A packed lysimeter experiment to investigate the effect of surface sealing on hydrology and pesticide loss from the reconstructed profile of a clay soil |
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Authors: | CM Heppell AS Chapman VJ Bidwell AA Kilfeather |
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Institution: | Geography Department, Queen Mary, University of London, Mile End Road, London E1 4NS, UK;Environment Agency, Howbery Park, Wallingford OX10 8BD, UK;Lincoln Environmental, PO Box 84, Lincoln University, Canterbury, New Zealand |
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Abstract: | Abstract. A laboratory experiment was designed to assess the impact of surface seal development on herbicide loss from a clay soil. The influence of surface sealing on herbicide loss through vertical macropores and lateral throughflow pathways was of particular interest. Losses of the phenylurea herbicide, isoproturon, increased from 0.025% to 0.5% of the total applied under sealed compared with unsealed conditions, as a result of two different mechanisms. First, an increased flow rate through the A horizon under the wetter, sealed conditions resulted in earlier initiation of, and hence a greater volume of, throughflow containing isoproturon in the lysimeters. Second, increased concentrations of isoproturon in macropore and throughflow under the sealed treatments were attributed to the physical and chemical characteristics of the surface seal. Localized reductions in infiltration capacity, changes in soil composition, and decrease in diffusion depth of herbicide within the surface seal are presented as possible mechanisms by which herbicide losses from the sealed soil lysimeters were enhanced. |
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Keywords: | Lysimeter macropore throughflow subsurface lateral flow herbicide surface seal surface crust |
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