• Authors:
    • Robertson, G.
    • Ruan, L.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 8
  • Year: 2013
  • Summary: Around 4.4 millionha of land in USDA Conservation Reserve Program (CRP) contracts will expire between 2013 and 2018 and some will likely return to crop production. No-till (NT) management offers the potential to reduce the global warming costs of CO2, CH4, and N2O emissions during CRP conversion, but to date there have been no CRP conversion tillage comparisons. In 2009, we converted portions of three 9-21ha CRP fields in Michigan to conventional tillage (CT) or NT soybean production and reserved a fourth field for reference. Both CO2 and N2O fluxes increased following herbicide application in all converted fields, but in the CT treatment substantial and immediate N2O and CO2 fluxes occurred after tillage. For the initial 201-day conversion period, average daily N2O fluxes (g N2O-Nha(-1)d(-1)) were significantly different in the order: CT (47.5 +/- 6.31, n=6)>> NT (16.7 +/- 2.45, n=6)>> reference (2.51 +/- 0.73, n=4). Similarly, soil CO2 fluxes in CT were 1.2 times those in NT and 3.1 times those in the unconverted CRP reference field. All treatments were minor sinks for CH4 (-0.69 +/- 0.42 to -1.86 +/- 0.37g CH4-Cha(-1)d(-1)) with no significant differences among treatments. The positive global warming impact (GWI) of converted soybean fields under both CT (11.5 Mg CO(2)eha(-1)) and NT (2.87 Mg CO(2)eha(-1)) was in contrast to the negative GWI of the unconverted reference field (-3.5 Mg CO(2)eha(-1)) with on-going greenhouse gas (GHG) mitigation. N2O contributed 39.3% and 55.0% of the GWI under CT and NT systems with the remainder contributed by CO2 (60.7% and 45.0%, respectively). Including foregone mitigation, we conclude that NT management can reduce GHG costs by 60% compared to CT during initial CRP conversion.
  • Authors:
    • Sainju, U. M.
  • Source: Agronomy journal
  • Volume: 105
  • Issue: 5
  • Year: 2013
  • Summary: Management practices can reduce N losses through N leaching and N2O emissions (a greenhouse gas) by increasing soil N storage. The effects of tillage, cropping sequence, and N fertilization rate were studied on N contents in dryland crop biomass, surface residue, and soil at the 0- to 120-cm depth, and estimated N balance from 2006 to 2011 in eastern Montana. Treatments were no-till continuous malt barley (Hordeum vulgaris L.) (NTCB), no-till malt barley-pea (Pisum sativum L.) (NTB-P), no-till malt barley-fallow (NTB-F), and conventional till malt barley-fallow (CTB-F), each with 0 to 120 kg N ha(-1). Biomass and surface residue N increased with increased N rate and were greater in NTB-P or NTCB than CTB-F and NTB-F in all years, except in 2006 and 2011. Soil total nitrogen (STN) at 0 to 60 cm decreased from 2006 to 2011 at 254 kg N ha(-1) yr(-1), regardless of treatments. At most depths, soil NH4-N content varied, but NO3-N content was greater in CTB-F than other cropping sequences. Estimated N balance was greater in NTB-P with 40 kg N ha(-1) than other treatments. No-till continuous cropping increased biomass and surface residue N, but conventional till crop-fallow increased soil available N. Because of increased soil N storage and reduced N requirement to malt barley, NTB-P with 40 kg N ha(-1) may reduce N loss due to leaching, volatilization, and denitrification compared to other treatments.
  • 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:
    • 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:
    • Fox, T. R.
    • Seiler, J. R.
    • Stovall, J. P.
  • Source: Plant and Soil
  • Volume: 363
  • Issue: 1-2
  • Year: 2013
  • Summary: We investigated whether changes in respiratory C fluxes, soil CO2 efflux, or root exudate quantity or quality explained differences in growth rates between closely related clones of Pinus taeda (L.). A factorial design with two clones, fertilized and control treatments, and four sequential harvests was installed in a greenhouse for 121 days. The two clones did show significant differences in respiratory C fluxes, soil CO2 efflux, and root exudation quantity and quality. While the clones also differed in growth rates, the C fluxes assessed in this paper did not explain how seedlings were able to allocate more C to stem growth in the months following fertilizer application. Changes in root exudation were not consistent with reduced heterotrophic soil CO2 efflux, which does not appear to be a plant-mediated process. These results indicate that if single genotypes are deployed over large land areas in plantations, dramatic differences between clonal plant-soil interactions may require consideration in ecosystem C budgets. Further, the range of belowground fluxes observed implies that genotype-specific C allocation may make some clones better able to exploit a given resource environment than others.
  • Authors:
    • Suddick, E. C.
    • Six, J.
  • Source: Science of the Total Environment
  • Volume: 465
  • Year: 2013
  • Summary: Agricultural soils are responsible for emitting large quantities of nitrous oxide (N2O). The controlled incomplete thermal decomposition of agricultural wastes to produce biochar, once amended to soils, have been hypothesized to increase crop yield, improve soil quality and reduce N2O emissions. To estimate crop yields, soil quality parameters and N2O emissions following the incorporation of a high temperature (900 degrees C) walnut shell (HTWS) biochar into soil, a one year field campaign with four treatments (control (CONT), biochar (B), compost (COM), and biochar+compost (B+C)) was conducted in a small scale vegetable rotation system in Northern California. Crop yields from five crops (lettuce, winter cover crop, lettuce, bell pepper and Swiss chard) were determined; there were no significant differences in yield between treatments. Biochar amended soils had significant increases in % total carbon (C) and the retention of potassium (K) and calcium (Ca). Annual cumulative N2O fluxes were not significantly different between the four treatments with emissions ranging from 0.91 to 1.12 kg N2O-N ha(-1) yr(-1). Distinct peaks of N2O occurred upon the application of N fertilizers and the greatest mean emissions, ranging from 67.04 to 151.41 g N2O-N ha(-1) day(-1), were observed following the incorporation of the winter cover crop. In conclusion, HTWS biochar application to soils had a pronounced effect on the retention of exchangeable cations such as K and Ca compared to un-amended soils and composted soils, which in turn could reduce leaching of these plant available cations and could thus improve soils with poor nutrient retention. However, HTWS biochar additions to soil had neither a positive or negative effect on crop yield nor cumulative annual emissions of N2O.
  • Authors:
    • Liu, S. G.
    • Tan, Z. X.
  • Source: Applied and Environmental Soil Science
  • Volume: 2013
  • Issue: 2013
  • Year: 2013
  • Summary: Terrestrial carbon (C) sequestration through optimizing land use and management is widely considered a realistic option to mitigate the global greenhouse effect. But how the responses of individual ecosystems to changes in land use and management are related to baseline soil organic C (SOC) levels still needs to be evaluated at various scales. In this study, we modeled SOC dynamics within both natural and managed ecosystems in North Dakota of the United States and found that the average SOC stock in the top 20 cm depth of soil lost at a rate of 450 kg C ha -1 yr -1 in cropland and 110 kg C ha -1 yr -1 in grassland between 1971 and 1998. Since 1998, the study area had become a SOC sink at a rate of 44 kg C ha -1 yr -1. The annual rate of SOC change in all types of lands substantially depends on the magnitude of initial SOC contents, but such dependency varies more with climatic variables within natural ecosystems and with management practices within managed ecosystems. Additionally, soils with high baseline SOC stocks tend to be C sources following any land surface disturbances, whereas soils having low baseline C contents likely become C sinks following conservation management.
  • 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:
    • Srinivasan, R.
    • Williams, J. R.
    • Arnold, J. G.
    • Izaurralde, R. C.
    • Zhang, X.
  • Source: Science of the Total Environment
  • Volume: 463-464
  • Year: 2013
  • Summary: Climate change is one of the most compelling modern issues and has important implications for almost every aspect of natural and human systems. The Soil and Water Assessment Tool (SWAT) model has been applied worldwide to support sustainable land and water management in a changing climate. However, the inadequacies of the existing carbon algorithm in SWAT limit its application in assessing impacts of human activities on CO2 emission, one important source of greenhouse gasses (GHGs) that traps heat in the earth system and results in global warming. In this research, we incorporate a revised version of the CENTURY carbon model into SWAT to describe dynamics of soil organic matter (SOM)-residue and simulate land-atmosphere carbon exchange. We test this new SWAT-C model with daily eddy covariance (EC) observations of net ecosystem exchange (NEE) and evapotranspiration (ET) and annual crop yield at six sites across the U.S. Midwest. Results show that SWAT-C simulates well multi-year average NEE and ET across the spatially distributed sites and capture the majority of temporal variation of thesetwo variables at a daily time scale at each site. Our analyses also reveal that performance of SWAT-C is influenced by multiple factors, such as crop management practices (irrigated vs. rainfed), completeness and accuracy of input data, crop species, and initialization of state variables. Overall, the new SWAT-C demonstrates favorable performance for simulating land-atmosphere carbon exchange across agricultural sites with different soils, climate, and management practices. SWAT-C is expected to serve as a useful tool for including carbon flux into consideration in sustainable watershed management under a changing climate. We also note that extensive assessment of SWAT-C with field observations is required for further improving the model and understanding potential uncertainties of applying it across large regions with complex landscapes.
  • Authors:
    • Hyland, C.
    • Enders, A.
    • Hanley, K.
    • Lehmann, J.
    • Gueerena, D.
    • Riha, S.
  • Source: PLANT AND SOIL
  • Volume: 365
  • Issue: 1-2
  • Year: 2013
  • Summary: Biochar additions to tropical soils have been shown to reduce N leaching and increase N use efficiency. No studies exist verifying reduced N leaching in field experiments on temperate agricultural soils or identifying the mechanism for N retention. Biochar derived from maize stover was applied to a maize cropping system in central New York State at rates of 0, 1, 3, 12, and 30 t ha(-1) in 2007. Secondary N fertilizer was added at 100, 90, 70, and 50 % of the recommended rate (108 kg N ha(-1)). Nitrogen fertilizer enriched with (15) N was applied in 2009 to the 0 and 12 t ha(-1) of biochar at 100 and 50 % secondary N application. Maize yield and plant N uptake did not change with biochar additions (p > 0.05; n = 3). Less N (by 82 %; p < 0.05) was lost after biochar application through leaching only at 100 % N fertilization. The reason for an observed 140 % greater retention of applied (15) N in the topsoil may have been the incorporation of added (15) N into microbial biomass which increased approximately three-fold which warrants further research. The low leaching of applied fertilizer (15) N (0.42 % of applied N; p < 0.05) and comparatively high recovery of applied (15) N in the soil (39 %) after biochar additions after one cropping season may also indicate greater overall N retention through lower gaseous or erosion N losses with biochar. Addition of biochar to fertile soil in a temperate climate did not improve crop growth or N use efficiency, but increased retention of fertilizer N in the topsoil.