• Authors:
    • Kurz, W. A.
    • Birdsey, R. A.
    • McConkey, B. G.
    • Dejong, B.
    • Heath, L. S.
    • West, T. O.
    • Wei, Y. X.
    • McGuire, A. D.
    • Stinson, G.
    • Turner, D. P.
    • Hayes, D. J.
    • Jacobson, A. R.
    • Huntzinger, D. N.
    • Pan, Y. D.
    • Post, W. M.
    • Cook, R. B.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 4
  • Year: 2012
  • Summary: We develop an approach for estimating net ecosystem exchange (NEE) using inventory-based information over North America (NA) for a recent 7-year period (ca. 2000-2006). The approach notably retains information on the spatial distribution of NEE, or the vertical exchange between land and atmosphere of all non-fossil fuel sources and sinks of CO 2, while accounting for lateral transfers of forest and crop products as well as their eventual emissions. The total NEE estimate of a -327252 TgC yr -1 sink for NA was driven primarily by CO 2 uptake in the Forest Lands sector (-248 TgC yr -1), largely in the Northwest and Southeast regions of the US, and in the Crop Lands sector (-297 TgC yr -1), predominantly in the Midwest US states. These sinks are counteracted by the carbon source estimated for the Other Lands sector (+218 TgC yr -1), where much of the forest and crop products are assumed to be returned to the atmosphere (through livestock and human consumption). The ecosystems of Mexico are estimated to be a small net source (+18 TgC yr -1) due to land use change between 1993 and 2002. We compare these inventory-based estimates with results from a suite of terrestrial biosphere and atmospheric inversion models, where the mean continental-scale NEE estimate for each ensemble is -511 TgC yr -1 and -931 TgC yr -1, respectively. In the modeling approaches, all sectors, including Other Lands, were generally estimated to be a carbon sink, driven in part by assumed CO 2 fertilization and/or lack of consideration of carbon sources from disturbances and product emissions. Additional fluxes not measured by the inventories, although highly uncertain, could add an additional -239 TgC yr -1 to the inventory-based NA sink estimate, thus suggesting some convergence with the modeling approaches.
  • Authors:
    • Angers, D. A.
    • Larney, F. J.
  • Source: Journal of Soil Science
  • Volume: 92
  • Issue: 1
  • Year: 2012
  • Summary: A basic tenet of sustainable soil management is that current human activities are not detrimental to future generations. Soils are degraded by natural events (erosion) or industrial activity. A prevalent feature of degraded or disturbed soils is lack of organic matter compared with adjacent undisturbed areas. Organic amendments, such as livestock manure, biosolids, pulp and paper mill by-products, wood residuals and crop residues, are produced in abundance in Canada and could be widely used in soil reclamation. Biosolids production is ~0.5 Tg yr -1(dry wt.); paper mill sludge generated in the province of Quebec was ~2 Tg (wet wt.) in 2002. This review paper examines mechanisms through which organic amendments affect soil properties (physical, chemical, biological) and describes the role of organic amendments in reclamation, with emphasis on amendment types and application rates for soil amelioration and biomass production. Single large applications of organic amendments can accelerate initial reclamation and lead to self-sustaining net primary productivity. Readily decomposable organic amendments may provide immediate, but transient, effects, whereas stable, less decomposable materials may provide longer-lasting effects. Using organic amendments for reclamation is mutually beneficial wherein waste products from agriculture, forestry and urban areas help other sectors meet their land reclamation goals.
  • Authors:
    • Angers, D. A.
    • Rochette, P.
    • Chantigny, M. H.
    • Pelster, D. E.
    • Rieux, C.
    • Vanasse, A.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 2
  • Year: 2012
  • Summary: The use of various animal manures for nitrogen (N) fertilization is often viewed as a viable replacement for mineral N fertilizers. However, the impacts of amendment type on N 2O production may vary. In this study, N 2O emissions were measured for 2 yr on two soil types with contrasting texture and carbon (C) content under a cool, humid climate. Treatments consisted of a no-N control, calcium ammonium nitrate, poultry manure, liquid cattle manure, or liquid swine manure. The N sources were surface applied and immediately incorporated at 90 kg N ha -1 before seeding of spring wheat ( Triticum aestivum L.). Cumulative N 2O-N emissions from the silty clay ranged from 2.2 to 8.3 kg ha -1 yr -1 and were slightly lower in the control than in the fertilized plots ( P=0.067). The 2-yr mean N 2O emission factors ranged from 2.0 to 4.4% of added N, with no difference among N sources. Emissions of N 2O from the sandy loam soil ranged from 0.3 to 2.2 kg N 2O-N ha -1 yr -1, with higher emissions with organic than mineral N sources ( P=0.015) and the greatest emissions with poultry manure ( P<0.001). The N 2O emission factor from plots amended with poultry manure was 1.8%, more than double that of the other treatments (0.3-0.9%), likely because of its high C content. On the silty clay, the yield-based N 2O emissions (g N 2O-N kg -1 grain yield N) were similar between treatments, whereas on the sandy loam, they were greatest when amended with poultry manure. Our findings suggest that, compared with mineral N sources, manure application only increases soil N 2O flux in soils with low C content.
  • Authors:
    • Schiff, S. L.
    • Venkiteswaran, J. J.
    • Snider, D. M.
    • Spoelstra, J.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 1
  • Year: 2012
  • Summary: The ability to use delta 18O values of nitrous oxide (N 2O) to apportion environmental emissions is currently hindered by a poor understanding of the controls on delta 18O-N 2O from nitrification (hydroxylamine oxidation to N 2O and nitrite reduction to N 2O). In this study fertilized agricultural soils and unfertilized temperate forest soils were aerobically incubated with different 18O/ 16O waters, and conceptual and mathematical models were developed to systematically explain the delta 18O-N 2O formed by nitrification. Modeling exercises used a set of defined input parameters to emulate the measured soil delta 18O-N 2O data (Monte Carlo approach). The Monte Carlo simulations implied that abiotic oxygen (O) exchange between nitrite (NO 2-) and H 2O is important in all soils, but that biological, enzyme-controlled O-exchange does not occur during the reduction of NO2a to N 2O (nitrifier-denitrification). Similarly, the results of the model simulations indicated that N 2O consumption is not characteristic of aerobic N 2O formation. The results of this study and a synthesis of the published literature data indicate that delta 18O-N 2O formed in aerobic environments is constrained between +13 per mil and +35 per mil relative to Vienna Standard Mean Ocean Water (VSMOW). N 2O formed via hydroxylamine oxidation and nitrifier-denitrification cannot be separated using delta 18O unless 18O tracers are employed. The natural range of nitrifier delta 18O-N 2O is discussed and explained in terms of our conceptual model, and the major and minor controls that define aerobically produced delta 18O-N 2O are identified. Despite the highly complex nature of delta 18O-N 2O produced by nitrification this delta 18O range is narrow. As a result, in many situations delta 18O values may be used in conjunction with delta 15N-N 2O data to apportion nitrifier- and denitrifier-derived N 2O. However, when biological O-exchange during denitrification is high and N 2O consumption is low, there may be too much overlap in delta 18O values to distinguish N 2O formed by these pathways.
  • Authors:
    • Kroetsch, D.
    • Vandenbygaart, A. J.
    • Gregorich, E. G.
    • Lobb, D.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 4
  • Year: 2012
  • Summary: Erosion influences the lateral and vertical distribution of soil in agricultural landscapes. A better understanding of the effects of erosion and redistribution on soil organic carbon (C) within croplands would improve our knowledge of how management practices may affect global C dynamics. In this study, the vertical and lateral distribution of soil organic C was characterized to evaluate the amounts and timescales of soil organic C movement, deposition and burial over the last 50 years in different agroecosystems across Canada. There was strong evidence that a substantial portion of eroded sediment and soil organic C was deposited as colluvium close to its source area, thereby burying the original topsoil. The deepest aggraded profile was in a potato field and contained over 70 cm of deposited soil indicating an accumulation rate of 152 Mg ha yr -1; aggraded profiles in other sites had soil deposition rates of 40-90 Mg ha -1 yr -1. The largest stock of soil organic C was 463 Mg ha -1 (to 60 cm depth) and soil C deposition ranged from about 2 to 4 Mg ha -1 yr -1 across all sites. A distinct feature observed in the aggraded profiles at every site was the presence of a large increase in soil organic C concentration near the bottom of the A horizon; the concentration of this C was greater than that at the soil surface. Compared to aggraded profiles, the SOC concentration in eroded profiles did not differ with depth, suggesting that dynamic replacement of soil organic C had occurred in eroded soils. A large amount of soil organic C is buried in depositional areas of Canadian croplands; mineralization of this stock of C appears to have been constrained since burial, but it may be vulnerable to future loss by management practices, land use change and a warming climate.
  • Authors:
    • Regetz, J.
    • Wolkovich, E. M.
    • O'Connor, M. I.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 7
  • Year: 2012
  • Summary: Understanding how species and ecosystems respond to climate change requires spatially and temporally rich data for a diverse set of species and habitats, combined with models that test and predict responses. Yet current study is hampered by the long-known problems of inadequate management of data and insufficient description of analytical procedures, especially in the field of ecology. Despite recent institutional incentives to share data and new data archiving infrastructure, many ecologists do not archive and publish their data and code. Given current rapid rates of global change, the consequences of this are extreme: because an ecological dataset collected at a certain place and time represents an irreproducible set of observations, ecologists doing local, independent research possess, in their file cabinets and spreadsheets, a wealth of information about the natural world and how it is changing. Although large-scale initiatives will increasingly enable and reward open science, we believe that change demands action and personal commitment by individuals - from students and PIs. Herein, we outline the major benefits of sharing data and analytical procedures in the context of global change ecology, and provide guidelines for overcoming common obstacles and concerns. If individual scientists and laboratories can embrace a culture of archiving and sharing we can accelerate the pace of the scientific method and redefine how local science can most robustly scale up to globally relevant questions.
  • Authors:
    • Yang, C.
    • Wang, H.
    • Lemke, R. L.
    • Zentner, R. P.
    • Campbell, C. A.
    • Liang, C.
    • Gan, Y.
  • Source: European Journal of Agronomy
  • Volume: 43
  • Issue: November
  • Year: 2012
  • Summary: Growing interest in environmental quality has provided a strong incentive to examine how farming practices affect agricultural products' carbon footprints (CF), an environmental quality indicator. This study determined (i) the CF of spring wheat (Triticurn aestivum L.) grown in different cropping systems over 25 years, and (ii) the effect of soil organic carbon (SOC) changes over years on wheat CF. Wheat was grown in four cropping systems: (a) fallow-wheat (FW), (b) fallow-wheat-wheat (FWW), (c) fallow-wheat-wheat-wheat-wheat-wheat (FWWWWW), and (d) continuous wheat (ContW), in replicated field plots in Saskatchewan, Canada. Wheat CF was calculated at a system level with measured variables coupled with modeling approaches. Over the 25-year period, the soil under the ContW system gained organic C of 1340 kg CO2 eq ha(-1) annually, or 38%. 55%, and 127% more than those gained in the FWWWWW, FWW, and FW systems, respectively. The SOC gain more than offset the greenhouse gas (GHG) emissions occurred during wheat production, leading to negative emission values at -742 kg CO2 eq ha(-1) annually for ContW, and -459, -404, and -191 kg CO2 eq ha(-1) for FWWWWW, FWW, and FW systems, respectively. Wheat in the ContW system produced the highest grain yield and gained highest SOC over the years, leading to the smallest (more negative) CF value at -0.441 kg CO2 eq kg(-1) of grain, significantly lower than the CF values from the three other systems (-0.102 to -0.116 kg CO2 eq kg(-1) of grain). Without considering the SOC gain in the calculation, wheat CF averaged 0.343 kg CO2 eq kg(-1) of grain and which did not differ among cropping systems. Wheat is the largest agricultural commodity in Saskatchewan, and the way the crop is produced has significant impacts on environmental quality, reflected by its carbon footprint. Cropping systems with decreased fallow frequency was shown to significantly enhance soil carbon gains over the years, increase annualized crop yields, and effectively lower the carbon footprint of this important commodity. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.
  • Authors:
    • Brandt, S. A.
    • Malhi, S. S.
    • Huang, G.
    • Liang, C.
    • Gan, Y.
    • Katepa-Mupondwa, F.
  • Source: The International Journal of Life Cycle Assessment
  • Volume: 17
  • Issue: 1
  • Year: 2012
  • Summary: Best agricultural practices can be adopted to increase crop productivity and lower carbon footprint of grain products. The aims of this study were to provide a quantitative estimate of the carbon footprint of selected oilseed crops grown on the semiarid northern Great Plains and to determine the effects of N fertilization and environments on the carbon footprint. Five oilseed crops, Brassica napus canola, Brassica rapa canola, Brassica juncea canola, B. juncea mustard, and Sinapis alba mustard, were grown under the N rates of 0, 25, 50, 100, 150, 200, and 250 kg N ha(-1) at eight environsites (location x year combinations) in Saskatchewan, Canada. Straw and root decomposition and various production inputs were used to calculate greenhouse gas emissions and carbon footprints. Emissions from the production, transportation, storage, and delivery of N fertilizer to farm gates accounted for 42% of the total greenhouse gas emissions, and the direct and indirect emission from the application of N fertilizer in oilseed production added another 31% to the total emission. Emissions from N fertilization were nine times the emission from the use of pesticides and 11 times that of farming operations. Straw and root decomposition emitted 120 kg CO(2)eq ha(-1), contributing 10% to the total emission. Carbon footprint increased slightly as N rates increased from 0 to 50 kg N ha(-1), but as N rates increased from 50 to 250 kg N ha(-1), carbon footprint increased substantially for all five oilseed crops evaluated. Oilseeds grown at the humid Melfort site emitted 1,355 kg CO(2)eq ha(-1), 30% greater than emissions at the drier sites of Scott and Swift Current. Oilseeds grown at Melfort had their carbon footprint of 0.52 kg CO(2)eq kg(-1) of oilseed, 45% greater than that at Scott (0.45 kg CO(2)eq kg(-1) of oilseed), and 25% greater than that at Swift Current (0.45 kg CO(2)eq kg(-1) of oilseed). Carbon footprint of oilseeds was a function of the rate of N fertilizer, and the intensity of the functionality varied between environments. Key to lower carbon footprint in oilseeds is to improve N management practices.
  • Authors:
    • Niu, J.
    • Malhi, S. S.
    • May, W.
    • Liang, C.
    • Gan, Y.
    • Wang, X.
  • Source: The International Journal of Life Cycle Assessment
  • Volume: 17
  • Issue: 5
  • Year: 2012
  • Summary: Carbon footprint of field crops can be lowered through improved cropping practices. The objective of this study was to determine the carbon footprint of spring barley ( L.) in relation to various preceding oilseed crops that were fertilized at various rates of inorganic N the previous years. System boundary was from cradle-to-farm gate. Canola-quality mustard ( L.), canola ( L.), sunflower ( L.), and flax ( L.) were grown under the N fertilizer rates of 10, 30, 70, 90, 110, 150, and 200 kg N ha(-1) the previous year, and spring barley was grown on the field of standing oilseed stubble the following year. The study was conducted at six environmental sites; they were at Indian Head in 2005, 2006 and 2007, and at Swift Current in 2004, 2005 and 2006, Saskatchewan, Canada. On average, barley grown at humid Indian Head emitted greenhouse gases (GHGs) of 1,003 kg CO(2)eq ha(-1), or 53% greater than that at the drier Swift Current site. Production and delivery of fertilizer N to farm gate accounted for 26% of the total GHG emissions, followed by direct and indirect emissions of 28% due to the application of N fertilizers to barley crop. Emissions due to N fertilization were 26.6 times the emission from the use of phosphorous, 5.2 times the emission from pesticides, and 4.2 times the emission from various farming operations. Decomposition of crop residues contributed emissions of 173 kg CO(2)eq ha(-1), or 19% of the total emission. Indian Head-produced barley had significantly greater grain yield, resulting in about 11% lower carbon footprint than Swift Current-produced barley (0.28 vs. 0.32 kg CO(2)eq kg(-1) of grain). Emissions in the barley production was a linear function of the rate of fertilizer N applied to the previous oilseed crops due to increased emissions from crop residue decomposition coupled with higher residual soil mineral N. The key to lower the carbon footprint of barley is to increase grain yield, make a wise choice of crop types, reduce N inputs to crops grown in the previous and current growing seasons, and improved N use efficiency.
  • Authors:
    • Wagner-Riddle, C.
    • Maas, S. E.
    • Amiro, B. D.
    • Tenuta, M.
    • Glenn, A. J.
  • Source: Agricultural and Forest Meteorology
  • Volume: 166
  • Issue: December
  • Year: 2012
  • Summary: Agricultural soils are a significant anthropogenic source of nitrous oxide (N2O) to the atmosphere. Despite likely having large emissions of N2O, there are no continuous multi-year studies of emissions from poorly drained floodplain soil. In the present study, the micrometeorological flux of N2O (E-N) was measured over three years (2006-2008) in a maize (Zea mays L.)/faba (Vicia faba minor L.)/spring-wheat (Triticum aestivum L) rotation in the Red River Valley, Manitoba, Canada on a gleyed humic verticol soil. Comparison of newly established reduced and intensive tillage treatments showed no difference in F-N within the constraints of the high variability between duplicate plots. The annual gap-filled Sigma F-N across tillage treatments was 5.5, 1.4, and 4.3 kg N ha(-1) in the maize, faba, and spring-wheat crop years, respectively. Emissions from fertilizer N addition and soil thaw the following spring was responsible for the greater Sigma F-N in the maize and spring-wheat years. Using four approaches to approximate background Sigma F-N resulted in estimates of 3.5-3.8% and 1.4-1.8% of applied fertilizer N emitted as N2O for the maize and spring-wheat crops, respectively. The CO2 global warming potential equivalent of Sigma F-N over the three study years was an emission of 5.4 Mg CO2-equiv. ha(-1) which adds to the previously determined C balance emission of 11.6 Mg CO2-equiv. ha(-1). (c) 2012 Elsevier B.V. All rights reserved.