EWRS Herbicide-Soil Working Group: Collaborative experiment on simazine persistence in soil |
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| Authors: | A WALKER R J HANCE J G ALLEN G G BRIGGS YUH-LIN CHEN J D GAYNOR E J HOGUE A MALQUORI K MOODY J R MOYER W PESTEMER A RAHMAN A E SMITH J C STREIBIG N T L TORSTENSSON L S WIDYANTO R ZANDVOORT |
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| Institution: | National Vegetable Research Station, Wellsesbourne, Warwick, U.K.;ARC Weed Research Organization, Begbroke Hill, Yarnton, Oxford, U.K.;East Malling Research Station, East Malling, Maidstone, Kent, U.K.;Rothamsted Experimental Station, Harpenden, Herts, U.K.;National Taiwan University, Taipei, Taiwan, Republic of China;Agriculture Canada, Research Station, Harrow, Ontario, Canada;Agriculture Canada, Research Station, Summerland. B.C., Canada;Institute di Chimica Agraria e Forestale, Universita di Firenze, 50144 Firenze, Italy;International Rice Research Institute, PO Box 933, Manila, Philippines;Agriculture Canada, Research Station, Lethbridge, Alberta, Canada;Biologische Bundesanstalt für Lund und Forstwirtschaft, D-3300 Braunschweig, West Germany;Ruakura Soil and Plant Research Station, Private Bag, Hamilton, New Zealand;Agriculture Canada, Research Station, Regina, Saskatchewan, Canada;Royal Veterinary and Agricultural University, DK-1871 Copenhagen, Denmark;Swedish University of Agricultural Sciences, Uppsala 7. Sweden;BIOTROP. PO Box 17, Bogor. Indonesia,;Centre for Agrobiological Research, PO Box 14, Wageningen, The Netherlands. |
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| Abstract: | The effects of soil temperature and soil moisture content on the rate of simazine degradation were measured in the laboratory in soils from sixteen sites located in several different countries. First-order half-lives under standard incubation conditions were significantly correlated with clay content, organic carbon content and soil pH in a multiple linear regression. The temperature dependence of degradation was similar in the different soils whereas the moisture dependence showed considerable variation between soils. Persistence of simazine was also measured in the same soils in the field and at live additional sites. Weather records from the different sites for the periods of the Held experiments were used in conjunction with constants derived from the laboratory data in a computer program to simulate persistence in the field. In general, the model overestimated residues in the field. About half of the calculated residues were within 25% of those observed, an accuracy sufficient for practical purposes, but on several occasions the discrepancies between calculated and observed residues were greater than 50%. Possible reasons for the discrepancies and requirements for further experiments are discussed. |
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