Saturday, 15 July 2006
137-4

Changes of Nonrigid Pore Structure upon Predrying Intensity and Frequency.

Xinhua Peng and Rainer Horn. Institute of Soil Science and Plant Nutrition, Olhausenstr 40, Christian Albrecht Univ, Kiel, 24118, Germany

Knowledge of pore structure is fundamental to model hydraulic properties. However, pore structure of nonrigid soils varies with soil water content and/or matric potential. We investigate the changes of pore structure of four soils (Eutric Histosol, Histic Gleysol, Calcic Gleysol, and Dystric Gleysol) after predrying intensity and frenquency. Soils are subjected to four levels of predrying intensity (1000hPa, 1000hPa30°C, 30°C1000hPa, and 30°C) from one up to three cycles, and followed by suction at -6, 15, 30, 50, 100, 500 kPa on ceramic plates. Water content and soil shrinkage are determined. Pore size distribution is calculated from Water Retention Curve (WRC). The changes of pore size and magnitude are determined as compared to the non-predrying soils. Soil shrinkage in relation to water content and matric potential is modeled and the four shrinkage phases (structural, proportional, residual, and zero shrinkage) are characterized as well. We also evaluate the unsaturated hydraulic conductivity (Ku) when taking into account soil shrinkage. The obtained data will explain the changes of pore structure as a function of soil shrinkage and how much they influence hydraulic conductivity.

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