Sand topdressing: the history, current knowledge, and new perspectives of its role in organic matter management

Sand topdressing is the practice of applying a thin layer of sand to the surface of a turf. The history of sand topdressing dates back over a century on the Old Course at St. Andrews, Scotland. Sand topdressing is critical for improving root zone physical properties, supporting healthy root systems, and alleviating compaction stresses at the soil surface of highly trafficked turfs. A primary benefit of using non-amended sand for topdressing is to avoid adding additional organic matter when the management objective is to prevent excessive organic matter (thatch) accumulation. However, there is a long-running debate about whether topdressing alone is sufficient for organic matter control. The documentation of organic matter accumulation is limited. Multiple years are often needed for sufficient organic matter to accumulate and enable the detection of differences among topdressing treatments. In a three-year case study on an annual bluegrass (Poa annua) putting green turf, our data suggest that topdressing sand decreases organic matter content on a mass basis by diluting thatch and forming a mat layer. The growth of healthy turfgrass can contribute greatly to organic matter accumulation at the surface of the soil profile. Thus, a successful topdressing program needs consistent applications to match the growth pattern of turfgrass for the local climate. A more comprehensive understanding of organic matter build-up and its subsequent role in soil and plant health is needed. Cultural management solely based on thresholds of organic matter content in turfgrass systems does not acknowledge that other evaluations such as layering, root health, water infiltration, and surface firmness need to be carefully considered before implementing cultivation management practices to reduce organic matter.