Evaluation of Water-use in Turfgrass
Type of DegreeDissertation
Agronomy and Soils
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This dissertation examined the response of four hybrid bluegrasses [Texas bluegrass (Poa arachnifera Torr.) × Kentucky bluegrass (Poa pratensis L.)], HB 129 (‘Thermal Blue’), HB 130, HB 328 and HB 329 (‘Dura Blue’) and two tall fescue cultivars (Festuca arundinacea Schreb.), ‘Green Keeper’ and ‘Kentucky 31’, to varying irrigation replenishments. Field experiments were conducted at the Turfgrass Research Facility, Auburn University, AL, from June through September 2005 and a similar period in 2006. Three irrigation treatments were applied based on potential evapotranspiration (ET), viz., 100 % ET, 80 % ET and 60 % ET replacements. The experimental design was a 6 by 6 Latin square with six replicates of each treatment combination within an irrigation block. Tensiometers were installed at 7.5-, 15- and 30-cm depths in the middle blocks of each plot, readings were recorded daily and the values were used to calculate the matric head, water content and water-use values. Turf color quality, root length density and root dry mass of hybrid bluegrasses and the tall fescue cultivars were evaluated. The research showed that the hybrid bluegrasses used less water compared to the tall fescue cultivars. The ranking based on root length density and turf color quality was: HB 329 (best) > HB 130 > HB 328 > HB 129 > Kentucky 31 > Green Keeper. Physical and hydraulic properties of inorganic amendments used in turfgrass root zones were evaluated. The objectives of this study were i) to evaluate and compare the physical and hydraulic properties of un-amended sand (100% sand) and 7 commercially available inorganic amendments used in sand-based root zones, viz., zeolites (Clinolite and Ecolite), calcined diatomaceous earth (Isolite and Axis) and calcined clays (Moltan plus, Profile, and Pro’s Choice), and ii) to evaluate the physical and hydraulic properties of amendment-sand mixtures (15% amendment with 85% sand v/v). The properties analyzed were bulk density, particle density, porosity, particle size distribution, saturated hydraulic conductivity, water retention and available water. All the amendments and amendment-sand mixtures exhibited higher porosity, water retention and available water compared to 100% sand. The values were highest for the calcined diatomaceous earths. A numerical model was applied to simulate soil water movement with root water uptake for a scenario with amendments (15% amendment plus 85% sand v/v), and without amendment incorporation (100% sand). The simulation results showed reduced surface dryness, higher volumetric water content and storage, and higher initial root water uptake rate for the root zones modified with amendments. The highest simulated water storage was observed for root zones modified with calcined diatomaceous earths, especially Axis amendment.