• Authors:
    • Omonode, R.
    • Vyn, T.
  • Source: Agronomy Journal
  • Volume: 105
  • Issue: 6
  • Year: 2013
  • Summary: Simultaneous application of nitrification inhibitors and fertilizer N has the potential to delay nitrification processes and reduce atmospheric N loss through N2O emissions. A 2-yr study was conducted to assess the effects of newly available water-soluble nitrapyrin (Instinct) [2-chloro-6-(trichloromethyl) pyridine] on the nitrification kinetics and N2O emissions from urea-NH4NO3 (UAN) band applied to somewhat poorly drained and moderately well-drained silt loam soils in Indiana. The UAN fertilizer, with or without nitrapyrin, was injected post-emergence between corn (Zea mays L.) rows that were 76 cm apart. Soil samples were taken at various increments from the band centers at 1- to 2-wk intervals for up to 14 wk and analyzed for NH4- and NO3-N concentrations. Nitrification rates were determined using appropriate kinetic models. Greenhouse gas samples were collected weekly for 7 to 10 wk and biweekly thereafter for an additional 2 to 4 wk. Our results showed that UAN nitrification followed first-order kinetics, with significantly greater nitrification rate constants without nitrapyrin. On average, UAN half-life was about 15 d without nitrapyrin and 25 d when coapplied with nitrapyrin. Nitrapyrin reduced N2O emissions by up to 44% from sidedress-applied UAN, even though emission quantities varied by location and year due to differences in soil moisture, temperature, and precipitation. These latter variables plus soil NH4-N concentrations, in various combinations, accounted for 40 to 50% of the total variability associated with N2O emissions. These results can help inform UAN management decisions with regard to use of N stabilizers with UAN in the midwestern United States.
  • Authors:
    • Ouyang, W.
    • Qi, S.
    • Hao, F.
    • Wang, X.
    • Shan, Y.
    • Chen, S.
  • Source: Ecological Modelling
  • Volume: 252
  • Year: 2013
  • Summary: Agricultural activity is a primary factor contributing to global warming. In higher latitude freeze zone, agricultural activities pose a more serious threat to global warming than other zones. The crop management practices of various land use types have direct impacts on soil organic carbon (SOC) and global warming potential (GWP). Crop variations and cultivation practices are two important factors affecting carbon sequestration and the exchange of greenhouse gases between soils and the atmosphere. This exchange has special characteristics in the freeze zone. In this paper, the impact of crop patterns and cultivation management (i.e., residue return rate, manure amendment, and chemical N fertiliser application) on SOC and GWP in an agricultural freeze zone was analysed. The Denitrification-Decomposition (DNDC) model was employed to predict the long-term dynamics of nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) for diyland and paddy rice systems. The CO2-equivalent index was used to express the GWP response of N2O, CH4 and CO2. The simulated results indicated that the manure amendment and N fertiliser application can improve the SOC, increase crop production and enhance the GWP. The cultivation of returning residue to the soil is the win-win solution for SOC conservation and GWP control. It was found that paddy rice was preferable to dryland for sequestering atmospheric CO2 and mitigating global warming. This analysis also indicated that the DNDC model is a valid tool for predicting the consequences of SOC and GWP changes in cropland agroecosystems in the freeze zone. (C) 2012 Elsevier B.V. All rights reserved.
  • 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:
    • Rimal, B.
    • Lal, R.
    • Shrestha, R.
  • Source: Geoderma
  • Volume: 197
  • Year: 2013
  • Summary: The addition of organic amendments is essential for sustainable soil fertility management and crop production, but can also increase greenhouse gas (GHG) emissions. Thus, understanding the impacts of organic soil amendments on gaseous emissions is pertinent to minimizing agricultural impacts on the net emissions of GHGs. A long-term field experiment was conducted to assess the impacts of continuous application of organic amendments (i.e. compost and farmyard manure) and cover crop [mixture of rye (Secale cereal), red fescue (Festuca rubra), and blue grass (Poa pratensis L)] on selected soil properties, apparent carbon (C) budget (calculated from the difference of sum of all sources of C inputs and outputs), gaseous flux (i.e. carbon dioxide, CO2, and methane, CH4), and relationship with weather parameters under no-till (NT) corn (Zea mays L) cultivation in an Alfisol of central Ohio, USA. Soil properties and gaseous fluxes were measured continuously for 2 years. Ten years of continuous application of soil amendments increased soil pH and electrical conductivity, enhanced soil C pool, and decreased bulk density especially in 0-5 cm depth than that with cover crop and control plots. Two years average, cattle manure, compost, fallow, and cover crop emitted 14.1, 10.2, 7.5, and 7.2 Mg CO2-C ha(-1) yr(-1), respectively. Methane emission was 10.7 kg CH4-C ha(-1) yr(-1) from cattle manure and 4.0 kg CH4-C ha(-1) yr(-1) from compost However, fallow consumed 3.3 and cover crop 5.0 kg CH4-C ha(-1) yr(-1). These data suggest that long-term application of compost in NT corn decreased emissions of CO2 by 38% and of CH4 by 167% compared to application of manuring. In general, soil temperature, air temperature, and precipitation were positively correlated with CO2 emissions. Estimation of C budget indicated that amended soil under NT is a C-sink while a non-amended system is a C-source. The application of composted soil amendments in NT corn enhances soil quality and reduces net GHG emissions. Published by Elsevier B.V.
  • Authors:
    • Conant, R.
    • Cerri, C.
    • Signor, D.
  • Source: Environmental Research Letters
  • Volume: 8
  • Issue: 1
  • Year: 2013
  • Summary: Among the main greenhouse gases (CO2, CH4 and N2O), N2O has the highest global warming potential. N2O emission is mainly connected to agricultural activities, increasing as nitrogen concentrations increase in the soil with nitrogen fertilizer application. We evaluated N2O emissions due to application of increasing doses of ammonium nitrate and urea in two sugarcane fields in the mid-southern region of Brazil: Piracicaba (Sao Paulo state) and Goianesia (Goias state). In Piracicaba, N2O emissions exponentially increased with increasing N doses and were similar for urea and ammonium nitrate up to a dose of 107.9 kg ha(-1) of N. From there on, emissions exponentially increased for ammonium nitrate, whereas for urea they stabilized. In Goianesia, N2O emissions were lower, although the behavior was similar to that at the Piracicaba site. Ammonium nitrate emissions increased linearly with N dose and urea emissions were adjusted to a quadratic equation with a maximum amount of 113.9 kg N ha(-1). This first effort to measure fertilizer induced emissions in Brazilian sugarcane production not only helps to elucidate the behavior of N2O emissions promoted by different N sources frequently used in Brazilian sugarcane fields but also can be useful for future Brazilian ethanol carbon footprint studies.
  • 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:
    • Zhang, Z.
    • Tao, F.
  • Source: Agricultural and Forest Meteorology
  • Volume: 170
  • Year: 2013
  • Summary: Ensemble-based probabilistic projection is an effective approach to deal with the uncertainties in climate change impact assessments and to inform adaptations. Here, the crop model MCWLA-Wheat was firstly developed by adapting the process-based general crop model, MCWLA [Tao, F., Yokozawa, M., Zhang, Z., 2009a. Modelling the impacts of weather and climate variability on crop productivity over a large area: a new process-based model development, optimization, and uncertainties analysis. Agric. For. Meteorol. 149, 831-850], to winter wheat. Then the Bayesian probability inversion and a Markov chain Monte Carlo (MCMC) technique were applied to the MCWLA-Wheat to analyse uncertainties in parameters estimations, and to optimize parameters. Ensemble hindcasts showed that the MCWLA-Wheat could capture the interannual variability of detrended historical yield series fairly well, especially over a large area. Finally, based on the MCWLA-Wheat, a super-ensemble-based probabilistic projection system was developed and applied to project the probabilistic responses of wheat productivity and water use in the North China Plain (NCP) to future climate change. The system used 10 climate scenarios consisting of the combinations of five global climate models and two greenhouse gases emission scenarios (A1FI and B1), the corresponding atmospheric CO2 concentration range, and multiple sets of crop model parameters representing the biophysical uncertainties from crop models. The results showed that winter wheat yields in the NCP could increase with high probability in future due to climate change. During 2020s, 2050s, and 2080s, with (without) CO2 fertilization effects, relative to 1961-1990 level, simulated wheat yields would increase averagely by up to 37.7% (18.6%), 67.8% (23.1%), and 87.2% (34.4%), respectively, across 80% of the study area; simulated changes in evaportranspiration during wheat growing period would range generally from -6% to 6% (-0.6% to 10%), from -10% to 8% (-1.0% to 17%), and from -17% to 4% (7-12%), respectively, across the study area. Further analyses suggested that the improvements in heat and water resources and rising atmospheric CO2 concentration ([CO2]) could contribute notably to wheat productivity increase in future. Climate change could enhance the development and photosynthesis rate; however the duration of reproductive period could be less affected than that of vegetative period, and wheat productivity could benefit from enhanced photosynthesis due to climate change and rising [CO2]. Furthermore, wheat could become mature earlier, which could prevent it from severe high temperature stress. Our study parameterized explicitly the effects of high temperature stress on productivity, accounted for a wide range of crop cultivars with contrasting phenological and thermal characteristics, and presented new findings on the probabilistic responses of wheat productivity and water use to climate change in the NCP.
  • 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.