Analysis of Sand Capping Depth Based on Moisture Retention Curves.

Sand capping is applying a relatively deep layer of sand on top of an existing turf area such as a sportsfield or golf course fairway to improve playability and drainage, whilst providing an acceptable rootzone for turf growth. The depth used for sand capping is very important as if the layer is too deep a dry surface can result, if too shallow poor drainage and waterlogged conditions often occur. Currently, capping depth standards do not exist, although a number of different methods to determine them have been suggested. A selection of methods for establishing sand capping depth were examined utilizing moisture retention curves (MRC’s).

Sand was mixed to meet USGA specifications and MRC’s were created using the Haines method. To create MRC’s volumetric water content of sample was established every 2.5 cm to a depth of 50 cm. MRC’s were used in combination with several methods of establishing sand capping depths in the literature to come up with recommended capping depths. Sand columns were created out of sections of PVC pipe at the appropriate depth for each methodology. Columns were exposed to three drainage regimes using hanging water columns - 0 cm tension represented poorly drained subsoil under sand, 15 cm tension represented intermediate drainage, and 30 cm tension represented well-drained situations. When columns reached equilibrium, they were separated and volumetric water content calculated for each section. Bulk density, saturated hydraulic conductivity, and gravimetric water content were also calculated for the columns.

Results of this study will be discussed at the conference.