Dissipation of imazapyr, flumetsulam and thifensulfuron in soil |
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Authors: | R W MCDOWELL L M CONDRON B E MAIN F DASTGHEIB |
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Institution: | Department of Geography, University of Cambridge. Downing Place. Cambridge CB2 3EN. UK.;Department of Soil Science (LMC) and Plant Science (FD), PO Box 84. Lincoln University, Canterbury. New Zealand;Department of Soil Science. University of Reading, Whiteknights, PO Box 233. Reading RG6 2DW. UK |
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Abstract: | The degradation of imazapyr, flumetsulam and thifensulfuron applied at 500.40 and 30 g active ingredient (a.i.) ha-1, respectively, to silt loam soil was studied under laboratory and field conditions. Herbicide residues were analysed by a lentil ( Lens culinarits L.) bioassay. Results showed that temperature had a significant effect on herbicide degradation, whereas the impact of soil organic matter ami pH were less well defined. Half-lives for imazapyr, flumetsulam and thifensulfuron in soil samples from the 0-5 cm layer (6.4% organic carbon) at 15 °C were 125, 88 and 5.4 days, respectively, and 69, 30 and 3.9 days at 30°C. In soil sampled from the 15-20 cm layer (3.5% organic carbon) half-lives were 155. 70 and 6.4 days, respectively, at 15 °C and 77, 24 and 4.8 days at 30 °C, A field experiment investigated the degradation and teaching of each herbicide under two precipitation regimes natural precipitation (208 mm), and natural precipitation plus 75 mm irrigation (283 mm) over 4 months to a soil depth of 25 cm. Thifensulfuron degraded rapidly, whereas residues of flumetsulam and imazapyr leached below 25 cm in both the low-and high-precipitasion treatments after 4 months. Significant imazapyr residues were still present in the soil to 25 cm depth after 3 months, A multi-component model for herbicide dissipation was developed and evaluated using data from the laboratory and field experiments. |
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