Date of Award
Doctor of Philosophy (PhD)
Entomology, Soils and Plant Sciences
Many golf course putting greens and athletic fields are constructed with a medium consisting of a high sand content. Peat is the most common amendment to rootzone sand (RZS). However, a trend to replace peat with inorganic soil amendments (IOSA), such as calcined clay (CC) and diatomaceous earth (DE), is occurring. Laboratory studies were conducted to evaluate physical and hydraulic properties of rootzone mixtures and a field study investigated the potential of IOSA as a replacement to peat. In laboratory evaluations, amended RZS reduced the bulk density of all mixtures, while saturated hydraulic conductivity (Ksat) for the RZS and mixtures of Canadian sphagnum peat (CSP) and CC exceeded USGA specifications. The DE mixture had the lowest Ksat, which was attributed to the 2% by weight of particles <0.05 mm in diameter. Similarly, RZS water retention and drainage were influenced by amendments. In amended sand mixtures, 0.015 to 0.116 cm3 cm-3 more water was retained compared to unamended sand. Of water retained in the rootzone, the peat mixture held >50% in the upper 15 cm, while straight RZS held the least (37.2%). In drainage experiments, approximately 75% of the total water was lost within the first 15 minutes; however, only 65% was lost in the first 15 minutes for the CSP mixture. After 24 hours of drainage, the CC mixture lost the most water (5.9 cm). Pressure potentials were also measured during drainage. For all mixtures, within 5 minutes of drainage, pressure potentials were negative in the surface 20-cm and positive below the 25-cm depth, indicating saturation. Twenty-four hours after drainage, positive pressure potentials were measured in the gravel layer at the 35-cm depth. In field evaluations of rootzone mixtures on turf grass growth and the rootzone environment, bentgrass (Agrostis palustris Huds. X A. sto/onifera L. 'L-93) seeded into plots amended with peat became established 3 months prior to plots with IOSA and 15 months prior to straight RZS plots. Lower bulk densities were measured in the upper l 0- cm of field cores for amended plots. Also, soil surface strength of peat amended plots were 13 to 31 % lower than RZS and IOSA amended plots. Resistance to penetration in the lower 20 to 30 cm depths ranked in the order of CC> DE> RZS > CSP. The capacitance probe (CP) has been used in mineral soils but not in sand-based, rootzone mixtures to measure soil water content. In laboratory studies, the CP underestimated water content as compared to gravimetric methods; however, linear calibration equations were developed for each mixture. CP readings were unaffected by soil bulk density, but were influenced by amendments. Because of differences between calibration equations for each rootzone mixture, further investigation of the CP is necessary for usefulness as an irrigation tool. Due to greater water retention, lower flow rates, reduced bulk densities, improved turfgrass establishment, and lower impact absorption characteristics, it appears peat remains the best amendment for USGA specification sands.
Waltz, Freddie C. Jr., "The Influence of Peat and Inorganic Amendments on Physical Properties of Sand-Based Rootzones" (2001). All Dissertations. 2653.