• 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.
  • Authors:
    • Chi, S. Y.
    • Li, Z. J.
    • Li, N.
    • Wang, B. W.
    • Zhao, H. X.
    • Ning, T. Y.
    • Wang, Y.
    • Tian, S. Z.
  • Source: PLOS ONE
  • Volume: 8
  • Issue: 9
  • Year: 2013
  • Summary: Appropriate tillage plays an important role in mitigating the emissions of greenhouse gases (GHG) in regions with higher crop yields, but the emission situations of some reduced tillage systems such as subsoiling, harrow tillage and rotary tillage are not comprehensively studied. The objective of this study was to evaluate the emission characteristics of GHG (CH4 and N2O) under four reduced tillage systems from October 2007 to August 2009 based on a 10-yr tillage experiment in the North China Plain, which included no-tillage (NT) and three reduced tillage systems of subsoil tillage (ST), harrow tillage (HT) and rotary tillage (RT), with the conventional tillage (CT) as the control. The soil under the five tillage systems was an absorption sink for CH4 and an emission source for N2O. The soil temperature positive impacted on the CH4 absorption by the soils of different tillage systems, while a significant negative correlation was observed between the absorption and soil moisture. The main driving factor for increased N2O emission was not the soil temperature but the soil moisture and the content of nitrate. In the two rotation cycle of wheat-maize system (10/2007-10/2008 and 10/2008-10/2009), averaged cumulative uptake fluxes of CH4 under CT, ST, HT, RT and NT systems were approximately 1.67, 1.72, 1.63, 1.77 and 1.17 t ha(-1) year(-1), respectively, and meanwhile, approximately 4.43, 4.38, 4.47, 4.30 and 4.61 t ha(-1) year(-1) of N2O were emitted from soil of these systems, respectively. Moreover, they also gained 33.73, 34.63, 32.62, 34.56 and 27.54 t ha(-1) yields during two crop-rotation periods, respectively. Based on these comparisons, the rotary tillage and subsoiling mitigated the emissions of CH4 and N2O as well as improving crop productivity of a wheat-maize cropping system.
  • Authors:
    • Ju, X. T.
    • Su, F.
    • Huang, T.
    • Gao, B.
    • Jia, X. Y.
    • Wang, H. F.
  • Source: Acta Pedologica Sinica
  • Volume: 50
  • Issue: 6
  • Year: 2013
  • Summary: Illustrating mechanisms of N 2O generation in and emissions of CO 2 and CH 4 from the soil could help us design greenhouse gas mitigation strategies. An experiment was carried out in fields of acid red soil different in land use, i. e. vegetable garden, paddy field, tea garden and forest in Jinjing river region, Changsha, to study effects of application of carbon, nitrogen and nitrification inhibitor on N 2O, CO 2 and CH 4 emissions under constant temperature and soil moisture, using the static incubation-gas chromatograph method. Results show that less N 2O emission was observed from the acid red soil, low in pH, after application of N fertilizer; the addition of glucose stimulated N 2O emission from the soil applied with urea and from soil denitrification. Heterotrophic nitrification might be the main pathway of N 2O generation in acid red soil and nitrification inhibitor Dicyandiamide (DCD) had no significant effect on N 2O reduction in the acid red soil. In terms of total N 2O emission from the soil applied with N and C, the fields different in land use followed the order of tea garden > vegetable garden > paddy field > forest land. Extraneous organic carbon could significantly stimulate soil C0 2 emission from the four fields, showing an order of tea garden and paddy field > vegetable garden and forest land, but did not have much effect on CH 4 emission in all the four fields except paddy field.
  • Authors:
    • Zhao, Y-C.
    • Sun, W-X.
    • Tan, M-Z.
    • Xu, S-X.
    • Yu, D-S.
    • Shi, X-Z.
    • Wang, M-Y.
  • Source: Pedosphere
  • Volume: 23
  • Issue: 6
  • Year: 2013
  • Summary: The agricultural soil carbon pool plays an important role in mitigating greenhouse gas emission and understanding the soil organic carbon-climate-soil texture relationship is of great significance for estimating cropland soil carbon pool responses to climate change. Using data from 900 soil profiles, obtained from the Second National Soil Survey of China, we investigated the soil organic carbon (SOC) depth distribution in relation to climate and soil texture under various climate regimes of the cold northeast region (NER) and the warmer Huang-Huai-Hai region (HHHR) of China. The results demonstrated that the SOC content was higher in NER than in HHHR. For both regions, the SOC content at all soil depths had significant negative relationships with mean annual temperature (MAT), but was related to mean annual precipitation (MAP) just at the surface 0-20 cm. The climate effect on SOC content was more pronounced in NER than in HHHR. Regional differences in the effect of soil texture on SOC content were not found. However, the dominant texture factors were different. The effect of sand content on SOC was more pronounced than that of clay content in NER. Conversely, the effect of clay on SOC was more pronounced than sand in HHHR. Climate and soil texture jointly explained the greatest SOC variability of 49.0% (0-20 cm) and 33.5% (20-30 cm) in NER and HHHR, respectively. Moreover, regional differences occurred in the importance of climate vs. soil texture in explaining SOC variability. In NER, the SOC content of the shallow layers (0-30 cm) was mainly determined by climate factor, specifically MAT, but the SOC content of the deeper soil layers (30-100 cm) was more affected by texture factor, specifically sand content. In HHHR, all the SOC variability in all soil layers was predominantly best explained by clay content. Therefore, when temperature was colder, the climate effect became stronger and this trend was restricted by soil depth. The regional differences and soil depth influence underscored the importance of explicitly considering them in modeling long-term soil responses to climate change and predicting potential soil carbon sequestration.
  • Authors:
    • Dong, W. X.
    • Li, X. X.
    • Zhang, Y. M.
    • Ming, H.
    • Hu, C. S.
    • Wang, Y. Y.
    • Oenema, O.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 164
  • Issue: 1
  • Year: 2013
  • Summary: Agricultural soils are main sources and sinks of the greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). The source-sink function depends on soil characteristics, climate and management. Emission measurements usually quantify the net result of production, consumption and transport of these gases in the soil; they do not provide information about the depth distributions of the concentrations of these gases in the soil. Here we report on concentrations of CO2, CH4 and N2O in air of 300 cm deep soil profiles, at resolutions of 30-50 cm, over a full year. Gas samples were taken weekly in a long-term field experiment with an irrigated winter wheat-summer maize double cropping system, and four fertilizer N application rates (0, 200, 400 and 600 kg N ha(-1) year(-1)). The results showed distinct differences in CH4, CO2 and N2O concentrations profiles with soil depth. The concentrations of CO2 in soil air increased with soil depth and showed a seasonal pattern with relatively high concentrations in the warm and moist maize growing season and relatively low concentrations in the winter-wheat growing season. In contrast, CH4 concentrations decreased with depth, and did not show a distinct seasonal cycle. Urea application did not have a large effect on CH4 or CO2 concentrations, neither in the topsoil nor the subsoil. Concentrations of N2O responded to N fertilizer application and irrigation. Application of fertilizer strongly increased grain and straw yields of both winter wheat and summer maize, relatively to the control, but differences in yield between the treatments N200, N400 and N600 were not statistically significant. However, it significantly increased mean N2O concentrations peaks at basically all soil depths. Interestingly, concentrations of N2O increased almost instantaneously in the whole soil profile, which indicates that the soil had a relatively high diffusivity, despite compacted subsoil layers. In conclusion, the frequent measurements, at high depth resolutions, of concentrations of CH4, CO2 and N2O in soil air under a winter wheat-summer maize double crop rotation provide detailed insight into the production, consumption and transport of these gases in the soil. Concentrations of CH4, CO2 and N2O responded differently to management activities and weather conditions. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Malemela, M. P.
    • Chen, F.
    • Wang, F.
    • Zhang, M.
    • Zhang, H.
  • Source: Journal of Cleaner Production
  • Volume: 54
  • Year: 2013
  • Summary: Whether farmland serves as a carbon (C) source or sink depends on the balance of soil organic carbon (SOC) sequestration and greenhouse gas (GHG) emissions. Tillage practices critically affect the SOC concentration, SOC sequestration rate and soil carbon storage (SCS). The objective of this paper is to assess the tillage effects on SOC sequestration, SCS and C footprint. Tillage experiments were established on a double cropping system of winter wheat (Triticum aestivum L) and summer corn (Zea mays L) in the North China Plain since 2001 with three treatments: no tillage (NT), rotary tillage (RT) and conventional tillage (CT). In order to assess SOC sequestration efficiency under different tillage systems, SCS, SOC sequestration rate, hidden carbon cost (HCC), indexes of sustainability (I-s) and C productivity (CP) were computed in this study. Results showed that the SCS increased with years of residue retention. The SCS attained the highest degree in 2007, which was about 25%-30% higher than that in 2004. The net SOC sequestration rate was the highest in NT and lowest in cc, while HCC was lowest under NT and highest under CT. The value of Is for CT, RT and NT treatments was 1.46, 1.79 and 1.88, respectively, and that of CP was 11.02, 12.79 and 10.57, respectively. Therefore, it can be concluded that NT provides a good option for increasing SOC sequestration for agriculture in the North China Plain.
  • Authors:
    • Cassman, K. G.
    • Chen, X.
    • Wu, L.
    • Zhang, Y.
    • Lu, Y.
    • Norse, D.
    • Chadwick, D.
    • Powlson, D.
    • Ju, X.
    • He, P.
    • Dou, Z.
    • Zhang, W.
    • Zhang, F.
  • Source: Proceedings of the National Academy of Sciences of the United States of America
  • Volume: 110
  • Issue: 21
  • Year: 2013
  • Summary: Synthetic nitrogen (N) fertilizer has played a key role in enhancing food production and keeping half of the world's population adequately fed. However, decades of N fertilizer overuse in many parts of the world have contributed to soil, water, and air pollution; reducing excessive N losses and emissions is a central environmental challenge in the 21st century. China's participation is essential to global efforts in reducing N-related greenhouse gas (GHG) emissions because China is the largest producer and consumer of fertilizer N. To evaluate the impact of China's use of N fertilizer, we quantify the carbon footprint of China's N fertilizer production and consumption chain using life cycle analysis. For every ton of N fertilizer manufactured and used, 13.5 tons of CO2-equivalent (eq) (t CO2-eq) is emitted, compared with 9.7 t CO2-eq in Europe. Emissions in China tripled from 1980 [131 terrogram (Tg) of CO2-eq (Tg CO2-eq)] to 2010 (452 Tg CO2-eq). N fertilizer-related emissions constitute about 7% of GHG emissions from the entire Chinese economy and exceed soil carbon gain resulting from N fertilizer use by several-fold. We identified potential emission reductions by comparing prevailing technologies and management practices in China with more advanced options worldwide. Mitigation opportunities include improving methane recovery during coal mining, enhancing energy efficiency in fertilizer manufacture, and minimizing N overuse in field-level crop production. We find that use of advanced technologies could cut N fertilizer-related emissions by 20-63%, amounting to 102-357 Tg CO2-eq annually. Such reduction would decrease China's total GHG emissions by 2-6%, which is significant on a global scale.