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<br />Bond, R.D., 1968, Water repellent sands, in 9th International Congress of Society of
<br />Soil Science, Adelaide, Australia, 1968, Transactions, v.l, p. 339-347.
<br />This paper presents some preliminary research into the phenomenon of water-repellent soils
<br />in Australia. Research was directed toward the evaluation of sandy, water-repellent pastures
<br />in two districts of South Australia. Trenches excavated during the growing season revealed
<br />that dry, water-repellent sections of the prof11e corresponded to patches devoid of vegetation
<br />on the surface. Conversely, wet areas were occupied by vegetation. Repellency, in some
<br />instances, was as deep as two feet. Two techniques were employed to measure the
<br />repellency. One approach was to measure the contact angle of water drops from enlarged
<br />photograph prints. The other method involved use of the capillary rise technique for
<br />indirect measurement. In an attempt to remedy water repellency in some agricultural soils,
<br />the vegetation was replaced with another group of plants. Repellency decreased, but only
<br />temporarily. Within a few years, the condition had returned to the same degree of severity.
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<br />Bond, R.D., 1969a, Factors responsible for water repellence of soils, in DeBano, L.F.,
<br />and Letey,John, eds., Water-repellent soils: University of California,
<br />Riverside, May 6-10, 1968, Proceedings, p. 259-264.
<br />This author attributes water repellency of sand in Australia to organic f1lms produced by
<br />fungi growing in the soil. The composition of these organic f1lms is unknown, but they are
<br />not oil nor waxes. The effect of the f1lms is reduced by dilute acid and alkali. The intensity
<br />of repellency in the fIeld varies with the species of fungi in the soil, and with the season
<br />when the soil is tested.
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<br />Bond, R.D., 1969b, The occurrence of water-repellent soils in Australia, in DeBano,
<br />L.F., and Letey, John, eds., Water-repellent soils: University of California,
<br />Riverside, May 6-10, 1968, Proceedings, p. 1-6.
<br />This paper introduces some of the factors that affect water repellency in Australian soils.
<br />The author suggests that a low clay content is the most important soil condition to have
<br />naturally occurring water repellency (usually less than 7% in Australian soils). In fact, the
<br />discussion summary that follows the paper mentions laboratory burning experiments in
<br />which sand became water repellent more readily than soils having clay contents of 10% to
<br />15%. The author also states that the total organic matter content has no effect on the degree
<br />of water repellency, but that plant residue must be present for the condition to develop.
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<br />Bond, R.D., and Hammond, L.C., 1970, Effect of surface roughness and pore shape
<br />on water repellence of sandy soils: Soil and Crop Science Society of Florida
<br />Proceedings, v. 30, p. 308-315.
<br />This investigation determined the relationship between real contact angles on individual.sand
<br />grains and the apparent contact angle resulting from a collective mass of sand grains. The
<br />paper included SEM images of contrasting surfaces on wettable and water repellent sand
<br />grains, as well as water drop and menisci shapes. Contact angles on water-repellent sand
<br />grains were usually found to be less than 600, implying that the 1200 contact angles noted on
<br />water-repellent sand masses were the result of porosity. Researchers concluded that, in view
<br />of the low contact angles observed on individual sand grains, substances do not need to be
<br />highly water repellent in order to impart a significant repellency to a soil or sand mass.
<br />Consequently, a much larger range of organic substances have the potential to cause water
<br />repellency.
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