Physical and hydraulic properties of rootzone mixes amended with inorganics for golf putting greens

Abstract

A trend to replace peat with inorganic amendments such as calcined clay (CC) and diatomaceous earth (DE) is occurring for athletic fields and golf course putting greens. For laboratory experiments, washed rootzone sand was amended at 15% (v/v) with either Canadian sphagnum peat (CSP), CC, or DE. Amendments reduced the bulk density and increased the total porosity of all mixtures. The DE mixture had the lowest Ksat (41.9 cm h-1), which was attributed to the 2% by weight of particles <0.05 mm in diameter. The inorganic mixtures retained 0.021 to 0.084 cm3 cm-3 less water than the CSP mixture at pressures less than -2.5 kPa. The CSP mixture held significantly more water in the entire profile and in the upper 15 cm compared with the inorganic mixtures and straight sand. Approximately 75% of the total water was lost within the first 15 min after drainage initiation for sand alone and the inorganic mixtures; only 65% was lost in the first 15 min for the CSP mixture. After 24 h of free drainage, the CC mixture lost the most water, while the DE mixture lost the least. Differences among the rootzone mixtures were measured in the first 3 min of drainage, with straight sand and the CC mixture having the greatest flow rate compared with DE and CSP mixtures. After 24 h of free drainage, the gravel layer remained saturated. For improved water retention in the rootzone, CSP remains the preferable amendment to sand when mixed at these ratios.