Topdressing is becoming more and more important in the maintenance of quality turf for golf courses and sports fields. There are many questions, ideas, and myths in the industry about topdressing. The following list of frequently asked questions addresses some of these issues. The information comes from a variety of industry sources. If you have questions that are not addressed here, please contact us and we will do our best to help you find the answers.

Our most commonly asked questions are related to topdressing. The following 12 questions should assist you with most of your questions. However, if you cannot find your answer here, or you have questions relating to a different blending area, please submit your question or contact us at 800.424.3443.

Two areas to examine in selecting a topdressing mix are the physical characteristics and the chemical properties. The physical characteristics of the topdressing should be similar to the area being topdressed. That means that particle size distribution should be similar. Similar size particles mean similar porosity and similar percolation rates. Using a topdressing mix that is radically different from the current rootzone can result in layering problems that may cause poor drainage; limit growth through the layer; restrict air, water and nutrient movement into the rootzone; and possibly kill the turf. If you need to change the present rootzone mix and decide to make the change by topdressing, the change should be gradual. A program of frequent, light applications over a period of time will allow a gradual change. It is usually best to use a topdressing mix that is physically similar to the current rootzone mix.
The second important aspect of the topdressing mix is the chemical properties. Is the pH level acceptable? Most plants, especially turf grasses, grow best in a pH range of 6.0 to 8.0. The growth is usually limited by soils that are either too acidic or too alkaline. A single topdressing outside this range may not affect the overall pH level a great deal, but repeated applications will adjust the pH up or down far enough to affect the turf growth. What is the cation exchange capacity or ability to hold and supply nutrients? Turf grass needs many nutrients for growth and if the rootzone can hold on to these nutrients for the turf rather than letting them leach out, the turf will need less fertilizer. That means less work and less expense. Does the topdressing have organic matter or other nutrients to provide for the turf growth? Plants require more than just air and water to grow. The soil can only provide part of the required nutrition and the available nutrients will vary. But all rootzones need supplements. These may or may not be added as part of the topdressing. For instance, carbon, nitrogen, some minerals and humic acid are all available in various organic materials. A good organic material will provide some of the needed nutrients and also help hold nutrients and fertilizers as they are added. It is important to determine the chemical requirements of your turf and adjust your topdressing to fit these requirements.
There are many reasons to add an amendment to sand for your topdressing. The pH level of straight sand can fluctuate a great deal. Sand does not hold water or nutrients very well. Over time your greens will lose the ability to hold water and fertilizer. This will add up to additional costs. A straight sand rootzone will allow water to run right through it and this will leach out many other nutrients. This is not only costly, it is bad for the environment. Sand is usually inert and has no microbial activity. A lack of microbial activity can result in disease problems, thatch problems or other problems. Sharp sands can damage the turf. Although this may be the cheapest method initially, long-term use of straight sand as a topdressing can be very expensive.
It is true that you can add almost every nutrient and characteristic you need to grow turf. The difference is the amount of work needed and the long-term cost. Using a good quality organic material will pay for itself many times over in saved labor and wasted chemicals or water. A side benefit is keeping all those wasted chemicals out of the groundwater system. Nature, your staff and your customers will thank you.
There are several easy ways to use an organic material in your topdressing. The easiest way is to buy a mix already blended from the sand company. Many sand companies around the country have started blending topdressing for their clients. The added expense of the ready-made topdressing is easily offset by the labor saved. Another easy way is to buy an organic material that mixes easily. DAKOTA peat can be bucket mixed quickly and thoroughly because of its fine texture. Bucket mixing DAKOTA will result in a mix more thoroughly blended than other amendments blended with a mechanical mixer. A third way to make topdressing easier is to buy a combination blender/topdresser. The machine will take the separate peat and sand and mix them as it spreads the mix.
It has been found that microorganisms in the soil can benefit plant growth in many ways. Some microorganisms help transform nutrients, such as nitrogen, into forms that the plants can use. Many bacteria produce hormones that stimulate plant growth. Other microorganisms help control thatch problems by assisting in degradation. It is also thought that there is a group of microorganisms that help plants defer or resist diseases. More benefits are being discovered all the time. The high microbial activity is why a product like DAKOTA peat is far superior to a sphagnum peat or other amendment with low or no levels of microbial activity.
The danger of diseases or weed seeds being part of the organic material can vary depending on the source of the organic material. Less-decomposed organic materials have a higher chance of causing problems than highly decomposed materials. For instance, DAKOTA peat is highly decomposed, is very clean and has never had disease or weed problems associated with its use.
There has been a great deal of research done in the area of organic material and soil amendments. The actual needs of your course will determine a great deal of what you should be looking for. Availability and price will be other key conditions. One thing to remember about pricing: low initial investment price is not usually the best product to use. It will usually not end up doing the job that is needed. A product that will save money in other areas can often more than make up for a higher initial investment. For instance, DAKOTA peat is not usually the least expensive option when purchasing amendments. However, money saved on irrigation, fertilizer, and labor will more than pay the difference in initial investments. And the compliments you will receive for the way the greens look will be a nice added bonus.
The frequency of topdressing will depend on the reasons for topdressing and the needs of your turf. If your greens were built with high quality materials and maintained properly, the topdressing is probably only needed for cosmetic reasons, to make sure you have a good level playing surface and maintain the current rootzone. In a case like this, two to four light topdressings throughout the season will be sufficient. If you have more serious concerns about your greens, more frequent topdressings may be needed. You may need to topdress every 3-4 weeks throughout the entire season to help rebuild problem areas or greens. This frequency may need to be maintained for several years to replace or recreate the rootzone without having to completely reconstruct the green.
Like the previous question, the answer will depend on your individual circumstances. However, most people now recommend using light coatings of topdressing and increasing the frequency if large amounts of topdressing need to be applied. The average 18-hole golf course will probably need to use approximately 50 tons of topdressing mix for each application.
Aeration is used to combat a variety of turf problems. Commonly, aeration is used if you have compaction problems and occasionally for thatch or layering problems. Topdressing after aeration will allow the new rootzone material to penetrate the problem area. In time and with repeated applications, this should help relieve these problems. However, it is not necessary to aerate before every topdressing application. If your greens do not have a problem that can be helped by aeration, like needing to smooth the greens, aeration is not required.
Some organic materials can add to a thatch problem. Thatch is caused by a buildup of undecomposed organic materials. This layer will interfere with air and water movement. Often, this buildup can be traced to a lack of microbial activity. Many organics, like sphagnum peat, rice hulls, and sawdust, are in the early stages of decomposition. When these are added to turf with decaying organic matter from the turf, the problem can be compounded. Other organics, like DAKOTA peat, are heavily decomposed and have a great deal of microbial activity. This microbial activity will help relieve the thatch problem over time.
Unfortunately, topdressing can’t help fight fairy rings. Fairy rings are caused by fungi, usually mushrooms. The fungi start from microscopic spores. These spores will grow under warm conditions and are usually caused by some kind of organic material that has not decomposed a great deal. This could be an organic material such as sawdust, wood chips, sphagnum peat, compost, or any other organic material that has not had time to decompose. The growing fungi, also known as mycelium, will grow through the soil away from the original spore. They usually grow in somewhat of a circle, hence the term "fairy ring". The fungi will use most of the nutrients that the turf would need to grow, and also can form a mass that limits air and water movement. These factors combine to kill the turf where the mycelium is growing. The best way to get rid of the problem is to remove the mass of mycelium. Cut out the area of dead turf deep enough to remove the offending fungi. The mycelium can usually be seen as white or off-white threadlike materials. Fill the problem area with a clean rootzone mix that contains a heavily decomposed organic material, and then seed or sod the area. The other option is to kill the fungi with chemicals. This will sterilize the area treated and make it difficult to reestablish turf growth. It is also hard to determine if the entire mass has been killed. If it is not, the remaining mycelium will continue to grow.