In This Chapter

Soil Water Content and Water Potential Relationships

Authored by: Dani Or , Jon M. Wraith , David A. Robinson , Scott B. Jones

Handbook of Soil Sciences Properties and Processes

Print publication date:  November  2011
Online publication date:  November  2011

Print ISBN: 9781439803059
eBook ISBN: 9781439803066
Adobe ISBN:


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Water in soil occupies pore spaces that arise from the physical arrangement of the particulate solid phase, competitively and often concurrently with the soil gas phase (Chapters 1, 2, and 8). While hidden from casual view, substantial volumes of water are commonly stored in soils. For example, one hectare of medium-textured soil 1 m deep and having field capacity water content of 20% by volume may store sufficient water to fill 4000 200 L barrels. This reservoir serves as a resource pool for plant growth and a substantial buffer in areas having scattered or sporadic precipitation. Other soil organisms, many of which are beneficial, especially to biogeochemical cycling, also rely heavily on the water-holding characteristics of soils for their existence. On the other hand, soil water is a highly dynamic entity, exhibiting substantial variation in both time and space (Western et al., 2002). This is particularly true near the soil surface and in the presence of active plant roots. Changes in soil water content and its energy status affect many soil mechanical properties including strength, compactibility, and penetrability, and may cause changes in the bulk density of swelling soils. The liquid-phase characteristics affect the soil gaseous phase and the rates of exchange between these phases, as well as other important soil properties such as the hydraulic conductivity that governs the rate of water and soluble chemical flow.

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