• Authors:
    • Nosrati,K.
    • Ahmadi,F.
  • Source: Journal of Applied Sciences and Environmental Management
  • Volume: 17
  • Issue: 2
  • Year: 2013
  • Summary: Soil organic carbon (SOC) and soil nitrogen (SN) are the principal components in soil quality assessment, and in mitigation the global greenhouse effect. In Iran, little information exists on the stocks of SOC and SN. SOC and SN stocks are a function of the SOC and SN concentrations and the bulk density of the soil that are prone to changes under land use types and soil erosion. The objective of this study was to evaluate SOC and SN stock in different land use types under surface erosion at catchment scale. In view of this, bulk density, SOC and SN concentration were measured in 39 different sampling sites of three main groups of land use affected by surface erosion namely, rangeland, crop field, and forest land at Taleghani catchment, Khoramabad, Iran. The results showed that SOC and SN stock under all land use types was significantly different (P rangeland (63.3 Mg ha -1) > crop field (47.2 Mg ha -1; P<0.01). Also the SN stock had the same trend in all studied land uses. These results can be useful as a scientific basis for selecting the proper soil management as a simple and low-cost approach to mitigate the SOC and SN loss.
  • Authors:
    • Xu, J.
    • Ostwald, M.
    • Moberg, J.
    • Persson, M.
  • Source: Journal of Environmental Management
  • Volume: 126
  • Year: 2013
  • Summary: The Grain for Green Programme (GGP) was launched in China in 1999 to control erosion and increase vegetation cover. Budgeted at USD 40 billion, GGP has converted over 20 million hectares of cropland and barren land into primarily tree-based plantations. Although GGP includes energy forests, only a negligible part (0.6%) is planted as such, most of the land (78%) being converted for protection. Future use of these plantations is unclear and an energy substitution hypothesis is valid. We estimate the overall carbon sequestration via GGP using official statistics and three approaches, based on i) net primary production, ii) IPCC's greenhouse gas inventory guidelines, and iii) mean annual increment. We highlight uncertainties associated with GGP and the estimates. Results indicate that crop- and barren-land conversion sequestered 222-468 Mt of carbon over GGP's first ten years, the IPCC approach yielding the highest estimate and the other two approaches yielding similar but lower estimates (approximately 250 Mt of carbon). The carbon stock in these plantation systems yields a mean of 12.3 t of carbon per hectare. Assessment uncertainties concern the use of growth curves not designed for particular species and locations, actual plantation survival rates, and discrepancies in GGP figures (e.g., area, type, and survival rate) at different authority levels (from national to local). The carbon sequestered in above- and below-ground biomass from GGP represents 14% (based on the median of the three approaches) of China's yearly (2009) carbon dioxide emissions from fossil fuel use and cement production.
  • Authors:
    • Ashraf, M.
    • Shahbaz, M.
    • Perveen, S.
  • Source: Photosynthetica
  • Volume: 51
  • Issue: 4
  • Year: 2013
  • Summary: A greenhouse experiment was conducted to examine the effect of foliar application of triacontanol (TRIA) on two cultivars (cv. S-24 and MH-97) of wheat ( Triticum aestivum L.) at different growth stages. Plants were grown in full strength Hoagland's nutrient solution under salt stress (150 mM NaCl) or control (0 mM NaCl) conditions. Three TRIA concentrations (0, 10, and 20 M) were sprayed over leaves at three different growth stages, i.e. vegetative (V), boot (B), and vegetative + boot (VB) stages (two sprays on same plants, i.e., the first at 30-d-old plants and the second 78-d-old plants). Salt stress decreased significantly growth, net photosynthetic rate ( PN), transpiration rate ( E), chlorophyll contents (Chl a and b), and electron transport rate (ETR), while membrane permeability increased in both wheat cultivars. Stomatal conductance ( gs ) decreased only in salt-sensitive cv. MH-97 under saline conditions. Foliar application of TRIA at different growth stages enhanced significantly the growth, PN, gs , Chl a and b contents, and ETR, while membrane permeability was reduced in both cultivars under salt stress. Of various growth stages, foliar-applied TRIA was comparatively more effective when it was applied at V and VB stages. Overall, 10 M TRIA concentration was the most efficient in reducing negative effects of salinity stress in both wheat cultivars. The cv. S-24 showed the better growth and ETR, while cv. MH-97 exhibited higher nonphotochemical quenching.
  • Authors:
    • Robertson, F.
    • Nash, D.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 165
  • Year: 2013
  • Summary: The extent to which soil C storage can be increased in Australian agricultural soils by adoption of improved management practices is poorly understood. There is a pressing need for such information in order to evaluate the potential for soil C sequestration to offset greenhouse gas emissions. In this study we used the RothC model to assess whether soil C accumulation under cropping using stubble retention and pasture rotations could be a significant offset for greenhouse gas emissions. We chose eight regions to represent the climatic range of the Victorian cropping industry: Walpeup, Birchip, Horsham, Bendigo, Rutherglen, Lismore, Bairnsdale and Hamilton (annual rainfall 330-700 mm). For each region, we chose two representative soil types, varying in clay and total organic C contents. For each region x soil combination, we compared the effects of five rotations: Canola-wheat-pulse-barley (C-W-P-B); Canola-wheat-triticale (C-W-T); Canola-wheat-barley-5 year perennial pasture (C-W-B-Pt5); Canola-wheat-fallow (C-W-F) and Continuous pasture (Pt). We compared the cropping rotations with cereal stubble burnt and with cereal stubble retained and, for two regions, with cereal stubble grazed by sheep. The results of the simulations showed that, across all scenarios, the equilibrium C density varied between 19 and 135 t C/ha to 300 mm depth, with potential soil C change being strongly influenced by crop yield, crop rotation, climate, initial soil C content, stubble management and continuity of management The simulations suggested that soil C stocks could be increased under a crop-pasture rotation (C-W-B-Pt5) with stubble retention, with rates of increase of 0.3-0.9 t C/ha yr over 25 years. If all of Victoria's cropland were converted to C-W-B-Pt5 rotation with stubble retention, and if 50% of the modelled potential C change were achieved, this would represent 3.0-4.5 MtCO(2)-e/year, equivalent to 2.5-3.7% of Victoria's greenhouse emissions. Less C accumulation would be possible under continuous cropping with stubble retention; even using the most conservative rotation (C-W-T) rates of C change varied from loss of 0.3 t C/ha yr to accumulation of 0.5 t C/ha yr over 25 years. If all of Victoria's cropland were converted to C-W-T rotation with stubble retention, and if 50% of the modelled potential C change were achieved, this would be equivalent to 0.8-2.3 MtCO(2)-e/year, or 0.7-1.9% of Victoria's greenhouse emissions. It would generally take 10-25 years for the soil C changes to become measurable using conventional soil sampling and analytical methods. Thus we conclude that, with current technology, the potential for significant and verifiable soil C accumulation in Victoria's croplands is limited.
  • Authors:
    • Macias, F.
    • Martin, F.
    • Verde, R.
    • Martinez, F.
    • Sierra, M.
  • Source: Soil & Tillage Research
  • Volume: 130
  • Year: 2013
  • Summary: The potential of soils as a sink of atmospheric carbon and the implications related to mitigate greenhouse-gas emissions are well recognized. The raising of tree crops on agricultural soils can augment soil-carbon sequestration more than do other agricultural uses such as corn crops. Thus, 6 plots with different durations of use as poplar plantation (5, 10, 20, 30, 50, and 100 years) were studied in comparison with 6 adjacent plots with corn crop. The carbon pool in poplar-plantation soils was positively correlated to the time of use at the three soil depths studied (0-20, 20-50, and 50-100 cm), the mean annual increase being 1.16 Mg C ha(-1) year(-1). Poplar-plantation soils also increased the total carbon content in a more effective way because the duration of use was also correlated with the most recalcitrant carbon forms. Therefore, land-use change from corn crops to poplar-plantation soils is economically profitable as well as positive both for the total organic-carbon pool as well as for the efficiency of carbon sequestration by the increase of non-oxidizable forms in the soil. (c) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Cotrufo, M. F.
    • Botte, J.
    • Zheng, J.
    • Stewart, C. E.
  • Source: GCB Bioenergy
  • Volume: 5
  • Issue: 2
  • Year: 2013
  • Summary: Char is a product of thermochemical conversion of biomass via pyrolysis, together with gas (syngas), liquid (bio-oil), and heat. Fast pyrolysis is a promising process for bio-oil generation, which leaves 1030% of the original biomass as char. Char produced for soil application, is defined biochar (BC), and it may increase soil C storage, and reduce soil emissions of greenhouse gases (GHG), such as N2O and CH4 potentially making fast pyrolysis bioenergy generation a C-negative system. However, differences in production conditions (e.g., feedstock, pyrolysis temperature and speed, post handling, and storage conditions) influence the chemical properties of BC and its net effect when added to soils. Understanding if fast pyrolysis BC can increase C sequestration and reduce GHG emissions will enable full assessment of the economic value and environmental benefits of this form of bioenergy. We characterized a BC produced by fast pyrolysis for bio-oil generation and examined GHG (CO2, N2O and CH4) efflux, C partitioning using 13C, and soil C sequestration across four temperate soils and five BC rates; 0%, 1%, 5%, 10%, and 20% w/w. The fast pyrolysis process created a highly aromatic, low N, ash-rich BC with a O:C ratio of 0.01, which we expected to be highly recalcitrant. Across soils, CO2 emissions increased linearly and N2O emissions decreased exponentially with increasing BC addition rates. Despite still being actively respired after 2years, total BC-derived C-CO2 comprised less than the BC volatile C content (4%). Expressed as CO2 equivalents, CO2 was the primary GHG emitted (97.5%), followed by N2O. All GHG emissions were small compared to the total SOC sequestered in the BC. Fast pyrolysis produced a highly recalcitrant BC that sequestered C and reduced GHG emissions. The recovery and soil application of BC would contribute to a negative carbon balance for this form of bioenergy generation.
  • Authors:
    • Nan, Z.
    • Tang, Z.
  • Source: Mitigation and Adaptation Strategies for Global Change
  • Volume: 18
  • Issue: 7
  • Year: 2013
  • Summary: It is generally accepted that cropland soils could be managed to store significant carbon (C), however little information is available regarding the cropland soil C sequestration potential of the Loess Plateau in northern China. This study aimed to estimate the cropland soil C sequestration potential in this area using the United Nations Intergovernmental Panel on Climate Change (IPCC) method with region-specific C stock change factors. The results show that the C sequestration potential can reach 6.054 Tg C yr(-1) (1Tg = 10(12) g) in cropland soils of the Loess Plateau using techniques that are currently available (no-tillage and high residue incorporation). Although the results show a high degree of uncertainty in this estimate with 95 % confidence interval ranges from 2.623 to 11.94 Tg C yr(-1), our study suggests that cropland soil C sequestration could play a meaningful role in helping to mitigate greenhouse gas increases in the Chinese Loess Plateau.
  • Authors:
    • Liao, Y.
    • Zhang, J.
    • Lu, X. L.
    • Wen, X.
    • Tanveer, S. K.
  • Source: PLOS ONE
  • Volume: 8
  • Issue: 9
  • Year: 2013
  • Summary: A two year (2010-2012) study was conducted to assess the effects of different agronomic management practices on the emissions of CO2 from a field of non-irrigated wheat planted on China's Loess Plateau. Management practices included four tillage methods i.e. T-1: (chisel plow tillage), T-2: (zero-tillage), T-3: (rotary tillage) and T-4: (mold board plow tillage), 2 mulch levels i.e., M-0 (no corn residue mulch) and M-1 (application of corn residue mulch) and 5 levels of N fertilizer (0, 80, 160, 240, 320 kg N/ha). A factorial experiment having a strip split-split arrangement, with tillage methods in the main plots, mulch levels in the sub plots and N-fertilizer levels in the sub-sub plots with three replicates, was used for this study. The CO2 data were recorded three times per week using a portable GXH-3010E1 gas analyzer. The highest CO2 emissions were recorded following rotary tillage, compared to the lowest emissions from the zero tillage planting method. The lowest emissions were recorded at the 160 kg N/ha, fertilizer level. Higher CO2 emissions were recorded during the cropping year 2010-11 relative to the year 2011-12. During cropping year 2010-11, applications of corn residue mulch significantly increased CO2 emissions in comparison to the non-mulched treatments, and during the year 2011-12, equal emissions were recorded for both types of mulch treatments. Higher CO2 emissions were recorded immediately after the tillage operations. Different environmental factors, i.e., rain, air temperatures, soil temperatures and soil moistures, had significant effects on the CO2 emissions. We conclude that conservation tillage practices, i.e., zero tillage, the use of corn residue mulch and optimum N fertilizer use, can reduce CO2 emissions, give better yields and provide environmentally friendly options.
  • Authors:
    • Thomas,Amy R. C.
    • Bond,Alan J.
    • Hiscock,Kevin M.
  • Source: Global Change Biology Bioenergy
  • Volume: 5
  • Issue: 3
  • Year: 2013
  • Summary: Reduction in energy sector greenhouse gas GHG emissions is a key aim of European Commission plans to expand cultivation of bioenergy crops. Since agriculture makes up 1012% of anthropogenic GHG emissions, impacts of land-use change must be considered, which requires detailed understanding of specific changes to agroecosystems. The greenhouse gas (GHG) balance of perennials may differ significantly from the previous ecosystem. Net change in GHG emissions with land-use change for bioenergy may exceed avoided fossil fuel emissions, meaning that actual GHG mitigation benefits are variable. Carbon (C) and nitrogen (N) cycling are complex interlinked systems, and a change in land management may affect both differently at different sites, depending on other variables. Change in evapotranspiration with land-use change may also have significant environmental or water resource impacts at some locations. This article derives a multi-criteria based decision analysis approach to objectively identify the most appropriate assessment method of the environmental impacts of land-use change for perennial energy crops. Based on a literature review and conceptual model in support of this approach, the potential impacts of land-use change for perennial energy crops on GHG emissions and evapotranspiration were identified, as well as likely controlling variables. These findings were used to structure the decision problem and to outline model requirements. A process-based model representing the complete agroecosystem was identified as the best predictive tool, where adequate data are available. Nineteen models were assessed according to suitability criteria, to identify current model capability, based on the conceptual model, and explicit representation of processes at appropriate resolution. FASSET, ECOSSE, ANIMO, DNDC, DayCent, Expert-N, Ecosys, WNMM and CERES-NOE were identified as appropriate models, with factors such as crop, location and data availability dictating the final decision for a given project. A database to inform such decisions is included.
  • Authors:
    • Venkateswarlu, B.
    • Rao,V. U. M.
  • Source: Climate Change Modeling, Mitigation, and Adaptation
  • Year: 2013