• Authors:
    • Abney, T. S.
    • Vyn, T. J.
    • Stott, D. E.
    • Gal, A.
    • Omonode, R. A.
  • Source: Soil Science Society of America Journal
  • Volume: 70
  • Issue: 2
  • Year: 2006
  • Summary: For various reasons, North American crop farmers are more likely to practice limited-duration no-till than continuous no-till (NT). Little is known about effects of short-term no-till (ST-NT) on organic C and total N relative to NT and conventional-till systems. A field experiment was initiated in 1980 to study the effects of NT, chisel plow (CP), and moldboard plow in continuous corn (CC; Zeamays L.) and soybean (Glycinemax. L.)-corn (SC) rotations on dark prairie soil. In 1996, the moldboard treatments were split into a ST-NT subplot and an intermittently chisel-plowed (STI-CP) subplot that was chiseled only before corn. In 2003, soil samples were taken incrementally to the 1.0-m depth from NT, CP, ST-NT, and STI-CP plots. Soil C and N accumulation was unaffected by rotation system at any depth interval. Tillage treatments significantly affected soil C and N concentrations only in the upper 50 cm. On an equivalent soil mass basis, C storage to 1.0 m after 24 yr totaled 151 Mg ha21 in continuous NT, but just 108 Mg ha21 in continuous CP. Short-term no-till and STI-CP systems resulted in 26 and 21 Mg ha21, respectively, more soil C than CP. Total N storage was similar for NT and ST-NT systems, but was significantly lower (4 Mg ha21 less) with CP. Our results suggest that the combination of moldboard plowing (17 yr) followed by short-term (6-7 yr) no-till or intermittent chisel was generally superior to continuous chisel plowing (24 yr) in soil C and N contents.
  • Authors:
    • Boyles, S. B.
    • Nelson, R. G.
    • Rice, C. W.
    • Williams, J. R.
    • Pendell, D. L.
  • Source: Journal of Environmental Quality
  • Volume: 35
  • Issue: 4
  • Year: 2006
  • Summary: This study examined the economic potential of no-tillage versus conventional tillage to sequester soil carbon by using two rates of commercial N fertilizer or beef cattle manure for continuous corn (Zea mays L.) production. Yields, input rates, field operations, and prices from an experiment were used to simulate a distribution of net returns for eight production systems. Carbon release values from direct, embodied, and feedstock energies were estimated for each system, and were used with soil carbon sequestration rates from soil tests to determine the amount of net carbon sequestered by each system. The values of carbon credits that provide an incentive for managers to adopt production systems that sequester carbon at greater rates were derived. No-till systems had greater annual soil carbon gains, net carbon gains, and net returns than conventional tillage systems. Systems that used beef cattle manure had greater soil carbon gains and net carbon gains, but lower net returns, than systems that used commercial N fertilizer. Carbon credits would be needed to encourage the use of manure-fertilized cropping systems.
  • Authors:
    • Kimble, J. M.
    • McCarty, G. W.
    • Follett, R. F.
    • Reeves, J. B.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 37
  • Issue: 15-20
  • Year: 2006
  • Summary: The objective of this study was to compare mid-infrared (MIR) an near-infrared (NIR) spectroscopy (MIRS and NIRS, respectively) not only to measure soil carbon content, but also to measure key soil organic C (SOC) fractions and the delta13C in a highly diverse set of soils while also assessing the feasibility of establishing regional diffuse reflectance calibrations for these fractions. Two hundred and thirty-seven soil samples were collected from 14 sites in 10 western states (CO, IA, MN, MO, MT, ND, NE, NM, OK, TX). Two subsets of these were examined for a variety of C measures by conventional assays and NIRS and MIRS. Biomass C and N, soil inorganic C (SIC), SOC, total C, identifiable plant material (IPM) (20x magnifying glass), the ratio of SOC to the silt+clay content, and total N were available for 185 samples. Mineral-associated C fraction, delta13C of the mineral associated C, delta13C of SOC, percentage C in the mineral-associated C fraction, particulate organic matter, and percentage C in the particulate organic matter were available for 114 samples. NIR spectra (64 co-added scans) from 400 to 2498 nm (10-nm resolution with data collected every 2 nm) were obtained using a rotating sample cup and an NIRSystems model 6500 scanning monochromator. MIR diffuse reflectance spectra from 4000 to 400 cm-1 (2500 to 25,000 nm) were obtained on non-KBr diluted samples using a custom-made sample transport and a Digilab FTS-60 Fourier transform spectrometer (4-cm-1 resolution with 64 co-added scans). Partial least squares regression was used with a one-out cross validation to develop calibrations for the various analytes using NIR and MIR spectra. Results demonstrated that accurate calibrations for a wide variety of soil C measures, including measures of delta13C, are feasible using MIR spectra. Similar efforts using NIR spectra indicated that although NIR spectrometers may be capable of scanning larger amounts of samples, the results are generally not as good as achieved using MIR spectra.
  • Authors:
    • Waddell, J.
    • Caesar-Tonthat, T.
    • Lenssen, A.
    • Sainju, U. M.
  • Source: Soil Science Society of America Journal
  • Volume: 70
  • Issue: 2
  • Year: 2006
  • Summary: Sustainable management practices are needed to enhance soil productivity in degraded dryland soils in the northern Great Plains. We examined the effects of two tillage practices [conventional till (CT) and no-till (NT)], five crop rotations [continuous spring wheat (Triticum aestivum L.) (CW), spring wheat-fallow (W-F), spring wheat-lentil (Lens culinaris Medic.) (W-L), spring wheat-spring wheat-fallow (W-W-F), and spring wheat-pea (Pisum sativum L.)-fallow (W-P-F)], and a Conservation Reserve Program (CRP) on plant biomass returned to the soil, residue C and N, and soil organic C (SOC), soil total N (STN), and particulate organic C and N (POC and PON) at the 0- to 20-cm depth. A field experiment was conducted in a mixture of Scobey clay loam (fine, smectitic, frigid Aridic Argiustolls) and Kevin clay loam (fine-loamy, mixed, superactive, frigid Aridic Argiustolls) from 1998 to 2003 near Havre, MT. Mean annualized plant biomass returned to the soil from 1998 to 2003 was greater in W-F (2.02 Mg ha-1) than in W-L and W-W-F, regardless of tillage. In 2004, residue cover was greater in CW (60%) than in other rotations, except in W-W-F. Residue amount and C and N contents were greater in NT with CW (2.47 Mg ha-1 and 963 and 22 kg ha-1, respectively) than in NT with W-L and CT with other crop rotations. The POC at 0 to 5 cm was greater in W-W-F and W-P-F (2.1-2.2 Mg ha-1) than in W-L. Similarly, STN at 5 to 20 cm was greater in CT with W-L (2.21 Mg ha-1) than in other treatments, except in NT with W-W-F. Reduced tillage and increased cropping intensity, such as NT with CW and W-L, conserved C and N in dryland soils and crop residue better than the traditional practice, CT with W-F, and their contents were similar to or better than in CRP planting.
  • Authors:
    • Parrish, D. J.
    • Ebinger, M. H.
    • Lal, R.
    • Sartori, F.
  • Source: Critical Reviews in Plant Sciences
  • Volume: 25
  • Issue: 5
  • Year: 2006
  • Summary: Energy crops are fast-growing species whose biomass yields are dedicated to the production of more immediately usable energy forms, such as liquid fuels or electricity. Biomass-based energy sources can offset, or displace, some amount of fossil-fuel use. Energy derived from biomass provides 2 to 3% of the energy used in the U.S.A.; but, with the exception of corn-(Zea mays L.)-to-ethanol, very little energy is currently derived from dedicated energy crops. In addition to the fossil-fuel offset, energy cropping might also mitigate an accentuated greenhouse gas effect by causing a net sequestration of atmospheric C into soil organic C (SOC). Energy plantations of short-rotation woody crops (SRWC) or herbaceous crops (HC) can potentially be managed to favor SOC sequestration. This review is focused primarily on the potential to mitigate atmospheric CO2 emissions by fostering SOC sequestration in energy cropping systems deployed across the landscape in the United States. We know that land use affects the dynamics of the SOC pool, but data about spatial and temporal variability in the SOC pool under SRWC and HC are scanty due to lack of well-designed, long-term studies. The conventional methods of studying SOC fluxes involve paired-plot designs and chronosequences, but isotopic techniques may also be feasible in understanding temporal changes in SOC. The rate of accumulation of SOC depends on land-use history, soil type, vegetation type, harvesting cycle, and other management practices. The SOC pool tends to be enhanced more under deep-rooted grasses, N-fixers, and deciduous species. Carbon sequestration into recalcitrant forms in the SOC pool can be enhanced with some management practices (e.g., conservation tillage, fertilization, irrigation); but those practices can carry a fossil-C cost. Reported rates of SOC sequestration range from 0 to 1.6 Mg C ha(-1) yr(-1) under SRWC and 0 to 3 Mg C ha(-1) yr(-1) under HC. Production of 5 EJ of electricity from energy crops-a perhaps reasonable scenario for the U.S.A.-would require about 60 Mha. That amount of land is potentially available for conversion to energy plantations in the U.S.A. The land so managed could mitigate C emissions (through fossil C not emitted and SOC sequestered) by about 5.4 Mg C ha(-1) yr(-1). On 60 Mha, that would represent 324 Tg C yr(-1)-a 20% reduction from current fossil-fuel CO2 emissions. Advances in productivity of fast-growing SRWC and HC species suggest that deployment of energy cropping systems could be an effective strategy to reduce climate-altering effects of anthropogenic CO2 emissions and to meet global policy commitments.
  • Authors:
    • VandenBygaart, A. J.
  • Source: Canadian Journal of Soil Science
  • Volume: 86
  • Issue: 3
  • Year: 2006
  • Summary: The distribution of soil organic carbon (SOC) in the landscape is governed by multiple factors and processes occurring at multiple scales. Thus, an understanding of landscape processes and pedology should aid in designing approaches to study SOC stock changes. Numerous factors affect distribution of SOC in the landscape at varying spatial and temporal scales. Each of these is summarized to set the stage for outlining a proposed approach to monitoring SOC in the agricultural landscape. Many tools are used to assess the variability of soil properties at varying spatial scales. Pedological knowledge and interpretation of landscape processes can be used to understand the spatial distribution of SOC in the landscape. I show that semi-variograms and the minimum detectable difference may be of limited value in deriving a universal approach to assess SOC change. Issues to be considered or resolved before initiating a monitoring system include depth of sampling and influence of management, compositing and sub-sampling, changes in bulk density, landscape effects and SOC dynamics. After considering these issues, I propose an approach to monitor SOC stock change in agroecosystems, acknowledging that any methodology likely cannot be strictly and universally applicable. The approach considers issues such as location, plot layout, and experimental and statistical design. Such an approach, derived from a landscape and pedology perspective, may make the measurement and verification of SOC at varying scales a less daunting task.
  • Authors:
    • Angers, D. A.
    • VandenBygaart, A. J.
  • Source: Canadian Journal of Soil Science
  • Volume: 86
  • Issue: 3
  • Year: 2006
  • Summary: In response to Kyoto Protocol commitments, countries can elect agricultural carbon sinks to offset emissions from other sectors, but they need to verify soil organic carbon (SOC) stock change. We summarize issues we see as barriers to obtaining accurate measures of SOC change, including: soil depth, bulk density and equivalent soil mass, representation of landscape components, experimental design, and the equilibrium status of the SOC. If the entire plow depth is not considered, rates of SOC storage under conservation compared with conventional tillage can be overstated. Bulk density must be measured to report SOC stock on an area basis. More critical still is the need to report SOC stock on an equivalent mass basis to normalize the effects of management on bulk deisity. Most experiments comparing SOC under differing management have been conducted in small, flat research plots. Although results obtained from these long-term experiments have been useful to develop and validate SOC prediction models, they do not adequately consider landscape effects. Traditional agronomic experimental designs can be inefficient for assessing small changes in SOC stock within large spatial variability. Sampling designs are suggested to improve statistical power and sensitivity in detecting changes in SOC stocks over short time periods.
  • Authors:
    • Jakas, M. C. Q.
    • Rosenberg, N. J.
    • McGill, W. B.
    • Williams, J. R.
    • Izaurralde, R. C.
  • Source: Ecological Modelling
  • Volume: 192
  • Issue: 3-4
  • Year: 2006
  • Summary: Soil carbon sequestration (SCS) has emerged as a technology with significant potential to help stabilize atmospheric CO2 concentrations and thus reduce the threat of global warming. Methods and models are needed to evaluate and recommend SCS practices based on their effects on carbon dynamics and environmental quality. Environment Policy Integrated Climate (EPIC) is a widely used and tested model for simulating many agroecosystem processes including plant growth, crop yield, tillage, wind and water erosion, runoff, soil density, and leaching. Here we describe new C and N modules developed in EPIC built on concepts from the Century model to connect the simulation of soil C dynamics to crop management, tillage methods, and erosion processes. The added C and N routines interact directly with soil moisture, temperature, erosion, tillage, soil density, leaching, and translocation functions in EPIC. Equations were also added to describe the effects of soil texture on soil C stabilization. Lignin concentration is modeled as a sigmoidal function of plant age. EPIC was tested against data from a conservation reserve program (CRP) 6-year experiment at five sites in three U.S. Great Plains states and a 61-year long-term agronomic experiment near Breton, Canada. Mean square deviations (MSD) calculated for CRP sites were less than 0.01 (kg C m(-2))(2), except for one site where it reached 0.025 (kg C m(-2))(2). MSD values in the 61-year experiment ranged between 0.047 and 0.077 (kg C m(-2))(2). The version of the EPIC model presented and tested here contains the necessary algorithms to simulate SCS and improve understanding of the interactions among soil erosion, C dynamics, and tillage. A strength of the model as tested is its ability to explain the variability in crop production, C inputs and SOC and N cycling over a wide range of soil, cropping and climatic conditions over periods from 6 to 61 years. For example, at the Breton site over 61 years, EPIC accounted for 69% of the variability in grain yields, 89% of the variability in C inputs and 91% of the variability in SOC content in the top 15 cm. Continued development is needed in understanding why it overpredicts at low SOC and underpredicts at high SOC. Possibilities now exist to connect the C and N cycling parts of EPIC to algorithms to describe denitrification as driven by C metabolism and oxygen availability. (c) 2005 Elsevier B.V. All rights reserved.
  • Authors:
    • Rochette, P.
    • Pattey, E.
    • Newlands, N.
    • McAllister, T. A.
    • McGinn, S. M.
    • Masse, D.
    • Lemke, R.
    • Helgason, B. L.
    • Gregorich, E. G.
    • Gibb, D. J.
    • Ellert, B. H.
    • Dyer, J. A.
    • Desjardins, R. L.
    • Bolinder, M.
    • Boehm, M.
    • Angers, D. A.
    • Janzen, H. H.
    • Smith, W.
    • VandenBygaart, A. J.
    • Wang, H.
  • Source: Canadian Journal of Soil Science
  • Volume: 86
  • Issue: 3
  • Year: 2006
  • Summary: Greenhouse gas emissions from farms can be suppressed in two ways: by curtailing the release of these gases (especially N2O and CH4), and by storing more carbon in soils, thereby removing atmospheric COT But most practices have multiple interactive effects on emissions throughout a farm. We describe an approach for identifying practices that best reduce net, whole-farm emissions. We propose to develop a "Virtual Farm", a series of interconnected algorithms that predict net emissions from flows of carbon, nitrogen, and energy. The Virtual Farm would consist of three elements: descriptors, which characterize the farm; algorithms, which calculate emissions from components of the farm; and an integrator, which links the algorithms to each other and the descriptors, generating whole-farm estimates. Ideally, the Virtual Farm will be: boundary-explicit, with single farms as the fundamental unit; adaptable to diverse farm types; modular in design; simple and transparent; dependent on minimal, attainable inputs; internally consistent; compatible with models developed elsewhere; and dynamic ("seeing" into the past and the future). The Virtual Farm would be constructed via two parallel streams - measurement and modeling - conducted iteratively. The understanding built into the Virtual Farm may eventually be applied to issues beyond greenhouse gas mitigation.
  • Authors:
    • Lal, R.
    • Jarecki, M. K.
  • Source: Soil Science
  • Volume: 171
  • Issue: 3
  • Year: 2006
  • Summary: Accelerating soil erosion, leading to loss of the surface soil, is a common occurrence in croplands on undulating terrain. Yet the impact of erosion and reclamation measure on emission of greenhouse gases (GHG) is not known. Three predominant GHG emitted from cropland are as follows: carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). The most abundant GHG is CO2, but N2O and CH4 are also important, with global warming potentials (GWP) of 297 and 23, respectively. The objectives of this study were to evaluate the effect of imitated soil erosion on gaseous emission, to determine the effects of application of wheat (Triticum aestivum) residue mulch and swine manure and soybean (Glycine max) residue compost as soil-restorative measures on fluxes of CO2, N2O, and CH4 from uncropped, undisturbed, and desurfaced plots, and to determine relations between GHG fluxes and air and soil temperature, precipitation, and soil-moisture regimes. The microplot (2 X 2 m) experiment was established in 2002 on a Crosby silt loam (fine mixed Aeric Ochraqudalf ) near South Charleston, Ohio. The experimental design included two soils: undisturbed and desurfaced soil in which the top 0-cm to 20-cm layer was mechanically removed to simulate severe soil erosion. There were three cover treatments: bare soil, wheat mulch at the rate of 8 Mg dry matter ha-1 y-1, and compost made from swine manure and soybean residues at the rate of 20 Mg dry matter ha-1 y-1. All plots received mineral fertilizer at the rate of 100 kg N ha-1. Desurfacing decreased soil moisture, increased temperature, decreased daily and annual CO2 fluxes (1.05 vs. 1.59 g CO2-C m-2 d-1), and increased N2O fluxes (3.58 vs. 1.81 mg N2O-N m-2 d-1). Daily CO2 and annual fluxes were higher from compost than mulch plots. The lowest daily CO2 flux was measured from bare plots. The daily N2O fluxes significantly increased after compost application but were more significantly affected by rainfall events. CH4 fluxes were characterized by a high variability; however, more uptake was observed in compost (-0.41 kg ha-1 y-1) than in mulch (0.60 kg ha-1 y-1) and bare plots (2.75 kg ha-1 y-1). Daily CO2 fluxes were positively correlated with soil (r = 0.82) and air temperatures (r = 0.84) and negatively correlated with soil-moisture content (r = -0.53). Daily N2O fluxes were highly correlated with precipitation (r = 0.88). Fluxes of CO2 and N2O were mutually correlated (r = 0.56), but CH4 fluxes were not correlated with temperature, moisture, precipitation, or fluxes of other GHG. Computed GWP was higher in compost-covered plots than in mulched and bare plots. Estimation of fluxes of GHG indicates that N2O accounts for 13% to 28% and CH4 for -0.5% to 5% of the total emission. Therefore, a completed assessment of flux of GHG must be based on measurement of all three gases (i.e., CO2, N2O, and CH4).