ABSTRACT
Conservation of organic soils used for agriculture requires proper regulation and partitioning of water flow in the environment. This chapter reviews the physical 34properties involved in water retention and transfer in drained organic soils. Basic physical properties are bulk density, specific density, porosity, and ash content. Water retention characteristics of organic soils are influenced by the degree of peat decomposition. Water retention characteristics can be derived from other soil properties using pedotransfer functions. The results of saturated and unsaturated hydraulic conductivity measurements must be interpreted in reference to factors influencing their determination. Relationships between concomitant changes in soil moisture and volume during shrinkage are illustrated by characteristic curves. For converting volume changes into crack volume and subsidence, a dimensionless shrinkage geometry factor can be used. The authors investigated:
The influence of moisture content on water repellency
The effect of repellency on field moisture distribution patterns
The spatial variability of bulk density, hydraulic conductivity, moisture retention characteristics, and moisture content at plot scale
Shrinkage characteristics, the shrinkage geometry factor, and parameters describing water repellency should be incorporated into hydrological models examining simultaneously water transport and the subsidence of organic soils.
