Methyl bromide is a widely used soil disinfectant that, because of its ozone depleting properties, is being phased out in the EC by 2005. Soil steaming is a well-established system of soil disinfestation and is increasingly seen as a viable option to methyl bromide replacement. Traditional glasshouse steaming techniques create a number of problems because it involves treatment of soil with high-temperature (100-140°C) steam for up to eight hours or more. This not only eliminates unwanted soil-borne pests and diseases, but also creates a ‘biological vacuum’, in which target pests and pathogens may quickly re-enter and luxuriate, perpetuating the need for regular disinfestation. Soil steaming at lower temperatures, e.g. at 70°C, does not normally result in these unwanted side effects, because of the partial survival of the saprophytic microflora population. In this study agricultural soil samples, containing a range of important soil-borne pests and pathogens, were treated with steam in a specially designed laboratory steam-rig. It was found that treatment at 60°C, for a duration of only 3 minutes plus eight minutes ‘resting’ (“low-temperature/short duration soil steaming”) was enough to 100% kill soil-borne fungal pathogens <i>Sclerotinia sclerotiorum, Sclerotium cepivorum, Verticillium dahlia</i>e and <i>Pythium ultimum; </i>potato cyst nematodes <i>Globodera rostochiensis </i>and <i>Globodera pallida,</i> and weeds <i>Chenopodium album </i>and <i>Agropyron repens.</i> When low temperature/short duration soil steaming was compared with a chemical soil disinfectant, using the fumigant dazomet (Basamid) at a rate of 760 kg/ha, both disinfestation methods resulted in 100% elimination of the above pathogens, nematodes and weeds and caused IGR (Increased Growth Response) of lettuce plants. In a further study, using four different soil types at three different matric potentials, it was found that efficacy of low-temperature/short duration steaming is dependent on soil type and soil moisture content, and that treatment of soil in a moist state is more effective than treatment in a dry state, especially when treating fine-textured sand and loam soils. Soil samples containing survival structures of soil pests were also treated with ozone gas in a specially designed ozone treatment chamber, but this did not result in elimination of target organisms.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:288356 |
| Date | January 2003 |
| Creators | Van Loenen, Mariska C. A. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU602318 |
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