Popis: |
An Inceptisol (Andept) from Ecuador, an OOxisol (Ustox) from Columbia and a Mollisol (Udoll) from the U.S.A. were studied. The clay in the Andept was >85% amorphous with allophane being predominant. The Ustox contained sesqui-oxides of iron and aluminum and kaolinite, while the Udoll contained hydrous mica, quartz and kaolinite in the clay fraction. The water retained at all matric potentials >−100 kPa decreased in the order Andept, Udoll, Ustox. The mean wet strength declined approximately in the order Andept = Ustox > Udoll. Hydraulic conductivity decreased with aggregate size. The Ustox and Andept were more stable under rainfall impact than the Udoll. Greater stability was reflected in higher infiltration rates, lower run off, less soil splash and soil movement in run off water. The differences in physical behavior were clearly related to the widely different characteristics of the clay fraction. The physical properties of the three soils studied have important implications as to their management. |