Physical Properties of Three Sand Size Classes Amended with Inorganic Materials or Sphagnum Peat Moss for Putting Green Rootzones

Abstract

Modern putting green rootzones are typically constructed using sands to avoid compaction and facilitate rapid drainage. Sands are often amended with organic matter (OM) such as sphagnum peat moss (SP) to increase moisture holding capacity. However, OM decomposition into finely divided material may negatively affect long-term soil physical properties. Inorganic amendments (IAs) having high water retention may be more suitable because of their resistance to biodegradation. A laboratory study determined the physical properties [bulk density, saturated hydraulic conductivity (Ksat), water retention, and pore size distribution] of three USDA sand size classes (fine, medium, and coarse) with and without amendment. Amendments used were calcined clay, vitrified clay, extruded diatomaceous earth, a processed zeolite, and SP. Amendments were tested at two incorporation rates (10 and 20% v/v), and in situ in 30-cm-deep rootzones at two incorporation depths (15 and 30 cm). Bulk density decreased, total porosity increased, and Ksat declined with amendment rate, but varied considerably depending on amendment, sand size, and incorporation depth. The Ksat was high for all mixtures, averaging 250 cm h−1, probably because of the very uniform sands. On the basis of standard pressure plate methods, IAs increased total water holding capacity (WHC) of all three sands but did not increase available water. However, a unique bioassay for available water indicated that porous IAs may contain appreciably more available water than measured by the pressure plate technique. Although the IAs significantly altered the physical properties of the three sands, they were not as effective as SP at improving water retention in coarse-textured, drought-prone sands.