Sandcapping, Subsoil, and Irrigation Effects on Bermudagrass Fairway Performance.

The objectives of this 3-yr project are to: 1) Assess season-long turf quality and root distribution of Tifway bermudagrass fairway turf constructed at various depths of sand capping atop both fine sandy loam and clay subsoils, 2) Determine how sand capping x subsoil combinations influence root zone soil moisture and irrigation frequency requirements, 3) Determine the temporal and spatial dynamics of salts through measurement of electrical conductivity and subsoil sodicity in response to sand-capping x subsoil x irrigation treatments, and 4) Initiate a summer dry-down in year 3 to evaluate how sand cap x subsoil treatments affect turf’s ability to tolerate and survive 60-days with no supplemental irrigation. In July 2014, construction of a 0.2 ha (15.2 m x 121.6 m) research fairway was initiated at the Texas A&M Turfgrass Ecology Field Laboratory in College Station, TX. To evaluate the effects of subsoil texture on sandcap performance, the site was divided into a native Boomville fine sandy loam and clay subsoils (strongly aggregated, clay textured subsoil imported from off-site). Subsoils were graded and firmed to produce a final 2% sloping turtleback spanning the entire length of the fairway.  Twelve irrigation zones were installed for testing effects of irrigation frequency x sandcap x subsoil on various parameters during the project. A washed brown concrete sand produced by a local sand company was selected for construction of sandcaps.  Particle size distribution analysis indicated the sand possessed 24.8% fine gravel, 18.5% very coarse sand, 17.1% coarse sand, 23.5% medium sand, 10.3% fine sand, and 2.7% very fine sand.  Total silt plus clay within the sand was less than 3%. Given the capillary properties of this sand, an 20.3 cm sandcap would typically be recommended to allow for ideal gas/water filled porosity if the sandcap were placed above a capillary barrier such as gravel. When placed atop fairway soil, the hydraulic properties of the soil may lead to appreciable alteration of that recommendation. Sandcap treatments (15.2 x 3.6 m) were constructed to 0, 5.1, 10.2, and 20.3 cm final depths and firmed using a mechanical tamper. A 1.2 m buffer was provided between plots to accommodate differences in sandcapping depths of adjacent plots.  Plastic liner was also inserted along plot borders to prevent lateral movement of water between plots.  On 2 September 2014, the study site was hand-sprigged with Tifway bermudagrass, heavily topdressed, rolled, and fertilized weekly. One month after sprigging, volumetric water content in the upper 5.1 cm depth was determined at multiple points along the slope in each plot.  Percent establishment was quantified both visually as well as through light box imaging. Data indicated that more rapid establishment occurred within shallower sandcap depths, likely due higher volumetric water content and less intermittent drying at the soil surface. Effects of the treatments on percent green cover and rooting charateristics are being evaluated during the 2015 season.