Chronic dry spots that occur on the upper reaches of slopes on golf putting greens lead to increased frequency of irrigation to maintain a healthy turfgrass surface. To limit one cause of dry spots, the downslope wicking of water, we investigated the use of subsurface barriers to interrupt the capillary connectivity of the bottom portion of the root zone on a 3.5-m long, laboratory-simulated section of a green having a 5% slope. We evaluated the effectiveness of the barriers on a green constructed with a sand root zone over gravel drainage and on a green constructed with a sand root zone over a geotextile atop a porous plastic grid for drainage. With sand over gravel, the barriers were effective at reducing downslope wicking and the consequential loss of stored water in the root zone on the slope. In the top 0.5 m of the slope, there was 24 mm more water stored in the root zone profile of the green constructed with barriers compared with that in the green constructed without barriers. With sand over geotextile atop a plastic grid, the barriers were effective at reducing wicking of water, but only when the downslope continuity of the geotextile was broken. In that case, there was 35 mm more water stored in the root zone profile at the top of the slope in the green constructed with barriers and a discontinuous geotextile compared with the greens constructed with barriers and continuous geotextile or with sand over gravel and no barriers.
Kevin J. McInnes and James C. Thomas
Keisha Rose-Harvey, Kevin J. McInnes and James C. Thomas
An alternative to the time-tested gravel drainage layer beneath a sand-based root zone of a sports field or golf putting green can be constructed from a geotextile atop a highly porous drainage material or structure. The geotextile serves to support the root zone mixture on the drainage layer whose pores can be too large for the sand to support itself by bridging. In such an application, the geotextile should have high enough strength and resistance to stretching to support the root zone mixture atop the pores of the drainage layer and should contain internal pores of appropriate size to retain the bulk of particles in the root zone mixture and to allow free passage of drainage water and eluviating fine particles. The objective of this study was to determine whether geotextiles selected to meet these criteria affect the drainage rates of sand-based root zones and whether they affect the size of particles lost from the root zone–geotextile systems. In a 1-year laboratory study that made use of 150-mm diameter polyvinyl chloride (PVC) test cells, measurements of drainage rates and saturated hydraulic conductivities were made on replicated combinations of 10 geotextiles and three 300-mm deep root zone mixtures. Size distributions and total masses of particles that passed from the root zones through the geotextiles were measured. Statistical analyses showed that drainage rate, saturated hydraulic conductivity, and size distribution and mass of eluviated particles were unaffected by the properties of the geotextiles. The results gave of no reason to prohibit the use of geotextiles to support sand-based root zones in golf putting greens or sports fields.