• Authors:
    • Hedderley, D. I.
    • Barlow, H. E.
    • Francis, G. S.
    • Beare, M. H.
    • Thomas, S. M.
  • Source: Plant and Soil
  • Volume: 309
  • Issue: 1
  • Year: 2008
  • Summary: Nitrous oxide (N2O) emissions to the atmosphere from grazed pasture can be high, especially from urine-affected areas. When pastoral soils are damaged by animal treading, N2O emissions may increase. In New Zealand, autumn-sown winter forage crops are often grown as a break-crop prior to re-sowing pasture. When these crops are grazed in situ over winter (as is common in New Zealand) there is high risk of soil damage from animal treading as soil moisture contents are often high at this time of year. Moreover, the risk of soil damage during grazing increases when intensive tillage practices are used to establish these forage crops. Consequently, winter grazed forage crops may be an important source of N2O emissions from intensive pastoral farming systems, and these emissions may be affected by the type of tillage used to establish them. We conducted a replicated field experiment to measure the effects of simulated cattle grazing (mowing followed by simulated treading and the application of synthetic urine) at three soil moisture contents ( field capacity) on measured N2O emissions from soil under an autumn (March) sown winter forage crop (triticale) established with three levels of tillage intensity: (a) intensive, IT, (b) minimum, MT, or (c) no tillage, NT. In all treatments, bulk density in the top 7.5 cm of the soil was unaffected by treading when simulated grazing occurred at field capacity, and by 10% in the MT plots trodden at > field capacity. Treading did not significantly increase the bulk density in the NT plots. Emissions of N2O from the tillage treatments decreased in the order IT > MT > NT. N2O emissions were greatest from plots that were trodden at > field capacity and least from plots trodden at field capacity. The N2O emission from urine-amended NT plots that were trodden at < field capacity was 2.0 kg ha(-1) over 90 days (0.25% of the total urine N applied). Decreasing the intensity of tillage used to establish crops and restricting grazing when soils are wet are two of the most effective ways to minimise the risk of high N2O emissions from grazed winter forage crops.
  • Authors:
    • de Steiguer, J. E.
  • Source: Rangelands
  • Volume: 30
  • Issue: 2
  • Year: 2008
  • Authors:
    • Waggoner, J. W.,Jr.
    • Smith, M. A.
    • Hart ,R. H.
    • Derner, J. D.
  • Source: Livestock Science
  • Volume: 117
  • Issue: 1
  • Year: 2008
  • Summary: The effects of stocking rate and grazing system on gains of yearling beef cattle grazing rangelands have largely been addressed in short-term (<10 years) studies, and often stocking rates are confounded within grazing systems with higher stocking rates for short-duration rotational grazing systems compared to season-long grazing. A grazing system (season-long and short-duration rotational grazing) x stocking rate (light: 16 steers/80 ha, 18.0 animal unit days/ha; moderate: 4 steers/12 ha, 30.1 animal unit days/ ha, and heavy: 4 steers/9 ha, 40.1 animal unit days/ha) study was initiated in 1982 on northern mixed-grass prairie. Here, we report on the final 16 years (1991-2006) for yearling beef cattle gains, Average daily gains (kg/head/day) across all years with season-long grazing decreased with increasing stocking rate and grazing pressure. Heavy stocking rates reduced average daily gain by 16% and 12% compared to light and moderate stocking rates, respectively. In contrast to average daily gain, beef production (kg/ha) increased with increasing stocking rate and grazing pressure. Cattle gains were reduced by 6% with short-duration rotation compared to season-long grazing over the study period, with differences between systems observed in years with average, but not dry or wet, spring (April+May+June) precipitation. Grazing season gains (kg/head) and beef production both exhibited significant increasing hyperbolic relationships with spring precipitation, with the percentage of variation explained by spring precipitation substantially higher (62-83%) for beef production compared to grazing season gains (32-45%). The influence of spring precipitation on cattle gains suggests that incorporation of these relationships into modeling efforts for strategic planning and risk assessment will assist land managers in better matching forage and animal resources for greater sustainability in this highly variable environment.
  • Authors:
    • Paton, R. J.
    • Morton, J. D.
    • Littlejohn, R. P.
    • Houlbrooke, D. J.
  • Source: Soil Use and Management
  • Volume: 24
  • Issue: 4
  • Year: 2008
  • Summary: The North Otago Rolling Downlands (NORD) of New Zealand is currently undergoing a large change in land use with subsequent intensification as a result of a new large community irrigation scheme. To assess the effect of this change, a 4-year monitoring survey was established on two common Pallic soil types of the area to determine the influence of irrigation term (short, 5 years) and grazing animal (cattle vs. sheep) on a range of physical and organic matter soil quality parameters. This 4-year survey also included the historical land use of dryland sheep farming in the absence of irrigation water. Irrigation term had no significant (P > 0.05) effect on soil physical parameters (percentage macroporosity and bulk density) for 3 of 4 years and no significant effect (P > 0.05) on topsoil total carbon or nitrogen contents. However, irrigation term had a significant (P < 0.01) but biologically small effect on the ratio of carbon to nitrogen with narrowing of the range under longer term irrigation. A significant difference between the dryland and irrigated surveys was found for macroporosity (dryland sheep 17.3% v/v vs. irrigated sheep 13.4% v/v; P < 0.001) and for the C:N ratio (dryland sheep 10.7 vs. irrigated sheep 10.2; P < 0.05). The change in macroporosity under irrigation is likely to take effect within 1 or 2 years of land-use change as little discernable differences in soil physical properties were evident from land under short- or long-term irrigation.
  • Authors:
    • Derner, J. D.
    • Welker, J. M.
    • Ganjegunte, G. K.
    • Vance, G. F.
    • Buyer, J. S.
    • Schuman, G. E.
    • Stahl, P. D.
    • Ingram, L. J.
  • Source: Soil Science Society of America Journal
  • Volume: 72
  • Issue: 4
  • Year: 2008
  • Summary: Good management of rangelands promotes C sequestration and reduces the likelihood of these ecosystems becoming net sources of CO2. As part of an ongoing study, soil was sampled in 2003 to investigate the long-term effects of different livestock grazing treatments on soil organic carbon (SOC), total nitrogen (TN), and microbial communities. The three treatments studied (no grazing, EX; continuously, lightly grazed [10% utilization], CL; and continuously, heavily grazed [50% utilization], CH) have been imposed on a northern mixed-grass prairie near Cheyenne, WY, for 21 yr. In the 10 yr since treatments were last sampled in 1993, the study area has been subject to several years of drought. In the 0 to 60 cm depth there was little change in SOC in the EX or CL treatments between 1993 and 2003, whereas there was a 30% loss of SOC in the CH treatment. This loss is attributed to plant community changes (from a cool-season [C-3] to a warm-season [C-4] plant dominated community) resulting in organic C accumulating nearer the soil surface, making it more vulnerable to loss. Soil TN increased in the EX and CL treatments between 1993 and 2003, but declined in the CH treatment. Differences in plant community composition and subsequent changes in SOC and TN may have contributed to microbial biomass, respiration, and N-mineralization rates generally being greatest in CL and least in the CH treatment. Although no significant differences were observed in any specific microbial group based on concentrations of phospholipid fatty acid (PLFA) biomarkers, multivariate analysis of PLFA data revealed that microbial community structure differed among treatments. The CH grazing rate during a drought period altered plant community and microbial composition which subsequently impacted biogeochemical C and N cycles.
  • Authors:
    • Hutchins, B.
    • Groover, G.
    • Stephenson, K.
    • Bosch, D. J.
  • Source: Journal of Soil and Water Conservation
  • Volume: 63
  • Issue: 2
  • Year: 2008
  • Summary: Intensive rotational grazing systems may produce multiple environmental services, including reduction of the emissions of greenhouse gases (GHG). This study investigates potential GHG emission reduction credits obtained by converting Virginia cow-calf and dairy farm operations from conventional grazing operations to rotational grazing. The quantity and value of the change in GHG emissions are estimated using new US Department of Energy guidelines. Credits are estimated under three boundary conditions and two accounting metrics. Results suggest conversion to rotational grazing can generate GHG reduction credits, but the financial benefits farms receive from emissions reductions are modest. The amount of credits received is sensitive to choice of accounting metric and boundary definition.
  • Authors:
    • Willms, W. D.
    • Ash, A. J.
    • Gillen, R. L.
    • Havstad, K. M.
    • Teague, W. R.
    • Fublendor, S. D.
    • Brown, J. R.
    • Derner, J. D.
    • Briske, D. D.
  • Source: Rangeland Ecology & Management
  • Volume: 61
  • Issue: 1
  • Year: 2008
  • Summary: In spite of overwhelming experimental evidence to the contrary, rotational grazing continues to be promoted and implemented as the only viable grazing strategy. The goals of this synthesis are to 1) reevaluate the complexity, underlying assumptions, and ecological processes of grazed ecosystems, 2) summarize plant and animal production responses to rotational and continuous grazing, 3) characterize the prevailing perceptions influencing the assessment of rotational and continuous grazing, and 4) attempt to direct the profession toward a reconciliation of perceptions advocating support for rotational grazing systems with that of the experimental evidence. The ecological relationships of grazing systems have been reasonably well resolved, at the scales investigated, and a continuation of costly grazing experiments adhering to conventional research protocols will yield little additional information. Plant production was equal or greater in continuous compared to rotational grazing in 87% (20 of 23) of the experiments. Similarly, animal production per head and per area were equal or greater in continuous compared to rotational grazing in 92% (35 of 38) and 84% (27 of 32) of the experiments, respectively. These experimental data demonstrate that a set of potentially effective grazing strategies exist, none of which have unique properties that set one apart from the other in terms of ecological effectiveness. The performance of rangeland grazing strategies are similarly constrained by several ecological variables establishing that differences among them are dependent on the effectiveness of management models, rather than the occurrence of unique ecological phenomena. Continued advocacy for rotational grazing as a superior strategy of grazing on rangelands is founded on perception and anecdotal interpretations, rather than an objective assessment of the vast experimental evidence. We recommend that these evidence-based conclusions be explicitly incorporated into management and policy decisions addressing this predominant land use on rangelands.
  • Authors:
    • Leistritz, F. L.
    • Bangsund, D. A.
  • Source: Management of Environmental Quality: An International Journal
  • Volume: 19
  • Issue: 1
  • Year: 2008
  • Summary: Purpose - The purpose of this paper is to identify and describe key economic and policy-related issues with regard to terrestrial C sequestration and provide an overview of the economics of C sequestration on agricultural soils in the USA. Design/methodology/approach - Recent economic literature on carbon sequestration was reviewed to gather insights on the role of agriculture in greenhouse gas emissions mitigation. Results from the most salient studies were presented in an attempt to highlight the general consensus on producer-level responses to C sequestration incentives and the likely mechanisms used to facilitate C sequestration activities on agricultural soils. Findings - The likely economic potential of agriculture to store soil C appears to be considerably less than the technical potential. Terrestrial C sequestration is a readily implementable option for mitigating greenhouse gas emissions and can provide mitigation comparable in cost to current abatement options in other industries. Despite considerable research to date, many aspects of terrestrial C sequestration in the USA are not well understood. Originality/value - The paper provides a useful synopsis of the terms and issues associated with C sequestration, and serves as an informative reference on the economics of C sequestration that will be useful as the USA debates future greenhouse gas emissions mitigation policies.
  • Authors:
    • Roel, A.
    • Terra, J.
    • Pravia, M.
  • Source: Proceedings of the 9th International Conference on Precision Agriculture, Denver, Colorado, USA, 20-23 July, 2008
  • Year: 2008
  • Summary: Soil management practices impacts on sorghum ( Sorghum bicolor) productivity have rarely been evaluated at field-scale. Field-scale soil management practices effects on sorghum grain yield were evaluated in three no-till crop-pasture rotation systems during two years in Uruguay (Oxyaquic Argiudoll). Treatments were established in a randomized complete block design in strips traversing the landscape in a sorghum-soyabean ( Glycine max) sequence integrated in three rotation systems: (1) continuous cropping (CC) with a winter cover crop of Lolium multiflorum; (2) short rotation (SR): two years pasture of T. pratense and L. multiflorum and two years of CC and; (3) long rotation (LR) four years pasture of Dactylis glomerata, Trifolium repens and Lotus corniculatus and two years of CC. Strips treatments included a factorial arrangement of two levels of cover crop residues (generated by winter grazing) with and without paraplough subsoiling. Strips were harvested with a combine equipped with a yield monitor. Data were analysed with mixed models accounting for spatial correlation. Yield was affected by year and rotation system but was not affected by management practices; either residue or subsoiling. Although its lower soil quality, CC had greater yield than SR and LR in 2006 (8.61 vs. 8.1 and 7.75 tonnes ha -1, respectively); however, no differences existed in 2007 (4.58 tonnes ha -1). Yield variations between field topographic zones were only found in 2007 SR (35%). Weak evidence of spatial correlation was found for soil properties at the site. No correlations were found between soil chemical properties and yield. Accounting for spatial correlation of 2006-2007 yields improved the statistical analysis. Animal treading and grazing did not appear to affect yield. For undegraded soils in temperate climates, cropping systems including no-tillage and perennial pastures preserved soil C, but did not guaranteed the same levels of grain productivity than more intensive cropping systems.
  • Authors:
    • Babu, C.
    • Sureshkumar, P.
    • Sivakumar, S.
    • Chandaragiri, K.
    • Thirukumaran, K.
    • Ramesh, S.
    • Umashankar, R.
  • Source: Journal of Ecobiology
  • Volume: 19
  • Issue: 1
  • Year: 2007
  • Summary: Field experiments were carried out at the Tamil Nadu Agricultural University farm, Coimbatore, India, during north-east monsoon seasons of 2000-01 and 2001-02 to design a viable farming system by linking the crop and animal components viz., goat, rabbit and pigeon to sustain crop productivity and profitability and increasing the employment opportunity of dry land farmers. Among the different crops in the farming systems, pearl millet (cumbu) + soyabean grain, maize + cowpea fodder and Cenchrus ciliaris + Stylosanthes scabra fodder system with goat, rabbit and pigeon system were higher economic parameters in the second year than the first year. The economics of the integrated farming system revealed the superiority of pearl millet + soyabean grain, maize + cowpea fodder and C. ciliaris + S. scabra fodder with goat, rabbit and pigeon system in terms of higher total returns of Rs. 162 616 and 206 942, net returns of Rs. 80 924 and 125 250, benefit-cost ratio of 1.99 and 2.53 for every rupee invested and the per day returns (Rs.222 and 343) compared to other systems in first and second year, respectively. It also generated maximum employment opportunity of 490 man-days per year compared to other systems.