Topdressing is the act of applying a layer of sand (as thin or thick as can be applied with the correct growing conditions) to a turfgrass stand and brushing, grooming, or irrigating it into the canopy. The purpose of topdressing serves three main goals, as described below.

  1. Reduce surface compaction due to moist thatch layer around plant crowns, stolons, and rhizomes.
  2. Dilute the thatch layer to maintain the balance of percolation rate for water and exchange rate of gasses. That way, the turf doesn’t drown or get choked out by trapped gasses in the profile. 
  3. Help correct surface puffiness and allow for smooth, quality cuts. 

Warm- and cool-season turf topdressing aren’t that different in terms of overall purpose or end goal, as noted above. The differences mainly lie in the aggressiveness in cultural practices (grooming, verticutting, brushing, and aeration), the amount of material used in the process, and timing.

Light dustings of sand can be applied as soon as conditions allow in the spring and continue as late as the growing conditions allow in the fall. Too early or too late can create problems for your turf if it is becoming stressed or unhealthy. These light dustings are done as often as your conditions and level of play allow and are typically on the tail end of the cultural practices of grooming, verticutting, or brushing.

Heavier topdressings are used in the peak of the growing season in concert with core or solid tine aerations. These are the key and most beneficial applications of topdressing. You’re modifying the upper soil structure by removing thatch/organic material and working a large load of sand into channels that greatly improve the water infiltration rate and exchange of profile gasses. This is also a great time to use a coarse (but within your specifications) material to help open up the profile if it’s more wet and compacted. Note that coarser material takes longer to work into the profile than finer material, especially if it did not end up directly in an aeration hole or if it is very coarse. Limit very coarse materials to the process of DryJecting, which can be done along with your core aeration. DryJecting is awesome if you can get it done. The process uses high-pressure water to fracture the soil surface and “inject” sand or other soil profile modification materials, leaving practically no surface disruption and minimal cleanup afterward.

It’s also a good idea to have ISTRC physical properties testing done on your greens and topdressing materials to ensure they meet the USGA sand-based greens construction specifications and physical properties. This is invaluable material to know, especially if you are sand-based. If inheriting greens from a previous manager or on new construction, this testing will let you know of any mismanagement from using out-of-spec materials and the issues potentially looming on the horizon from that. It will let you know where you stand with thatch and organic material and what sands you can safely use that will not bridge or lock up your profile and cause you all kinds of problems.