• Authors:
    • Schilizzi, S.
    • Flugge, F.
  • Source: Ecological Economics
  • Volume: 55
  • Issue: 4
  • Year: 2005
  • Authors:
    • Paustian,Keith
    • Cole,C. Vernon
    • Sauerbeck,Dieter
    • Sampson,Neil
    • Peairs,F. B.
    • Bean,B.
    • Gossen,B. D.
  • Source: Agronomy Journal
  • Volume: 97
  • Issue: 2
  • Year: 2005
  • Summary: The intensification of traditional wheat (Triticum aestivum L.)-fallow production systems may have important consequences for management of insects, pathogens, and weeds in Great Plains dryland production systems. Assessment of these consequences is difficult due to the diversity of production systems, environmental conditions, and pests found in the region. Certain pest groups, such as weeds, traditionally controlled during the fallow period, may be favored by intensified cropping while others, such as those specializing on wheat, should be disadvantaged. Changes in pest and disease complexes will likely be evolutionary rather than revolutionary, as has been the case with other significant changes in production practices. Preventive practices in dryland production systems currently emphasize the control of grassy weeds while intensified systems may have less emphasis on the control of volunteer wheat. Crop rotation will remain a key avoidance strategy for pathogens and will help broaden herbicide options. Pest monitoring provides essential information on pest activity and environmental conditions and will become more complex as production systems are intensified. Important suppressive practices for dryland production systems include conservation biological control, tillage, and chemical controls. Chemical control, in particular, is expected to become more complicated due to drift concerns, rotational restrictions, the possible need for herbicide-tolerant crops, and the development of weed populations resistant to glyphosate. Pest management requirements should be considered during cropping system design and establishment.
  • Authors:
    • Traxler, G.
    • Qaim, M.
  • Source: Agricultural Economics
  • Volume: 32
  • Issue: 1
  • Year: 2005
  • Authors:
    • O'Neil, K.
    • Nyiraneza ,J.
    • Leep, R.
    • Black, J. R.
    • Mutch, D.
    • Labarta, R.
    • Swinton, S. M.
    • Snapp, S. S.
  • Source: Agronomy Journal
  • Volume: 97
  • Issue: 1
  • Year: 2005
  • Summary: The integration of cover crops into cropping systems brings costs and benefits, both internal and external to the farm. Benefits include promoting pest-suppression, soil and water quality, nutrient cycling efficiency, and cash crop productivity. Costs of adopting cover crops include increased direct costs, potentially reduced income if cover crops interfere with other attractive crops, slow soil warming, difficulties in predicting N mineralization, and production expenses. Cover crop benefits tend to be higher in irrigated systems. The literature is reviewed here along with Michigan farmer experience to evaluate promising cover crop species for four niches.
  • Authors:
    • Dell, C. J.
    • Venterea, R. T.
    • Sauer, T. J.
    • Allmaras, R. R.
    • Reicosky, D. C.
    • Johnson, J. M. F
  • Source: Soil & Tillage Research
  • Volume: 83
  • Issue: 1
  • Year: 2005
  • Summary: The central USA contains some of the most productive agricultural land of the world. Due to the high proportion of land area committed to crops and pasture in this region, the carbon (C) stored and greenhouse gas (GHG) emission due to agriculture represent a large percentage of the total for the USA. Our objective was to summarize potential soil organic C (SOC) sequestration and GHG emission from this region and identify how tillage and cropping system interact to modify these processes. Conservation tillage (CST), including no-tillage (NT), has become more widespread in the region abating erosion and loss of organic rich topsoil and sequestering SOC. The rate of SOC storage in NT compared to conventional tillage (CT) has been significant, but variable, averaging 0.40 ± 0.61 Mg C ha-1 year-1 (44 treatment pairs). Conversion of previous cropland to grass with the conservation reserve program increased SOC sequestration by 0.56 ± 0.60 Mg C ha-1 year-1 (five treatment pairs). The relatively few data on GHG emission from cropland and managed grazing land in the central USA suggests a need for more research to better understand the interactions of tillage, cropping system and fertilization on SOC sequestration and GHG emission.
  • Authors:
    • Johnson, D. W.
    • Moeltner, K.
    • van Kooten, G. C.
    • Manley, J.
  • Source: Climatic Change
  • Volume: 68
  • Issue: 1-2
  • Year: 2005
  • Summary: Carbon terrestrial sinks are often seen as a low-cost alternative to fuel switching and reduced fossil fuel use for lowering atmospheric CO2. To determine whether this is true for agriculture, one meta-regression analysis (52 studies, 536 observations) examines the costs of switching from conventional tillage to no-till, while another (51 studies, 374 observations) compares carbon accumulation under the two practices. Costs per ton of carbon uptake are determined by combining the two results. The viability of agricultural carbon sinks is found to vary by region and crop, with no-till representing a low-cost option in some regions (costs of less than $10 per tC), but a high-cost option in others (costs of $100-$400 per tC). A particularly important finding is that no-till cultivation may store no carbon at all if measurements are taken at sufficient depth. In some circumstances no-till cultivation may yield a triple dividend of carbon storage, increased returns and reduced soil erosion, but in many others creating carbon offset credits in agricultural soils is not cost effective because reduced tillage practices store little or no carbon.
  • Authors:
    • Johnsen, T. N.
    • McLain, J. E. T.
    • Emmerich, W.
    • Martens, D. A.
  • Source: Soil & Tillage Research
  • Volume: 83
  • Issue: 1
  • Year: 2005
  • Summary: Agriculture in the southwestern USA is limited by water supply due to high evaporation and limited seasonal precipitation. Where water is available, irrigation allows for production of a variety of agricultural and horticultural crops. This review assesses the impacts of agriculture on greenhouse gas emission and sequestration of atmospheric C in soils of the hot, dry region of the southwestern USA. In Texas, conservation tillage increased soil organic C by 0.28 Mg C ha(-1) year(-1) compared with more intensive tillage. Conversion of tilled row crops to the conservation reserve program or permanent pastures increased soil organic C by 0.32 +/- 0.50 Mg C ha(-1) year(-1). Soil organic C sequestration was dependent on rotation, previous cropping, and type of conservation tillage employed. Relatively few studies have interfaced management and C cycling to investigate the impacts of grazing management on soil organic C, and therefore, no estimate of C balance was available. Irrigated crop and pasture land in Idaho had soil organic C content 10-40 Mg C ha(-1) greater than in dryland, native grassland. Soil salinity must be controlled in cropland as soil organic C content was lower with increasing salinity. Despite 75% of the region's soils being classified as calcic, the potential for sequestration of C as soil carbonate has been only scantly investigated. The region may be a significant sink for atmospheric methane, although in general, trace gas flux from semiarid soils lacks adequate characterization. Agricultural impacts on C cycling will have to be better understood in order for effective C sequestration strategies to emerge. Published by Elsevier B.V.
  • Authors:
    • Milbrandt, A.
  • Source: Technical Report
  • Year: 2005
  • Authors:
    • Culpepper, A. S.
    • Young, B. G.
    • Mitchell, P. D.
    • Mueller, T. C.
  • Source: Weed Technology
  • Volume: 19
  • Issue: 4
  • Year: 2005
  • Summary: The value of glyphosate has been compromised in some fields where weed populations have developed resistance or tolerant species increased. Three case studies related to reduced control from glyphosate are: (1) a weed population that has become resistant to glyphosate, with horseweed in Tennessee as an example; (2) a weed population increases due to lack of control in ‘‘glyphosate only’’ systems, with tropical spiderwort in Georgia cotton used as an example; and (3) the hypothetical resistance of common waterhemp to glyphosate in Illinois. For each of these case studies, an economic analysis was performed using a partial budget approach. This economic analysis provides the cost of control to the farmer when glyphosate fails to control these weeds and gives a critical time in years to compare different glyphosate resistance management philosophies (applicable only before resistance has evolved). The cost of glyphosate-resistant horseweed in cotton-soybeancorn rotation in Western Tennessee was calculated to be $30.46/ha per year. The cost of tropical spiderwort in cotton in southern Georgia was calculated to be $35.07/ha per year. The projected cost if common waterhemp were to develop glyphosate resistance in a corn-soybean rotation in southern Illinois was projected to be $44.25/ha per year, and the critical time was determined to be greater than 20 yr, indicating that a resistance management strategy would extend the value of glyphosateresistant crops.
  • Authors:
    • Massheder, J.
    • Smith, P.
    • Wright, J.
    • Smith, K. A.
    • Smith, J.
    • Flynn, H. C.
  • Source: Global Change Biology
  • Volume: 11
  • Issue: 9
  • Year: 2005
  • Summary: The current Intergovernmental Panel on Climate Change (IPCC) default methodology (tier 1) for calculating nitrous oxide (N2O) emissions from nitrogen applied to agricultural soils takes no account of either crop type or climatic conditions. As a result, the methodology omits factors that are crucial in determining current emissions, and has no mechanism to assess the potential impact of future climate and land-use change. Scotland is used as a case study to illustrate the development of a new methodology, which retains the simple structure of the IPCC tier 1 methodology, but incorporates crop- and climate-dependent emission factors (EFs). It also includes a factor to account for the effect of soil compaction because of trampling by grazing animals. These factors are based on recent field studies in Scotland and elsewhere in the UK. Under current conditions, the new methodology produces significantly higher estimates of annual N2O emissions than the IPCC default methodology, almost entirely because of the increased contribution of grazed pasture. Total emissions from applied fertilizer and N deposited by grazing animals are estimated at 10 662 tN2O-Nyr-1 using the newly derived EFs, as opposed to 6 796 tN2O-Nyr-1 using the IPCC default EFs. On a spatial basis, emission levels are closer to those calculated using field observations and detailed soil modelling than to estimates made using the IPCC default methodology. This can be illustrated by parts of the western Ayrshire basin, which have previously been calculated to emit 8-9 kgN2O-Nha-1yr-1 and are estimated here as 6.25-8.75 kgN2O-Nha-1yr-1, while the IPCC default methodology gives a maximum emission level of only 3.75 kgN2O-Nha-1 yr-1 for the whole area. The new methodology is also applied in conjunction with scenarios for future climate- and land-use patterns, to assess how these emissions may change in the future. The results suggest that by 2080, Scottish N2O emissions may increase by up to 14%, depending on the climate scenario, if fertilizer and land management practices remain unchanged. Reductions in agricultural land use, however, have the potential to mitigate these increases and, depending on the replacement land use, may even reduce emissions to below current levels.