Soil attributes related to water repellency and the utility of soil survey for predicting its occurrence.
1994
Harper R.J. | Gilkes R.J.
The incidence and severity of water repellency was related to 5 soil classes (FC I-V), based on the field texture and dry consistence of the soil surface horizons, derived from a soil survey near Jerramungup, Western Australia. Water repellency was most severe on the FC I soils (median clay content 1.5 percent), with 66 percent of samples having water repellency based on the water drop penetration time (WDPT) test greater than 10 s. Water repellency did not occur on the most clayey FC IV (8.1 percent clay) and FC V (22.1 percent clay) soils. Following stratification of Ap horizon soils by 1 percent increments of clay content, highly significant linear relationships occurred between log (water drop penetration time) and log (organic C) for the 1-2, 2-3 and 3-4 percent clay classes, these respectively explaining 50, 35 and 37 percent of the variation in water repellency. The role of organic C in promoting water repellency decreases markedly with increasing clay content. There is a strong geomorphic control of the clay content in the soil surface horizons. Given the effect that clay content has on water repellency, the susceptibility of soils to water repellency can be mapped across farms, with the actual expression of water repellency depending on soil organic matter content, and hence land use. Such discrimination will allow the prediction of water erosion hazard and identify soils requiring amelioration.
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