• Authors:
    • Bosque-Pérez, N. A.
    • Eigenbrode, S. D.
    • Hatten, T. D.
    • Johnson-Maynard, J. L.
    • Umiker, K. J.
  • Source: Soil & Tillage Research
  • Volume: 105
  • Issue: 2
  • Year: 2009
  • Summary: Farmers within the Inland Pacific Northwest are gradually transitioning to direct seed (DS) practices that reduce soil disturbance and increase surface residue compared to conventional tillage (CT). Despite this transition the impacts of DS practices on soil properties and fauna in commercial fields has been little studied in the region. During the spring and summer of 2002 and 2003 we compared soil organic carbon (SOC), total nitrogen (TN), pH, and earthworm and cocoon densities in CT and DS fields planted to either spring wheat or pea in the Palouse region of northern Idaho. In 2002 mean SOC within the 0-10-cm depth was greater in DS fields (2.05%) than at the same depth in CT fields (1.79%), however SOC within the 30-40-cm depth was lower under DS compared to CT. Mean soil pH within the 0-10-cm depth was 5.35 under DS and 5.61 under CT indicating that pH stratification can occur when tillage is reduced. Tillage effects on SOC, TN, and pH were not found in 2003. Tillage also did not significantly influence earthworm densities, which averaged 39 individuals m-2 in 2002 and 57 individuals m-2 in 2003. Correlations were detected in 2003 DS fields between soil properties (SOC and TN) and earthworm and cocoon densities at depths above 30 cm while in 2002 correlations in DS fields occurred with cocoon density, but not with earthworm density. Direct seed management can increase near-surface SOC and TN concentrations compared to CT practices, however, SOC concentrations deeper in the soil appear to remain the same or possibly decrease. Higher SOC and TN near the soil surface, as found in DS fields, appear to promote greater earthworm densities, which may improve long-term soil productivity.
  • Authors:
    • Worth, D.
    • Desjardins, R. L.
    • Dyer, J. A.
    • Vergé, X. P. C.
  • Source: Livestock Science
  • Volume: 121
  • Issue: 1
  • Year: 2009
  • Summary: In order to determine the potential of production practices for reducing greenhouse gas (GHG)emissions, it is important to quantify the GHG emissions associated with various types of production. The methodology from the Intergovernmental Panel on Climate Change (IPCC) adjusted for conditions in Canada was used to calculate the GHG emissions from the Canadian pork industry for census years from 1981 to 2001. Emissions of CH4, N2O and CO2 from animals, their facilities and the crops used to feed them were estimated. The Pork Crop Complex (PCC), defined as the area used to grow the crops that feed all Canadian swine, was estimated using the recommended livestock feed rations. Fertilizer application and the use of fossil fuel were down-scaled from the national crop areas to the PCC. This study also estimated the GHG emission intensity based on the total weight of live animal production (destined for either slaughter or export). The growth of the swine population led to an increase in GHG emissions from the pork industry by 54% between 1981 and 2001. The main GHG was CH4, representing about 40% of the 6.7 TgCO2equiv. total in 2001. Nitrous oxide and fossil CO2 both accounted for about 30%. Due to changes in management practices, the GHG emission intensity of the Canadian swine industry decreased from 2.99 to 2.31 kg of CO2equiv. per kg of live market animal during the same period.
  • Authors:
    • Worth, D.
    • Desjardins, R. L.
    • Dyer, J. A.
    • Vergé, X. P. C.
  • Source: The Journal of Applied Poultry Research
  • Volume: 18
  • Issue: 2
  • Year: 2009
  • Summary: As people become more aware of the environmental footprint of different foods, consumers may modify their diets to reduce the impact of their diets on the environment. For this to occur, it is necessary to know the impact that individual food types have on the environment. This publication presents the greenhouse gas (GHG) emissions as well as the GHG emission intensity associated with various types of poultry production in Canada for the census years 1981 to 2006. Greenhouse gas emissions were calculated using the methodology from the Intergovernmental Panel on Climate Change adjusted for conditions in Canada. Direct emissions of CH4, N2O, and CO2 from birds, their facilities, and the avian crop complex, corresponding to the area used to grow the crops that feed Canadian poultry, were estimated using poultry diet surveys. Between 1981 and 2006, because of the strong growth of broiler production, GHG emissions from the poultry industry increased by 40%. The main GHG was N2O, representing approximately 57% of the total emissions. Fossil fuel CO2 accounted for approximately 38%, whereas CH4 accounted for 5%. In western Canada, GHG emission intensities decreased owing to a reduction in the consumption of fossil fuels associated with the adoption of reduced- and no-tillage cropping systems, whereas in eastern Canada, the reduction was due to lower N2O emissions. The emissions of all 3 GHG from turkeys decreased because of the more rapid turnover of a marketable product (shortened life span) in later census years. Compared with other Canadian meat protein commodities in 2001, poultry emitted only 47% as much GHG per unit of live weight as pork and only 10% as much GHG per unit of live weight as beef.
  • Authors:
    • Institute for the Study of Earth, Oceans and Space
  • Year: 2009
  • Summary: The DNDC model is a process-base model of carbon (C) and nitrogen (N) biogeochemistry in agricultural ecosystems. This document describes how to use the PC Windows versions of the DNDC model for predicting crop yield, C sequestration, nitrate leaching loss, and emissions of C and N gases in agroecosystems. Part I provides a brief description of the model structure with relevant scientific basis. Part II describes how to install the model. Part III and IV demonstrate how to conduct simulations with the site and regional versions of DNDC, respectively. Part V provides basic information for uncertainty analysis with DNDC. Part VI contains six case studies demonstrating the input procedures for simulating crop yield, soil C dynamics, nitrate leaching loss, and trace gas emissions. A list of relevant publications is included in Part VII. These publications provide more information about the scientific background and applications of DNDC far beyond this User's Guide. DNDC9.3 can run in two modes: site or regional. By selecting the mode, the users will open a corresponding interface to manage their input information for the modeled site or region.
  • Authors:
    • Jones, R.
    • Hatfield, J. L.
    • Kerr, B. J.
    • Singer, J. W.
    • Moorman, T. B.
    • Kaspar, T. C.
    • Chan, A. S. K.
    • Parkin, T. B.
    • Jarecki, M. K.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 134
  • Issue: 1-2
  • Year: 2009
  • Summary: Agriculture contributes 40-60% of the total annual N2O emissions to the atmosphere. Development of management practices to reduce these emissions would have a significant impact on greenhouse gas levels. Non-leguminous cover crops are efficient scavengers of residual soil NO3, thereby reducing leaching losses. However, the effect of a grass cover crop on N2O emissions from soil receiving liquid swine manure has not been evaluated. This study investigated: (i) the temporal patterns of N2O emissions following addition of swine manure slurry in a laboratory setting under fluctuating soil moisture regimes; (ii) assessed the potential of a rye (Secale cereale L.) cover crop to decrease N2O emissions under these conditions: and (iii) quantified field N2O emissions in response to either spring applied urea ammonium nitrate (UAN) or different rates of fall-applied liquid swine manure, in the presence or absence of a rye/oat winter cover crop. Laboratory experiments investigating cover crop effects N2O emissions were performed in a controlled environment chamber programmed fora 14 h light period, 18 degrees C day temperature, and 15 degrees C night temperature. Treatments with or without a living rye cover crop were treated with either: (i) no manure: (ii) a phosphorus-based manure application rate (low manure): or (iii) a nitrogen-based manure application rate (high manure). We observed a significant reduction in N2O emissions in the presence of the rye cover crop. Field experiments were performed on a fine-loamy soil in Central Iowa from October 12, 2005 to October 2, 2006. We observed no significant effect of the cover crop on cumulative N2O emissions in the field. The primary factor influencing N2O emission was N application rate, regardless of form or timing. The response of N2O emission to N additions was non-linear, with progressively more N2O emitted with increasing N application. These results indicate that while cover crops have the potential to reduce N2O emissions, N application rate may be the overriding factor.
  • Authors:
    • Jia, L.
    • Raun, W. R.
    • Schroder, J.
    • Zhang, H.
    • Chen, X.
    • Li, R.
    • Cui, Z.
    • Zhang, F.
    • Miao, Y.
    • Li, F.
  • Source: Soil Science Society of America Journal
  • Volume: 73
  • Issue: 5
  • Year: 2009
  • Summary: Optical sensor-based N management strategies are promising approaches to improve N-use efficiency (NUE) and reduce environmental pollution risk. The objective of this study was to evaluate an active optical sensor-based in-season N management strategy for winter wheat (Triticum aestivum L.) in the North China Plain (NCP). Initially, 10 field experiments were conducted at four villages in NCP in the 2004/05, 2005/06, and 2006/07 growing seasons to evaluate the in-season N requirement prediction developed by Oklahoma State University. Then the N application rates, winter wheat grain yield, NUE, economic returns, residual N content after harvest and apparent N loss were compared among three different management systems on a total of 16 farmer fields in 2005/2006 and 14 farmer fields in 2006/2007. The systems included a sensor-based system, a soil test-based approach crediting soil residual mineral N (N-min) to different depth at different growth stages, and common farmer practices. Averaged across site-years, the sensor-based, soil N-min-based N management strategies, and farmer practices produced similar grain yields but used 67, 88, and 372 kg N ha(-1), respectively. Nitrogen-use efficiencies were 61.3, 51.0, and 13.1% for the three methods of N recommendations, correspondingly. Their residual N content in the soil and apparent N loss were 115, 122, and 208 kg N ha(-1), and 4, 15, and 205 kg N ha(-1), respectively. The optical sensor-based N management strategy is relatively easy to use, has better potential to improve NUE and economic returns, and reduces residual soil N content and apparent N loss than other methods currently used in the NCP.
  • Authors:
    • Six, J.
    • Howitt, R. E.
    • Catalá-Luque, R.
    • Albarracin, M. V.
    • De Gryze, S.
  • Source: California Agriculture
  • Volume: 63
  • Issue: 2
  • Year: 2009
  • Summary: Agricultural management has a significant impact on the amount of greenhouse gases emitted by cropped fields. Alternative practices such as winter cover cropping and avoiding overfertilization can decrease the total amount of greenhouse gases that are produced. Policymakers are considering a structure in which parties (such as factories) who exceed their greenhouse-gas emissions cap can pay incentives to encourage farmers to adopt practices that curb greenhouse gases. Based on data from field studies and an ecosystem computer model, we assessed impacts on yields and the total potential for reducing greenhouse-gas emissions of certain alternative practices in California.
  • Authors:
    • Wong, C. P.
    • Neely, C. L.
    • Schohr, T.
    • Oldfield, J. T.
    • Laca, E. A.
    • Kustin, C.
    • George, M. R.
    • Brown, J. R.
    • Alvarez, P.
    • Fynn, A. J.
  • Year: 2009
  • Authors:
    • Jordan, D.
    • Owen, M. D. K.
    • Wilson, R. G.
    • Young, B. G.
    • Weller, S. C.
    • Johnson, W. G.
    • Kruger, G. R.
    • Shaw, D. R.
    • Givens, W. A.
  • Source: Weed Technology
  • Volume: 23
  • Issue: 1
  • Year: 2009
  • Summary: A phone survey was administered to 1,195 growers in six states (Illinois, Indiana, Iowa, Mississippi, Nebraska, and North Carolina). The survey measured producers' crop history, perception of glyphosate-resistant (GR) weeds, past and present weed pressure, tillage practices, and herbicide use as affected by the adoption of GR crops. This article describes the changes in tillage practice reported in the survey. The adoption of a GR cropping system resulted in a large increase in the percentage of growers using no-till and reduced-till systems. Tillage intensity declined more in continuous GR cotton and GR soybean (45 and 23%, respectively) than in rotations that included GR corn or non-GR crops. Tillage intensity declined more in the states of Mississippi and North Carolina than in the other states, with 33% of the growers in these states shifting to more conservative tillage practices after the adoption of a GR crop. This was primarily due to the lower amount of conservation tillage adoption in these states before GR crop availability. Adoption rates of no-till and reduced-till systems increased as farm size decreased. Overall, producers in a crop rotation that included a GR crop shifted from a relatively more tillage-intense system to reduced-till or no-till systems after implementing a GR crop into their production system.
  • Authors:
    • Euliss, N. H. Jr.
    • Browne, B. A.
    • Tangen, B. A.
    • Gleason, R. A.
  • Source: Soil Biology and Biochemistry
  • Volume: 41
  • Issue: 12
  • Year: 2009
  • Summary: It has been well documented that restored wetlands in the Prairie Pothole Region of North America do store carbon. However, the net benefit of carbon sequestration in wetlands in terms of a reduction in global warming forcing has often been questioned because of potentially greater emissions of greenhouse gases (GHGs) such as nitrous oxide (N2O) and methane (CH4). We compared gas emissions (N2O, CH4, carbon dioxide [CO2]) and soil moisture and temperature from eight cropland and eight restored grassland wetlands in the Prairie Pothole Region from May to October, 2003, to better understand the atmospheric carbon mitigation potential of restored wetlands. Results show that carbon dioxide contributed the most (90%) to net-GHG flux, followed by CH4 (9%) and N2O (1%). Fluxes of N2O, CH4, CO2, and their combined global warming potential (CO2 equivalents) did not significantly differ between cropland and grassland wetlands. The seasonal pattern in flux was similar in cropland and grassland wetlands with peak emissions of N2O and CH4 occurring when soil water-filled pore space (WFPS) was 40-60% and >60%, respectively; negative CH4 fluxes were observed when WFPS approached 40%. Negative CH4 fluxes from grassland wetlands occurred earlier in the season and were more pronounced than those from cropland sites because WFPS declined more rapidly in grassland wetlands; this decline was likely due to higher infiltration and evapotranspiration rates associated with grasslands. Our results suggest that restoring cropland wetlands does not result in greater emissions of N2O and CH4, and therefore would not offset potential soil carbon sequestration. These findings, however, are limited to a small sample of seasonal wetlands with relatively short hydroperiods. A more comprehensive assessment of the GHG mitigation potential of restored wetlands should include a diversity of wetland types and land-use practices and consider the impact of variable climatic cycles that affect wetland hydrology.