• Authors:
    • Hoffmann, M.
    • Donaghy, P.
    • Stunzer, A.
    • Bray, S.
    • Gowen, R.
    • Rolfe, J.
    • Stephens, M.
  • Source: Small-Scale Forestry
  • Volume: 9
  • Issue: 4
  • Year: 2010
  • Authors:
    • Fernandez, P. L.
    • Álvarez, C. R.
    • Schindler, V.
    • Taboada, M. A.
  • Source: Geoderma
  • Volume: 159
  • Issue: 1-2
  • Year: 2010
  • Summary: The grazing of crop residues during the winter in integrated crop-livestock systems can either increase soil bulk density (BD) by compaction or decrease BD by swelling, as a function of gravimetric soil water content (GW) during grazing. A field experiment was conducted from 2005 to 2008 to evaluate the BD response to grazing in a no-till silty loam soil (Typic Argiudoll) of the Pampas region of Argentina. Soil BD (core method), GW data and the calculated air volume (AV) were obtained from the 0-50 mm and 50-100 mm layers at different sampling times from ungrazed and grazed treatments. Over most of the study period (2006 through 2008) soil BD showed little impact from grazing, with minimal temporal variation (1.32-1.46 Mg m -3). This stable behavior was ascribed to low rainfall and relatively low GW values at the time when soil was trampled by livestock and routinely trafficked by machinery. Soil BD in the upper (0-50 mm) layer was significantly (p330 g kg -1 in the ungrazed treatment and GW was >240 g kg -1 in the grazed treatments. Grazing accentuated the soil kneading process that promoted air entrapment. Our results suggest in this no-tilled silt loam soil that winter grazing of crop residues caused no deterioration of topsoil porosity in the no-tilled silty loam soil.
  • Authors:
    • Waggoner, J. A.
    • Conover, D. M.
    • Kreuter, U. P.
    • Ansley, R. J.
    • Baker, S. A.
    • Dowhower, S. L.
    • Teague, W. R.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 137
  • Issue: 1
  • Year: 2010
  • Summary: This paper examines if post-fire deferment and periodic rests provided by rotational grazing allowed for more rapid recovery of soil cover, soil chemical and physical parameters, and vegetation composition after summer patch burning than continuous grazing. We evaluated the recovery of native rangeland vegetation and soils subjected to summer patch burns in continuously and rotationally grazed pastures in 2002, 2003 and 2004. Each year, 12% of each treatment replicate was burned as a single patch in a different, non-adjacent area under continuous grazing, and as a single paddock of a rotationally grazed 8-pasture-1-herd system. Recovery of vegetation and soils on burned patches were measured annually until the summer of 2006 and compared to those in immediately adjacent unburned areas in both grazing treatments. Herbaceous cover and biomass took 2 years to recover to control levels on soils with greater mesquite cover and more C-3 grasses, and 3 years on soils with more C-4 grasses. The rotational grazing treatment had less bare ground and lower soil temperatures on both unburned and burned areas than the continuously grazed treatment, which has significant implications for infiltration rates, runoff and erosion in favor of the rotational management. Soil C and C to N ratios were also higher with rotational grazing. Soil physical parameters were not affected by either the burn or grazing treatments but the presence of trees reduced soil temperature, improved soil physical parameters and infiltration rate relative to open grassland.
  • Authors:
    • Phillips, R. L.
    • Kronberg, S. L.
    • Gross, J. R.
    • Liebig, M. A.
  • Source: Journal of Environmental Quality
  • Volume: 39
  • Issue: 3
  • Year: 2010
  • Summary: The role of grassland ecosystems as net sinks or sources of greenhouse gases (GHGs) is limited by a paucity of information regarding management impacts on the flux of nitrous oxide (N2O) and methane (CH4). Furthermore, no long-term evaluation of net global warming potential (GWP) for grassland ecosystems in the northern Great Plains (NGP) of North America has been reported. Given this need, we sought to determine net GWP for three grazing management systems located within the NGP. Grazing management systems included two native vegetation pastures (moderately grazed pasture [MGP], heavily grazed pasture [HGP]) and a heavily grazed crested wheatgrass [Agropyron desertorum (Fisch. ex. Link) Schult.] pasture (CWP) near Mandan, ND. Factors evaluated for their contribution to GWP included (i) CO2 emissions associated with N fertilizer production and application, (ii) literature-derived estimates of CH4 production for enteric fermentation, (iii) change in soil organic carbon (SOC) over 44 yr using archived soil samples, and (iv) soil-atmosphere N2O and CH4 fluxes over 3 yr using static chamber methodology. Analysis of SOC indicated all pastures to be significant sinks for SOC, with sequestration rates ranging from 0.39 to 0.46 Mg C ha-1 yr-1. All pastures were minor sinks for CH4 (<2.0 kg CH4-C ha-1 yr-1). Greater N inputs within CWP contributed to annual N2O emission nearly threefold greater than HGP and MGP. Due to differences in stocking rate, CH4 production from enteric fermentation was nearly threefold less in MGP than CWP and HGP. When factors contributing to net GWP were summed, HGP and MGP were found to serve as net CO2equiv. sinks, while CWP was a net CO2equiv. source. Values for GWP and GHG intensity, however, indicated net reductions in GHG emissions can be most effectively achieved through moderate stocking rates on native vegetation in the NGP.
  • Authors:
    • Saggar, S.
    • de Klein, C. A. M.
    • Ledgard, S. F.
    • Luo, J.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 136
  • Issue: 3-4
  • Year: 2010
  • Summary: Nitrous oxide (N2O) emissions from grazed pastures represent a significant source of atmospheric N2O. With an improved understanding and quantification of N sources, transformation processes, and soil and climatic conditions controlling N2O emissions, a number of management options can be identified to reduce N2O emissions from grazed pasture systems. The mitigation options discussed in this paper are: optimum soil management, limiting the amount of N fertiliser or effluent applied when soil is wet; lowering the amount of N excreted in animal urine by using low-N feed supplements as an alternative to fertiliser N-boosted grass; plant and animal selection for increased N use efficiency, using N process inhibitors that inhibit the conversion of urea to ammonium and ammonium to nitrate in soil; use of stand-off/feed pads or housing systems during high risk periods of N loss. The use of single or multiple mitigation options always needs to be evaluated in a whole farm system context and account for total greenhouse gas emissions including methane and carbon dioxide. They should focus on ensuring overall efficiency gains through decreasing N losses per unit of animal production and achieving a tighter N cycle. Whole-system life-cycle-based environmental analysis should also be conducted to assess overall environmental emissions associated the N2O mitigation options. (C) 2009 Elsevier B.V. All rights reserved.
  • Authors:
    • Del Grosso, S. J.
  • Source: Nature
  • Volume: 464
  • Issue: 7290
  • Year: 2010
  • Summary: Most emissions of nitrous oxide from semi-arid, temperate grasslands usually occur during the spring thaw. The effects that grazing has on plant litter and snow cover dramatically reduce these seasonal emissions.
  • Authors:
    • Janssen, L. L.
    • Diersen, M. A.
    • Beutler, M. K.
    • Johnson, P. S.
    • Gates, R. N.
    • Smart, A. J.
    • Dunn, B. H.
  • Source: Rangeland Ecology & Management
  • Volume: 63
  • Issue: 20
  • Year: 2010
  • Summary: Conventional wisdom among rangeland professionals has been that for long-term sustainability of grazing livestock operations, rangeland should be kept in high good to low excellent range condition. Our objective was to analyze production parameters, costs, returns, and profit using data generated over a 34 year period (1969-2002) from grazing a Clayey range site in the mixed-grass prairie of western South Dakota with variable stocking rates to maintain pastures in low-fair, good, and excellent range condition classes. Cattle weights were measured at turnout and at the end of the grazing season. Gross income*ha-1 was the product of gain*ha-1 and price. Prices were based on historical National Agricultural Statistics Services feeder cattle prices. Annual variable costs were estimated using a yearling cattle budget developed by South Dakota State University agricultural economists. All economic values were adjusted to a constant dollar using the Bureau of Labor Statistics' Consumer Price Index. Stocking rate, average daily gain, total gain, net profit, gross revenue, and annual costs*ha-1 varied among range condition classes. Net income for low-fair range condition ($27.61*ha -1) and good range condition ($29.43*ha-1) were not different, but both were greater than excellent range condition ($23.01*ha-1). Over the life of the study, real profit (adjusted for inflation) steadily increased for the low-fair and good treatments while it remained level for the excellent treatment. Neither drought nor wet springs impacted profit differently for the three treatments. These results support generally observed rancher behavior regarding range condition: to maintain their rangeland in lower range condition than would be recommended by rangeland professionals. Ecosystem goods and services of increasing interest to society and associated with high range condition, such as floristic diversity, hydrologic function, and some species of wildlife, come at an opportunity cost to the rancher.
  • Authors:
    • Reed, D. A.
    • Follett, R. F.
  • Source: Rangeland & Ecology Management
  • Volume: 63
  • Issue: 1
  • Year: 2010
  • Summary: This forum manuscript examines the importance of grazing lands for sequestering soil organic carbon (SOC), providing societal benefits, and potential influences on them of emerging policies and legislation. Global estimates are that grazing lands occupy similar to 3.6 billion ha and account for about one-fourth of potential carbon (C) sequestration in world soils. They remove the equivalent of similar to 20% of the carbon dioxide (CO2) released annually into the earth's atmosphere from global deforestation and land-use changes. Atmospheric CO2 enters grazing lands soils through photosynthetic assimilation by green plants, subsequent cycling, and sequestration of some of that C as SOC to in turn contribute to the ability of grazing lands to provide societal (environmental and economic) benefits in every country where they exist. Environmental benefits provided include maintenance and well-being of immediate and surrounding soil and water resources, air quality, human and wildlife habitat, and esthetics. Grazing lands contribute to the economic well-being of those living on the land, to trade, and to exchange of goods and services derived from them at local, regional, or national levels. Rates of SOC sequestration vary with climate, soil, and management; examples and conditions selected from US literature illustrate the SOC sequestration that might be achieved. Public efforts, policy considerations, and research in the United States illustrate possible alternatives that impact grazing lands. Discussion of US policy issues related to SOC sequestration and global climate change reflect the importance attached to these topics and of pending legislative initiatives in the United States. Addressing primarily US policy does not lessen the importance of such issues in other countries, but allows an in-depth analysis of legislation, US Department of Agriculture program efforts, soil C credits in greenhouse gas markets, and research needs.
  • Authors:
    • Scholefield, D.
    • Dhanoa, M. S.
    • Lane, S.
    • Kingston, H.
    • Donovan, N.
    • Cuttle, S.
    • Chambers, B.
    • Chadwick, D.
    • Butler, M.
    • Ashleee, N.
    • Thorman, R.
    • Cardenas, L. M.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 136
  • Issue: 3-4
  • Year: 2010
  • Summary: The objective of the present study was to measure emissions of N2O from fertilized grazed grassland that can be used to add valuable information to the limited existing data on N2O fluxes from grazed grassland and aid the development of new country-specific EFs for direct emissions from soils in the UK. This was done by evaluating the effect on N2O emissions of inorganic fertiliser N applied to grazed grassland soils over the range of N inputs 0-350 kg ha(-1). Nitrous oxide fluxes were measured using closed static chambers at 3 sites in England and Wales over a two-year period. Cumulative fluxes were calculated and the total emission regressed against applied inorganic fertiliser N in order to estimate the emission factor for N2O emissions from soils. The data showed that, the emission factor for N2O from inorganic fertiliser applied to grazed grassland soils in the UK differs from the IPCC default value of 1.25%. A nonlinear response of N2O emissions to fertiliser N application rates was observed. Annual emissions of N2O were estimated from a modelled function fitted to the measured data and after subtraction of the background flux resulted in emissions of 0.5 and 3.9 kg N2O-N ha(-1) yr(-1) for an application of 100 kg N for three locations in the UK, one in the East and the other two in the West of the UK (after combining the data from two sites), respectively. (C) 2009 Elsevier B.V. All rights reserved.
  • Authors:
    • Sherlock, R. R.
    • Wells, N. S.
    • O'Callaghan, M.
    • Condron, L. M.
    • Ray, J. L.
    • Bertram, J. E.
    • Clough, T. J.
  • Source: Soil Science Society of America Journal
  • Volume: 74
  • Issue: 3
  • Year: 2010
  • Summary: Low-temperature pyrolysis of biomass produces a product known as biochar. The incorporation of this material into the soil has been advocated as a C sequestration method. Biochar also has the potential to influence the soil N cycle by altering nitrification rates and by adsorbing NH or NH3. Biochar can be incorporated into the soil during renovation of intensively managed pasture soils. These managed pastures are a significant source of N2O, a greenhouse gas, produced in ruminant urine patches. We hypothesized that biochar effects on the N cycle could reduce the soil inorganic-N pool available for N2O-producing mechanisms. A laboratory study was performed to examine the effect of biochar incorporation into soil (20 Mg ha-1) on N2O-N and NH3-N fluxes, and inorganic-N transformations, following the application of bovine urine (760 kg N ha-1). Treatments included controls (soil only and soil plus biochar), and two urine treatments (soil plus urine and soil plus biochar plus urine). Fluxes of N2O from the biochar plus urine treatment were generally higher than from urine alone during the first 30 d, but after 50 d there was no significant difference (P = 0.11) in terms of cumulative N2O-N emitted as a percentage of the urine N applied during the 53-d period; however, NH3-N fluxes were enhanced by approximately 3% of the N applied in the biochar plus urine treatment compared with the urine-only treatment after 17 d. Soil inorganic-N pools differed between treatments, with higher NH concentrations in the presence of biochar, indicative of lower rates of nitrification. The inorganic-N pool available for N2O-producing mechanisms was not reduced, however, by adding biochar.