Topdressing turf is an old concept dating back to the old golf course at St. Andrews. Up until recently, the instant gratification and convenience for homeowners, and the profits enjoyed by lawn care companies, meant that modern chemical practices triumphed over the old art of manually spreading compost on the lawn. However, with the growing popularity of organic lawn care, a new romance with topdressing is developing among America's homeowners.
The Practice of Topdressing
Topdressing a lawn is the process of adding a thin layer of material over the grass. Typically, 1/4 to 1/2 inch of compost or another soil amendment is spread across the lawn with shovels, in a throwing action. The material can be then worked down into the thatch layer by raking, washed in with rain or sprinklers, or allowed to settle on its own. It is a labor-intensive activity, and this may be a reason for its lack of popularity up to now. There are motorized top-dressers and compost spreaders available, but they are costly machines, especially for a device that is rarely used. Lawn care companies sometimes offer a topdressing service, but sometimes reluctantly, since it is viewed as a labor-intensive inconvenience that does not have a large profit margin. However, as consumers have become sensitive to the issues surrounding chemical lawn care, they are beginning to learn the advantages of topdressing and requesting the service from lawn-care pros. Many are learning how to do it themselves.
Benefits of Topdressing
Topdressing's benefits are so numerous, it's hard to understand why it is not the foundation for every lawn care program. As a soil amendment, topdressing can improve soil biology by adding organic matter and the beneficial microorganisms found in compost. Soil structure and drainage can be modified by topdressing with sand or other corrective materials. Topdressing regularly can smooth out bumps caused by worm castings and encourages a dense, lush lawn. Topdressing reduces lawn stresses, helps keep thatch under control, and acts as a long-term natural fertilizer. Adding organic matter to a lawn by topdressing with compost is arguably the most beneficial cultural practice that the science of lawn care has to offer.
The Best Materials for Topdressing
Topdressing materials vary greatly and are usually dictated by budget and the needs of the lawn. Most topdressing is performed with compost, which can vary in quality and can be expensive. Compost should be made from the appropriate ratios of wet and dry materials and should be fully "cooked"—highly decomposed, High-quality finished compost is dark and rich and contains a variety of organic materials with few fillers such as sawdust or loam. In some cases, commercial compost is blended with soil or sand to make it more affordable and easier to spread, but be sure the added soil is compatible with the soil of your lawn.
Good topdressing compost is not always easy to find. Some sources try to save money by selling the compost too early, before it has sufficiently cooked, or by using too much filler and and not enough finished compost in the mixture. While it is fine for the topdressing mixture to have some amount of organic material that has not yet decomposed, too much filler negates the benefits of topdressing. In other words, always buy your compost for topdressing from a reputable source.
Sand is sometimes used as a topdressing material on lawns with heavy, clay soils or drainage problems. Usually applied after aerating, the sand fills in the holes and over time can alter the structure of the soil to allow for better drainage and a healthier grass.
How to Topdress
Manual topdressing is hard work, requiring shoveling, moving, and spreading piles of compost or other topdressing materials. The results make the hard work well worthwhile, however. Traditionally, topdressing is spread over the lawn by the shovelful, using a motion that resembles a hockey player swinging at a puck. Fling the compost with a smooth, sweeping motion aimed at spreading the material as evenly as possible to a depth of 1/4 to 1/2 inch. Follow this by lightly raking the lawn to ensure that the topdressing is evenly distributed. Watering immediately will help settle the material and keep it in place.
Motorized topdressing spreader machines are also available to make this work easier. Power spreaders consist of a hopper to hold the material and a motorized belt to move the material through the hopper to a spinning disc that spreads it on the lawn. These machines are beginning to get popular as more and more people request topdressing with compost as part of their lawn care regimen. Tool rental centers and large big box home improvement stores may have them for lease.
It's a good idea to perform topdressing in conjunction with other cultural practices, such as aerating, de-thatching, and overseeding. Topdressing after aerating and overseeding is the ideal trio of lawn care practices, sure to create a healthier lawn. The aerating opens up the soil, allowing for better air and water movement and reduced compaction. The aeration holes, in turn, provide the perfect environment for overseeding, allowing newer generations of grass to establish and thrive. Lastly, topdressing with compost helps fill in the holes, covering the seeds and allowing for ideal germination conditions, as well as just the right burst of nutrients for the grass seedlings as they become established.
Topdressing. Sports Field Management Website at Cornell University