• Authors:
    • Rosas,Francisco
    • Babcock,Bruce A.
    • Hayes,Dermot J.
  • Source: Climatic Change
  • Volume: 132
  • Issue: 2
  • Year: 2015
  • Summary: Farmers may choose to apply nitrogen fertilizer at a rate that exceeds the average ex post agronomically optimal rate when the yield response to nitrogen varies across growing seasons. Negative environmental consequences such as nitrous oxide (N2O) emissions and/or water pollution can result when all the applied nitrogen is not needed by the crop. Here we consider a nonlinear market instrument targeting farmers' nitrogen use, and by solving for the optimal nitrogen reduction using a model of expected utility of farm profits, we evaluate the induced N2O emission reductions that are consistent with the instrument introduced. The market instrument is nonlinear because of the expected nonlinear relationship between N2O and nitrogen application rates. Our simulations show that, in cases where farmers apply N at rates which exceed recommendations and the N2O response is likely to be non-linear, payments will induce participation in the program and will have a significant impact on both expected and actual N2O emissions without significantly harming expected or actual yields. Failure to consider this nonlinearity would deviate the attention away from N2O pollution because it would require large N reductions (and crop yields) to achieve equivalent N2O abatement.
  • Authors:
    • Wang Zhan-biao
    • Wen Xin-ya
    • Zhang Hai-lin
    • Lu Xiao-hong
    • Chen Fu
  • Source: Journal of Integrative Agriculture
  • Volume: 14
  • Issue: 8
  • Year: 2015
  • Summary: Excessive use of N fertilizer in intensive agriculture can increase crop yield and at the same time cause high carbon (C) emissions. This study was conducted to determine optimized N fertilizer application for high grain yield and lower C emissions in summer corn (Zea mays L.). Afield experiment, including 0 (NO), 75(N75), 150 (N150), 225 (N225), and 300 (N300) kg N ha(-1) treatments, was carried out during 2010-2012 in the North China Plain (NCP). The results showed that grain yield, input energy, greenhouse gas (GHG) emissions, and carbon footprint (CF) were all increased with the increase of N rate, except net energy yield (NEY). The treatment of N225 had the highest grain yield (10364.7 kg ha(-1)) and NEY (6.8%), but the CF (0.25) was lower than that of N300, which indicates that a rate of 225 kg N ha(-1) can be optimal for summer corn in NCR Comparing GHG emision compontents, N fertilizer (0-51.1%) was the highest and followed by electricity for irrigation (19.73-49.35%). We conclude that optimazing N fertilizer application rate and reducing electricity for irrigation are the two key measures to increase crop yield, improve energy efficiency and decrease GHG emissions in corn production.
  • Authors:
    • Xu,X.
  • Source: Acta Scientiae Circumstantiae
  • Volume: 35
  • Issue: 8
  • Year: 2015
  • Summary: Farmland releases greenhouse gases, therefore is of great importance to climate change. Carbon footprint is an ideal method to evaluate comprehensive greenhouse gas emissions of crops through the entire life cycle. This study took Jinzhong City, Shanxi Province, a typical winter wheat planting area as an example. Carbon footprint of wheat production was calculated using life cycle assessment. Furthermore, carbon footprint was optimized based on nonlinear programming aiming at reducing carbon emission as well as increasing crop unit yield. Results showed that, after energy-based allocating, carbon footprint for 1000 kg wheat production was 1357.28 kg CO2 equivalent under traditional farm management. Two major phrases of carbon footprint generation were N2O emission from farmland and urea manufacture. Through altering the fertilizer amount and adjusting the ratio of urea and mature, carbon footprint of 1000 kg wheat production could be reduced to 469.99 kg CO2 equivalent, with 9.13% increase in unit yield. Carbon footprint of wheat production in Jinzhong City showed great difference with results from previous studies in China, which was most likely due to various fertilizer amounts and N2O emission coefficients in different studies. This study provides important information in integrated greenhouse gas emissions of wheat production and quantitative methods to decrease carbon emission and increase crop yield. ©, 2015, Science Press. All right reserved.
  • Authors:
    • Franklin,D.
    • Bender-Özenç,D.
    • Özenç,N.
    • Cabrera,M.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 5
  • Year: 2015
  • Summary: composts and soil conditioners may be useful soil amendments to provide organic matter as well as nutrients such as n and P, but net n mineralized and P released can vary greatly among materials. consequently, it is important to identify the material characteristics that control these processes. Furthermore, the magnitude of these processes may be affected by particle size. we conducted two laboratory studies at 30°c to: (i) identify variables that can be used to estimate n mineralized and Mehlich-1 P released from 14 composts and soil conditioners; and (ii) evaluate net n mineralized from three size fractions (<1.0 mm, 1.0-2.0, and 2.0-4.0 mm) of five different composts. organic n content and c/n ratio explained 83% of the variability in the amount of net n mineralized or immobilized per unit of material from the 14 composts or conditioners in 214 d. similarly, organic n content and total P content explained 99% of the variability in the amount of Mehlich-1 P released per unit of material. in the study with size fractions, we found that larger size fractions (1-4 mm) mineralized more n (4% of applied n) than the 0-to 1-mm size fraction (0.5%). these results indicate that sieving composts to obtain specific size fractions may affect the rate of n mineralization. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All Rights reserved.
  • Authors:
    • Guo,Miao
    • Li,Changsheng
    • Facciotto,Gianni
    • Bergante,Sara
    • Bhatia,Rakesh
    • Comolli,Roberto
    • Ferre,Chiara
    • Murphy,Richard
  • Source: Biotechnology for Biofuels
  • Volume: 8
  • Year: 2015
  • Summary: Background: Environmental issues, e.g. climate change, fossil resource depletion have triggered ambitious national/regional policies to develop biofuel and bioenergy roles within the overall energy portfolio to achieve decarbonising the global economy and increase energy security. With the 10 % binding target for the transport sector, the Renewable Energy Directive confirms the EU's commitment to renewable transport fuels especially advanced biofuels. Imola is an elite poplar clone crossed from Populus deltoides Bartr. and Populus nigra L. by Research Units for Intensive Wood Production, Agriculture Research Council in Italy. This study examines its suitability for plantation cultivation under short or very short rotation coppice regimes as a potential lignocellulosic feedstock for the production of ethanol as a transport biofuel. A life cycle assessment (LCA) approach was used to model the cradle-to-gate environmental profile of Imola-derived biofuel benchmarked against conventional fossil gasoline. Specific attention was given to analysing the agroecosystem fluxes of carbon and nitrogen occurring in the cultivation of the Imola biomass in the biofuel life cycle using a process-oriented biogeochemistry model (DeNitrification-DeComposition) specifically modified for application to 2G perennial bioenergy crops and carbon and nitrogen cycling. Results: Our results demonstrate that carbon and nitrogen cycling in perennial crop-soil ecosystems such as this example can be expected to have significant effects on the overall environmental profiles of 2G biofuels. In particular, soil carbon accumulation in perennial biomass plantations is likely to be a significant component in the overall greenhouse gas balance of future biofuel and other biorefinery products and warrants ongoing research and data collection for LCA models. We conclude that bioethanol produced from Imola represents a promising alternative transport fuel offering some savings ranging from 35 to 100 % over petrol in global warming potential, ozone depletion and photochemical oxidation impact categories. Conclusions: Via comparative analyses for Imola-derived bioethanol across potential supply chains, we highlight priority issues for potential improvement in 2G biofuel profiling. Advanced clones of poplar such as Imola for 2G biofuel production in Italy as modelled here show potential to deliver an environmentally sustainable lignocellulosic biorefinery industry and accelerate advanced biofuel penetration in the transport sector.
  • Authors:
    • Hua,Keke
    • Zhu,Bo
    • Wang,Xiaoguo
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 103
  • Issue: 1
  • Year: 2015
  • Summary: Soil carbon dioxide (CO2) and methane (CH4) emissions, as well as runoff and leaching are major pathways of soil organic carbon (SOC) loss, which affect SOC sequestration in croplands. However, fluxes and relationships of the four pathways are still poorly understood. Static chamber-GC techniques were used to measure soil heterotrophic respiration rate and CH4 emission flux on hillslope upland of Regosol soil in Southwest China under traditional mineral fertilizer treatment from 2010 to 2012. Synchronously, SOC loss flux via overland flow, leaching and sediment was measured using free-drained lysimeters (8 m x 4 m). Average annual cumulative soil CO2 emission and CH4 uptake fluxes were 462.8 +/- A 52.2 and -1.1 +/- A 0.16 g cm(-2). Average annual cumulative dissolved organic carbon (DOC) loss fluxes via overland flow and leaching were 0.16 +/- A 0.03 and 0.92 +/- A 0.08 g cm(-2), respectively and organic C loss via sediment was 2.2 +/- A 0.3 g cm(-2). Relationship between DOC loss fluxes and soil heterotrophic respiration rates under natural rainfall events could be described by a significant exponential decay function (R = -0.63, P < 0.01). Moreover, a significantly negative correlation was also found between DOC loss flux and soil DOC content in topsoil at 15 cm depth (R = -0.75, P < 0.05). In conclusion, DOC loss decreases soil DOC content and is an underrated negative regulating factor of soil CO2 emission, especially in the regions where high DOC losses occur.
  • Authors:
    • Panday,D.
    • Nkongolo,N. V.
  • Source: Procedia Environmental Sciences
  • Volume: 29
  • Year: 2015
  • Summary: Knowledge of the impact of soil and crop management practices on soil processes is important in the study of greenhouse gases emissions from agricultural fields. We assessed the effect of soil air (pore space indices) and water (content, theta; and potential, Psi) on greenhouse gases emissions in corn/soybean field. The study was conducted in 2011 and 2012 on a silt loam soil at Freeman farm of Lincoln University. Soil samples were collected at four depths: 0-10, 10-20, 20-40 and 40-60 cm and they were oven dried at 105°C for 72 h for the calculation of air filled porosity (AFP), total pore space (TPS) and other soil physical properties. Pore space indices were computed using diffusivity models based on AFP and TPS. Soil samples were later saturated then brought into a pressure plate for measurements of moisture content (theta) at five different water potentials (Psi). Soil air samples for the measurements of greenhouse gases emissions were collected using static and vented chambers of 30 cm height and 20 cm diameter. The concentrations of CO2, CH4 and N2O in soil air samples were determined using a Gas Chromatograph GC-14. Results showed that pore space indices significantly correlated with greenhouse gases fluxes (p<0.05) with correlation coefficient (r) ranged from 0.27 to 0.53. More correlations were found in 2012 than 2011. Similarly, significant correlations were found between greenhouse gases and theta at Psi=0 and Psi=-0.05. Moisture content (theta) held at Psi=0 positively correlated with CO2 (r=0.49), N2O (r=0.64) and negatively correlated with CH4 (r=-0.43) at p<0.05. Soil pore space indices and soil water (content and potential) seem to control greenhouse gases emissions in this soil. Inclusion of these controlling factors in models will certainly improve our understanding of the dynamics of greenhouse gases fluxes from soil.
  • Authors:
    • Pan, G.
    • Parton, W. J.
    • Ogle, S. M.
    • Cheng, K.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 3
  • Year: 2014
  • Summary: Understanding the potential for greenhouse gas (GHG) mitigation in agricultural lands is a critical challenge for climate change policy. This study uses the DAYCENT ecosystem model to predict GHG mitigation potentials associated with soil management in Chinese cropland systems. Application of ecosystem models, such as DAYCENT, requires the evaluation of model performance with data sets from experiments relevant to the climate and management of the study region. DAYCENT was evaluated with data from 350 cropland experiments in China, including measurements of nitrous oxide emissions (N2O), methane emissions (CH4), and soil organic carbon (SOC) stock changes. In general, the model was reasonably accurate with R2 values for model predictions vs. measurements ranging from 0.71 to 0.85. Modeling efficiency varied from 0.65 for SOC stock changes to 0.83 for crop yields. Mitigation potentials were estimated on a yield basis (Mg CO2-equivalent Mg−1Yield). The results demonstrate that the largest decrease in GHG emissions in rainfed systems are associated with combined effect of reducing mineral N fertilization, organic matter amendments and reduced-till coupled with straw return, estimated at 0.31 to 0.83 Mg CO2-equivalent Mg−1Yield. A mitigation potential of 0.08 to 0.36 Mg CO2-equivalent Mg−1Yield is possible by reducing N chemical fertilizer rates, along with intermittent flooding in paddy rice cropping systems.
  • Authors:
    • Deng, J.
    • Zhou, Z.
    • Wang, K.
    • Liu, C.
    • Zheng, X.
    • Cui, F.
  • Source: Biogeosciences Discussions
  • Volume: 10
  • Year: 2014
  • Summary: Contemporary agriculture is shifting from a single-goal to a multi-goal strategy, which in turn requires choosing best management practice (BMP) based on an assessment of the biogeochemical effects of management alternatives. The bottleneck is the capacity of predicting the simultaneous effects of different management practice scenarios on multiple goals and choosing BMP among scenarios. The denitrification-decomposition (DNDC) model may provide an opportunity to solve this problem. We validated the DNDC model (version 95) using the observations of soil moisture and temperature, crop yields, aboveground biomass and fluxes of net ecosystem exchange of carbon dioxide, methane, nitrous oxide (N2O), nitric oxide (NO) and ammonia (NH3) from a wheat-maize cropping site in northern China. The model performed well for these variables. Then we used this model to simulate the effects of management practices on the goal variables of crop yields, NO emission, nitrate leaching, NH3 volatilization and net emission of greenhouse gases in the ecosystem (NEGE). Results showed that no-till and straw-incorporated practices had beneficial effects on crop yields and NEGE. Use of nitrification inhibitors decreased nitrate leaching and N2O and NO emissions, but they significantly increased NH3 volatilization. Irrigation based on crop demand significantly increased crop yield and decreased nitrate leaching and NH3 volatilization. Crop yields were hardly decreased if nitrogen dose was reduced by 15% or irrigation water amount was reduced by 25 %. Two methods were used to identify BMP and resulted in the same BMP, which adopted the current crop cultivar, field operation schedules and full straw incorporation and applied nitrogen and irrigation water at 15 and 25% lower rates, respectively, than the current use. Our study indicates that the DNDC model can be used as a tool to assess biogeochemical effects of management alternatives and identify BMP.
  • 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.