Topdress Overview 

  The practice of topdressing golf greens has been around for decades.  More recently this practice has been extended to golf fairways and sports fields.   While there is almost universal agreement about the benefits of topdressing, there is not a universal sand that is appropriate for all topdress needs. 

  This newsletter will hopefully aid those seeking or supplying topdress sands to select the right sand for the job.  We will not discuss when to topdress or whether or not other amendments should be added.  Just some basic information on sand selection.

  Topdress sands are not one size fits all.   For example, a sand that is ideal for a native soil based field may be detrimental to a sand based field.  There is, however, a general rule of thumb that is applicable for most all topdress efforts.  The sand that is selected for topdressing should be of the same particle size or slightly coarser than the material to be topdressed.   This reduces the potential for layering.

   Layering occurs when a discrete layer of sand or thatch is formed over the rootzone.   This discrete layer, which usually arises when too fine of a sand is used for topdressing,  then acts as an impediment to the movement of water and oxygen.  In its most drastic form, layering can totally shut down the internal drainage of a turf system.

  As discussed, we don’t recommend using a sand that is too fine.  What about coarse sands?  Coarse sands may be desirable because of their good drainage, but very coarse sand (greater than or equal to 1 mm in size) can present problems.  The larger particles are particularly problematic for putting greens.  These particles can  be difficult to work into the turf canopy.  Due to ultra-low cutting heights, greens mowers are especially prone to damage from gravel particles that may remain on the surface after topdressing.

Testing of Topdress Sands a Must

  The topdress sand must be compatible with the existing rootzone material.  Topdress/rootzone compatibility is determined by performing a particle size analysis  on the existing rootzone material and the proposed topdress.  The testing lab can then comment on the suitability of the topdress sand for the soil.  Additional tests, such as, infiltration rate and pH may also be performed. Since topdressing is often performed to aid in water movement, a high infiltration rate is desirable.  Sands with very high pH values can sometimes negatively affect turf growth.

Golf Greens Topdress Criteria

  Sands without any gravel, silt, or clay are most desirable for topdressing sand based greens.  This will help to reduce the potential for layering and equipment damage.  A sand that is composed primarily of coarse and medium sand is preferred.  Guidelines such as the USGA particle size recommendations are often used to define the desired gradation of  these topdress sand.

  Native soil greens allow for a wider range of acceptable particle sizes than sand based, because of a lower risk of layering.   For these type of greens, sands ranging from fine to very coarse can be used for topdressing.  Minimal amounts of gravel, very coarse sand, very fine sand, silt, and clay are preferred.

Fairways & Sports Fields Topdress Criteria

  Selection of topdress sand for sand based fairways and sports fields allows for a coarser sand than for greens.  Very fine sand, silt, and clay should be kept to a minimum to aid drainage.  Small amounts of gravel and some very coarse sand, however, are acceptable due to higher cutting heights  and less fear of the potential for mower damage. 

  Topdressing sands for native soil fairways and sports fields have the widest range of acceptable particle sizes.  Once more, higher amounts of gravel and very coarse sand are acceptable.  Since a sand that will facilitate water movement is usually desired, high amounts of very fine sand, silt, and clay should again be avoided. 

  The extreme of topdressing is a process which is referred to as plating or capping.  Plating is used in cases where the existing soil will not support the desired level of turf grass.  Here we are attempting to provide a new soil by capping the existing soil with an imported material.  Capping materials can range in gradation requirements from a USGA sand (or similar) to a loamy soil.   For these situations it is sometimes acceptable to have high amounts of gravel or silt and clay.  The proper topdress for any given capping is often dependent upon the drainage design and available materials.

Final Thoughts

  Choosing an effective topdress sand requires knowledge of:

1. what outcome is desired from the topdressing program;

2. the physical properties of existing soil;

3. the physical properties of the proposed topdress.

  Turf Diagnostics & Design has the analytical tools needed to evaluate topdress materials.  Please contact us if we can help.

  Listed below are some very generic topdressing gradation guidelines.  They will not be appropriate for all projects, but may provide some guidance when selecting topdress sand. Desired topdress gradations for a specific program will vary depending upon the existing soil texture and specific project requirements. 

Send mail to turfdiag@turfdiag.com with questions or comments about this web site.
Copyright © 2005