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<br />Hammond, L.C., and Yuan, T.L., 1969, Methods of measuring water repellency of
<br />soils, in DeBano, L.F., and Letey, John, eds., Water-repellent soils: University
<br />of California, Riverside, May 6-10, 1968, Proceedings, p. 49-60.
<br />This paper presents and discusses the capillary and dynamic capillary rise methods for
<br />determining an apparent advancing soil-water contact angle as a measure of water repellency.
<br />These two approaches allow for the incorporation of wetting time in the measurement, and
<br />provide an essentially instantaneous determination of water repellency. The authors point
<br />out that the current renewed interest in the nature and consequences of water repellency in
<br />soils demands new and improved methods for both assessing water repellency, and
<br />understanding it. They conclude that the complexity of water-repellent behavior in soil will
<br />require several parameters to be characterized.
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<br />Henderson, G., 1981, Physical and chemical aspects of water repellent soils affected
<br />by slash burning at Vancouver, British Columbia labs.]: Vancouver,
<br />University of British Columbia, Faculty of Forestry, M.S. thesis, p. ii-ill.
<br />This study used water drop penetration time and contact angles to characterize soil water
<br />repellency in a Vancouver watershed subjected to slash burning. Hydrophobic extractions
<br />were also analyzed for functional groups using infrared absorption chromatography. Results
<br />indicated that slash burning caused water repellency to increase, with repellent conditions
<br />persisting up to six years after fire. The majority of extracted hydrophobic compounds were
<br />non-polar. Furthermore, infrared absorption analysis revealed that the hydrophobic
<br />substances had both hydrophilic and hydrophobic components. The author suggested that
<br />the hydrophilic end of the organic molecule bonds to soil particles, leaving the hydrophobic
<br />end exposed. When these extracts were added to wettable sand, heat treatments of 2500C
<br />for 10 minutes caused repellency to increase. The sand again became wettable when heated
<br />to 3500C. The author also noted that the method of using water drop penetration time was
<br />more reliable and consistent than the contact angle method to indicate the presence of soil
<br />water repellency.
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<br />Henderson, G.S., and Golding, D.L., 1983, The effect of slash burning on the water
<br />repellency offorest soils at Vancouver, British Columbia: Canadian Joumal of
<br />Forest Research, v. 13, p. 353-355.
<br />This study compared the water repellency of soils from slash bum clearcuts of various ages,
<br />with those in unburned clearcuts, and uncut control plots. Soil texture, were predominantly
<br />sands, sandy loams, loamy sands, and gravely sands. Burned plots tended to exhibit more
<br />repellency than unburned plots, especially in younger (one or two year-old) burns. The most
<br />intense repellency occurred in the upper four centimeters of the soil, and decreased with
<br />depth. Humus samples exhibited severe water repellency. In contrast to other studies,
<br />researchers generally did not observe a surface hydrophilic condition or severe erosion. The
<br />reduced longevity of repellency was attributed to the high precipitation of the region.
<br />However, the authors also caution that repellency may be a chronic feature once established,
<br />since hydrophobic substances are not easily degraded.
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