Sub-Root Zone Layering: Effects on Water Retention in Sports Turf Soil Profiles
- D. H. Taylor ,
- S. D. Nelson and
- C. F. Williams
Sports turf areas are often constructed by placing a root zone soil mixture over coarse-textured layers such as sand or gravel. The objective of this research was to determine the degree to which drainage from and water retention in soil mixtures were affected I~.y properties of the underlying layers. In a laboratory experiment, soil water matric potential energies (Ψm) and mass water contents (θm) were measured to characterize the water relations during and after 48 h of drainage for four soil mixtures when placed over the following subsurface layering treatments: 50 mm of sand over 100 mm of gravel., 150 mm of gravel, 150 mm of sand, and loam soil. For the three treatments composed of coarse-textured subsurface layers, soil water matric potential energies at the soil mixture/coarse-textured layer interface after 48 hours of drainage were controlled by the coarse-textm~ed sublayer and varied from about −0.9 kPa for the gravel sublayer to about −2.4 kPa for the sand sublayer. Water retention in the soil mixture layer was greatest for the gravel sublayer, followed by sand over gravel, while sand and soil sublayers resulted in the least water retained. Generally, the increased water retention from gravel and sand over gravel sublayers resulted from creating a wet zone at the bottom of the soil mixture layer rather than increasing water retention throughout the soil mixture. Where coarse-textured materials are used as sublayers in sports turf soils, choice of a soil mixture that drains at the matric potential established at the soil mixture/coarse layer interface is critical to avoid extended periods of saturated soil conditions in the root zone soil layer.
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