Capping poorly performing soils with sand seems like a dream scenario for turf managers. The sand is expected to deliver excellent drainage and water infiltration properties, ample aeration porosity and firm playing conditions – but beware of the mirage of the sand cap! Within a few short growing seasons, the benefits of a sand cap can be wiped away if organic matter accumulates to high levels. This scenario is observed all too often on Course Consulting Service visits. High levels of surface organic matter trap water and salts at the surface, which essentially negates the benefits of the sand below.
Before sand capping, test the existing soil physical properties as well as several different sand options. There may be a better method to provide adequate water infiltration and porosity than sand capping. For example, an aggressive sand topdressing program very often delivers much better fairway performance than sand capping. If sand capping is the chosen method, or if your facility already has sand-capped fairways, consider the following strategies to retain or recover the desirable physical characteristics of the sand cap:
- Sand topdressing will be critical in sand-capped areas. Depending on the situation, sand should be applied at rates as low as 15 tons per acre per year to as much as 100 tons per acre per year.
- If you are growing bermudagrass, seashore paspalum or kikuyugrass, consider fraise mowing every two to four years to remove much of the organic surface layer and follow with sand topdressing.
- If fraise mowing is not an option, deploy a combination of light-intensity and aggressive vertical mowing. Another option on warm-season turf is to use a metal spring-tine rake to stand up the turf and follow with aggressive scalping.
These options will improve fairway conditions, but it will often take two or three full growing seasons to see marked improvement. If two to three years is too long to wait for better conditions, consider rototilling the organic matter layer into the sand cap, and perhaps even include the underlying native soil. However, this strategy should be considered with great caution because it could backfire and make conditions worse. That said, I have seen this tactic work extremely well – as recently as this year at Menlo Country Club in California. Measuring physical characteristics of the soil and the sand/organic layer mixed together will be critical information to help guide your decision on tilling.
The potential benefits of a sand cap can be negated if organic matter is left to accumulate on top, and you could wind up with a real mess. Consider this before sand capping approaches or fairways.
West Region Agronomists:
Brian Whitlark, senior consulting agronomist – bwhitlark@usga.org
Cory Isom, agronomist – cisom@usga.org