Moisture distributions and wetting rates of soils at experimental fields in the Netherlands, France, Sweden and Germany

The variability of soil water content over short distances was studied at s even experimental fields, located in southern Sweden, eastern Germany, sout hern France, and in the Netherlands. The soils all in use as arable land, a re a sandy soil, a stony sandy soil, a loamy sand, a sandy loam, and three clay soils. Samples with a volume of 100 cm(3) were taken at close interval s in trenches at several depths to determine potential water repellency and soil water content. When dry, the topsoils of the Mellby site in Sweden (l oamy sand) and the Vredepeel site in the Netherlands (sandy soil) are water repellent, whereas the soils at the other five sites are wettable, accordi ng to the water drop penetration time (WDPT) test. The variation in water c ontent within short distances was high at most depths at all sites, with di fferences of 7 to 18 vol% within a horizontal distance of only centimeters to decimeters. Drier as well as wetter soil areas were visualized by contou r plots of the soil water content distributions in the transects. Large dif ferences in wetting capacity between samples taken in the topsoil and in th e subsoil at several sites were assessed by measurements of the wetting rat e. In many cases, subsoil samples wetted faster than topsoil samples. The s everity of water repellency of sandy samples from the Vredepeel site increa sed remarkably at oven temperatures above 65 degrees C, The wetting rates o f dried samples from this soil were also evidently influenced by the oven t emperature; samples dried at 25 degrees C wetted immediately and reached so il water contents of 23 to 32 vol% within one hour, whereas samples dried a bove 85 degrees C hardly wetted during 72 hours, as a result of the increas ed water repellency at higher drying temperatures. (C) 1999 Elsevier Scienc e B.V. All rights reserved.