• Authors:
    • Silva, E. M. da
    • Rauber, J. C.
    • Azevedo, J. A. de
    • Reatto, A.
  • Source: Boletim de Pesquisa e Desenvolvimento - Embrapa Cerrados
  • Issue: 101
  • Year: 2003
  • Summary: The no-till system have positive impacts in soil and water conservation. This work aims to evaluate the main modifications on the soil physical properties caused by no-till system, carried out during 3, 6, and 12 years under rainfed conditions. The cases of direct drilling for five years under irrigated condition, a conventional tillage system, and a soil condition under natural Biome Cerrado were also evaluated in the Ampessan farm, Cabeceiras, Goias, Brazil. The soil physical characteristics were evaluated by samples taken from the following layers: 0-5, 2.5-7.5, 5-10, 10-15, 20-25, 42.5-47.5 and 72.5-77.5 cm. The infiltration characteristics were evaluated at 12 and 80 cm soil depth, using the Guelph permeameter to determine the field saturated hydraulic conductivity. The results showed that the intense soil mechanization on irrigated condition favoured a significant decrease in the field saturated hydraulic conductivity in the layers near to the soil surface. There was a tendency for higher water availability in the cultivated soils, in relation to that under natural soil environment, up to 22.5 cm soil depth.
  • Authors:
    • Nunes, R. P.
    • Pinho, J. L. N.
    • Silva, J. B. F.
    • Pitombeira, J. B.
    • Cavalcante Junior, A. T.
  • Source: Planta Daninha
  • Volume: 21
  • Issue: 1
  • Year: 2003
  • Summary: A study was conducted from September to December 1997, in Pentecoste, Ceara, Brazil, to determine the effectiveness of the herbicides glyphosate (1800 g ha -1) and paraquat (800 g ha -1), applied as desiccants before sowing, and fenoxaprop-P-ethyl [fenoxaprop-P] (0, 40, 80 and 120 g ha -1) and imazamox (0, 21, 42 and 63 g ha -1), applied in post-emergence conditions, in controlling the weeds and to evaluate the phytotoxicity of the herbicides to cowpea plants ( Vigna unguiculata cv. Epace 10) under a no-tillage system with furrow irrigation. The treatments with glyphosate associated with imazamox or fenoxaprop-P-ethyl was more efficient in controlling the weeds, showing reduced weed shoot dry biomass production, when compared to paraquat combined with the post-emergence herbicides. Fenoxaprop-P-ethyl and imazamox did not cause visual phytotoxicity symptoms to the cowpea plants. The best post-emergence weed control was provided by fenoxaprop-P-ethyl at the rate of 80 g ha -1, associated with glyphosate (1800 g ha 1). Fenoxaprop-P-ethyl was effective against the grass weeds, but not against Cenchrus echinatus and Digitaria horizontalis. Imazamox was not effective in controlling the broadleaf weeds Chamaesyce hirta and Euphorbia heterophylla at the studied rates.
  • Authors:
    • Turvey, C. G.
    • Kay, B. D.
    • Joseph, S.
    • Weersink, A.
  • Source: CAFRI: Current Agriculture, Food and Resource Issues
  • Volume: 4
  • Year: 2003
  • Summary: The objective of the 1997 Kyoto agreement was to limit greenhouse gas (GHG) emissions among signatory countries and thereby slow global warming. Under the agreement, Canada has committed itself to reduce GHGs over the next decade by 6 percent from estimated 1990 levels. Debate has now begun on the appropriate government policies that will induce the desired GHG reductions. Regulations could be in the form of direct controls or economic incentives, such as a subsidy/tax system or an emission trading system. The success of the U.S. emission market for SO2 (Schmalenseeet al., 1998) has generated growing interest in the use of a similar market mechanism for carbon (Holmes and Friedman, 2000). The existence of a carbon credit market presents the agricultural sector with another potential revenue source (Sandor and Skees, 1999). While agriculture contributes approximately 10 percent of Canada’s greenhouse gas emissions, it also has the potential to sequester carbon through strategies such as zero tillage, reduced summer fallow and improved grazing. These sequestration activities could be incorporated into an emission trading system and create a “carbon credit” for each unit of CO2 that is removed from the atmosphere. Firms with high emission reduction costs could then buy these credits rather than bear the large abatement costs associated with reducing their GHG emission levels. The perception is that the marginal cost of abatement for agriculture is less than that for other sectors (McCarl and Schneider, 2000). Thus, farmers may be able to profit by selling credits for activities that sequester carbon. An example of such a transaction was the purchase of carbon credits from Iowa farmers who adopted no-till by a consortium of Canadian energy companies (GEMCO) (Lessiter, 1999). Whether the development of a carbon credit market will affect the management decisions of an Ontario crop farmer is the focus of this study.
  • Authors:
    • Marland, G.
    • West, T. O.
  • Source: Biogeochemistry
  • Volume: 63
  • Issue: 1
  • Year: 2003
  • Summary: There is a potential to sequester carbon in soil by changing agricultural management practices. These changes in agricultural management can also result in changes in fossil-fuel use, agricultural inputs, and the carbon emissions associated with fossil fuels and other inputs. Management practices that alter crop yields and land productivity can affect the amount of land used for crop production with further significant implications for both emissions and sequestration potential. Data from a 20-year agricultural experiment were used to analyze carbon sequestration, carbon emissions, crop yield, and land-use change and to estimate the impact that carbon sequestration strategies might have on the net flux of carbon to the atmosphere. Results indicate that if changes in management result in decreased crop yields, the net carbon flux can be greater under the new system, assuming that crop demand remains the same and additional lands are brought into production. Conversely, if increasing crop yields lead to land abandonment, the overall carbon savings from changes in management will be greater than when soil carbon sequestration alone is considered.
  • Authors:
    • Chan, K. Y.
    • Heenan, D. P.
    • So, H. B.
  • Source: Australian Journal of Experimental Agriculture
  • Volume: 43
  • Issue: 4
  • Year: 2003
  • Authors:
    • Acosta-Martinez, V.
    • Gill, T. E.
    • Zobeck, T. M.
    • Kennedy, A. C.
  • Source: Biology and Fertility of Soils
  • Volume: 38
  • Issue: 4
  • Year: 2003
  • Summary: Microbes (i.e., fungi and bacteria) are needed to maintain the quality of semiarid soils and crop production. Enzyme (produced by microbes) activities were increased in the soil when cotton was rotated with sorghum or wheat under reduced or no-tillage in comparison to continuous cotton under tillage. Soil bacteria and fungi did not change, according to one analysis conducted, due to crop rotation under reduced or no-tillage in comparison to continuous cotton under tillage. The increases in enzyme activities, however, are indicating that microbes and their enzymes will be increased, and thus nutrients will be more available to plants, more organic matter will be formed, and other soil properties will also positively change if crop rotations with reduced or no-tillage are applied to semiarid soils in comparison to the typical current practice of continuous cotton with tillage.
  • Authors:
    • Iraj Eskandari
    • Abbas Hemmat
  • Source: Aktualni zadaci mehanizacije poljoprivrede. Zbornik radova, 31. međunarodnog simpozija iz područja mehanizacije poljoprivrede, Opatija, Hrvatska, 24-28 veljač 2003
  • Year: 2003
  • Authors:
    • Hutchinson, R. L.
    • Boquet, D. J.
    • Paxton, K. W.
  • Source: Louisiana Agriculture
  • Volume: 46
  • Issue: 2
  • Year: 2003
  • Summary: Studies were conducted in Louisiana, USA, between 1987 and 2002 to determine the effects of tillage practices (no-till and surface till), cover crops (winter wheat, winter hairy vetch and volunteer winter native (fallow) vegetation) and nitrogen rates (0, 35, 70, 105 and 140 pounds per acre) under rainfed or irrigated conditions on cotton growth and yield. Following a cotton crop and without additional fertilizer, the native, vetch and wheat cover crops produced an average 1054, 2054 and 4045 pounds above-ground biomass per acre, respectively. Nitrogen concentration of the cover crop vegetation averaged 2.0, 4.0 and 1.5% in native, vetch and wheat, respectively. The total nitrogen in the cover crop biomass averaged across year, tillage regime and nitrogen rate was 27, 90 and 38 pounds per acre in native, vetch and wheat, respectively. Initially, lint yields in surface-till and no-till were similar but, after five years, no-till yields were higher. No cover crop + tillage treatment recorded the lowest yield. Savings in equipment and labour costs increased the returns for cotton grown with no-till practices. Cotton following vetch needed no nitrogen fertilizer. Cotton following wheat required high nitrogen rates for optimum yield. At the optimum nitrogen rate, all tillage cover crop regimes produced similar yields. Lint yields were lower in rainfed than irrigated conditions. Wheat cover crop was more beneficial to yield in rainfed than irrigated cotton. No-till + wheat cover crop recorded the highest yields and returns from rainfed cotton. No-till cotton produced yields similar to or higher than cotton planted in surface-till treatments.
  • Authors:
    • Flury, M.
    • Huggins, D. R.
    • Bezdicek, D. F.
    • Fuentes, J. P.
  • Source: Soil & Tillage Research
  • Volume: 71
  • Issue: 1
  • Year: 2003
  • Summary: Understanding the fate of soil water and nitrogen (N) is essential for improving crop yield and optimizing the management of water and N in dryland cropping systems. The objective of this study was to evaluate how conventional (CT) and no-till (NT) cropping systems affect soil water and N dynamics. Soil water and N were monitored in 30 cm increments to a depth of 1.5 m for 2 years at growers' fields in two different agroclimatic zones of Washington State (USA): (1) the annual cropping region with a mean annual precipitation of more than 500 rum (Palouse site) and (2) the grain-fallow cropping region with mean precipitation below 350 mm (Touchet site). In each zone, a CT and a NT cropping system were chosen. All sites had an annual cropping system, except for the CT site in the drier area, which was under a traditional winter wheat/fallow rotation previous to the study. At Palouse, the volumetric water content in the top 1.5 m of the soil throughout the year was about 0.05-0.1 m(3) m(-3) less under CT as compared to NT, indicating improved seasonal accumulation and distribution of soil water under NT. Cropping systems modeling indicated, that during winter, surface runoff occurred in the CT system, but not under NT. The differences in soil water dynamics between CT and NT were mainly caused by differences in surface residues. Dynamics of NO3--N at Palouse were similar for NT and CT. At Touchet, differences in soil moisture between NT and CT were less than 0.05 m(3) m(-3). Under NT, high levels of NO3--N, up to 92 kg NO3-N ha(-1), were found after harvest below the root zone between 1.5 and 2.5 m, and were attributed to inefficient use or over-application of fertilizer. In both climatic zones, grain yield was positively correlated with evapotranspiration.
  • Authors:
    • Harrington, L.
    • Jain, M. C.
    • Robertson, G. P.
    • Grace, P. R.
  • Source: Improving the Productivity and Sustainability of Rice-Wheat Systems: Issues and Impacts
  • Volume: ASA Special Publ
  • Year: 2003
  • Summary: Arable lands in the Indo-Gangetic Plains are already intensively cropped with little scope for expansion because of the competing end uses of land for urbanization and industry. Evidence from long-term experiments in the region indicates that cereal yields are declining, which is in stark contrast to the needed increases in production to meet population demands in the future. The intensification of rice-wheat rotations has resulted in a heavy reliance on irrigation, increased fertilizer usage, and crop residue burning, which all have a direct effect on the variable that most affects global climate change - emissions of greenhouse gases. We estimate that the CO 2 equivalent emissions from a high-input conventionally tilled cropping system with residue burning and organic amendments would equal 8 mg C or 29 mg CO 2 per year if applied to 1 million hectares of the Indo-Gangetic Plains. In a no-till, residue-retained system, with 50% of the recommended NPK application, the total emissions would equal 3.7 mg C or 14 mg CO 2 per year, an effective halving of emissions as we move from a high- to low-input system with improved nutrient use and environmental efficiency. The transition to intensified no-tillage systems, with recommended fertilizer levels, can be both productive and environmentally sound in a world that is rapidly becoming aware of the significant effects of global climate change in both the short and long term.