| heal.abstract |
Preferential flow is implicated as one of the causes of groundwater contamination with agrochemicals. Although preferential flow is a natural process, on turfgrass surfaces, it may be enhanced by mechanical aeration that creates surface perforations similar to macropores. Aeration effect on pesticide mobility is not well known, and therefore, the objective of this paper is to visualize the infiltration flow paths from aerated turfgrass systems as influenced by soil moisture and sand content. Forty-eight lysimeters located in a greenhouse were established to simulate greens constructed of sand or existing sandy clay soil. The movement of blue dye was observed under two moisture regimes for three aeration practices (shallow hollow tines, deep drill, and high-pressure water injection) and a nonaerated control. After the dye was applied, stained cross sections taken at 5-cm intervals were traced on transparent sheets and digitized. Analyzing the dye patterns revealed three types of flow: matric flow, preferential flow through the man-made aeration macropores, and fingered flow due to hydrophobicity. Hydrophobicity induced by the grass cover caused ponding which caused water either to infiltrate in the man-made macropores or formed fingers especially when infiltration through the macropores was limited. Hydrophobicity was most severe for the dry treatments. Wet sand was not hydrophobic and water infiltrated as matric flow. In all cases, the dry sandy clay soils exhibited more preferential flow than the sand, independent of aeration treatment. The results show that the best time to apply agrochemicals on cultivated turfgrass sites is shortly after irrigation or on wet soils to reduce the sod hydrophobicity. However, this was not the case for deep-drill application on sandy clay soil. Copyright © 2007 by Lippincott Williams & Wilkins Inc. |
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