hulugalle, N. R.
  • Source: Crop and Pasture Science
  • Volume: 64
  • Issue: 8
  • Year: 2013
  • Summary: Partial mitigation of global warming caused by accelerated emissions of greenhouse gases such as carbon dioxide may be possible by storing atmospheric carbon in soils. Carbon storage is influenced by processes and properties that affect soil aggregation, such as clay and silt concentrations and mineralogy, intensity and frequency of wet/dry cycles, and microbial activity. Microbial activity, in turn, is influenced by factors such as temperature, nutrient and water availability, and residue quality. The objective of this study was to assess the influence of average annual maximum temperature on soil carbon storage in Vertosols under cotton-based farming systems. This paper reports a re-evaluation of results obtained from a series of experiments on cotton-farming systems conducted in eastern Australia between 1993 and 2010. The experimental sites were in the Macquarie and Namoi Valleys of New South Wales, and the Darling Downs and Central Highlands of Queensland. Average soil organic carbon storage in the 0-0.6m depth was highest in a Black Vertosol in Central Queensland and lowest in a Grey Vertosol that was irrigated with treated sewage effluent at Narrabri. At other sites, average values were generally comparable and ranged from 65 to 85 t C/ha. Climatic parameters such as ambient maximum temperature, T-max, and rainfall at rainfed sites (but not irrigated sites) were also related to soil organic carbon storage. At most sites, variations in carbon storage with average ambient maximum temperature were described by Gaussian models or bell-shaped curves, which are characteristic of microbial decomposition. Carbon storage occurred at peak rates only for a very limited temperature range at any one site, with these temperatures increasing with decreasing distance from the equator. The exception was a site near Narrabri that was irrigated with treated sewage effluent, where the relationship between soil organic carbon and T-max was linear. The decrease or absence of change in soil carbon storage with time reported in many Australian studies of annual cropping systems may be due to carbon storage occurring within a limited temperature range, whereas intra-seasonal average maximum temperatures can range widely. Further research needs to be conducted under field conditions to confirm these observations.
  • Authors:
    • Finlay, L. A.
    • Weaver, T. B.
    • Hulugalle, N. R.
    • Heimoana, V.
  • Source: CROP & PASTURE SCIENCE
  • Volume: 64
  • Issue: 8
  • Year: 2013
  • Summary: Long-term studies of soil organic carbon dynamics in two- and three-crop rotations in irrigated cotton (Gossypium hirsutum L.) based cropping systems under varying stubble management practices in Australian Vertosols are relatively few. Our objective was to quantify soil organic carbon dynamics during a 9-year period in four irrigated, cotton-based cropping systems sown on permanent beds in a Vertosol with restricted subsoil drainage near Narrabri in north-western New South Wales, Australia. The experimental treatments were: cotton-cotton (CC); cotton-vetch (Vicia villosa Roth. in 2002-06, Vicia benghalensis L. in 2007-11) (CV); cotton-wheat (Triticum aestivum L.), where wheat stubble was incorporated (CW); and cotton-wheat-vetch, where wheat stubble was retained as in-situ mulch (CWV). Vetch was terminated during or just before flowering by a combination of mowing and contact herbicides, and the residues were retained as in situ mulch. Estimates of carbon sequestered by above- and below-ground biomass inputs were in the order CWV>>CW=CV>CC. Carbon concentrations in the 0-1.2m depth and carbon storage in the 0-0.3 and 0-1.2m depths were similar among all cropping systems. Net carbon sequestration rates did not differ among cropping systems and did not change significantly with time in the 0-0.3m depth, but net losses occurred in the 0-1.2m depth. The discrepancy between measured and estimated values of sequestered carbon suggests that either the value of 5% used to estimate carbon sequestration from biomass inputs was an overestimate for this site, or post-sequestration losses may have been high. The latter has not been investigated in Australian Vertosols. Future research efforts should identify the cause and quantify the magnitude of these losses of organic carbon from soil.
  • 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.