If you were to poll 10 GSCAA superintendents about why they top-dress their playing surfaces, more than likely you will have a majority respond with, “I am trying to smooth out my surfaces”. But top-dressing can provide so much more.
According to turfgrass agronomist, Bob Wiley, “The principles behind top-dressing originate deep in the basic tenets of agriculture, and anyone who manages fine turf would do well to learn the real reason for the practice.”
Benefits to Top-Dressing with Gypsum
When a superintendent goes about deciding what materials to use when top-dressing he or she has to look at what the soils are like in the areas where the practice is occurring. If the soil history has good drainage, deep rooting, minimum compaction, the top-dressing materials should be of the same general nature, if available. If that material is not readily available or the soils are not good then an additional effort is needed. If the soils are not good and need to be changed overtime, additional methods may be required. So what are poor soils? Poor soils are generally defined as lacking soil structure, compacted; lacking nutrient availability, has very low or no microbial activity, inadequate surface or sub-surface drainage as well as a pH imbalance. I would first start out by having a reputable soils laboratory test your soil in order to determine what it lacks and what it needs. Once the testing has been finished and it has been determined what mix of soil, sand and organic matter is best for your program, then this becomes the permanent mixture for all future top-dressings and construction.
Once you have determined what mix you are going with I would strongly encourage you to “add” one additional product into your blend of materials. The additional component to your mixture would be pelletized gypsum. This final component is going to add a much needed punch to your already determined top-dressing. Gypsum is a relatively inexpensive material that can really make a huge difference in the health and playability of your surfaces. Not only does it provide a great source of calcium, gypsum will have amazing advantages such as:
- Reduces compaction and crusting in the top 6 inches of the soil profile. Along with the top-dressing mixture, gypsum, when worked into the soil profile it will flocculate the soil and create billions of tiny pockets. These pockets within the soil profile will cause a softening of the soil and thus become a natural aerator to complement your current cultural practices.
- Reduces disease and pest pressures. Gypsum is going to provide an excellent source of calcium to the plant. While calcium is considered a secondary nutrient, it may provide the best protection against disease and pest pressures. Calcium, when soluble is absorbed into the plant cell wall making a very strong up-right standing plant. When plant cell walls are strong and healthy, disease and pest pressures are reduced greatly.
- Increases water infiltration as well as the water holding capacity of the plant. When gypsum is applied to the surface, as discussed earlier it flocculates the soil profile. Once this occurs the crusting on the surface is eliminated and the compaction layers are greatly reduced. When this occurs, excess water is free to flow through the profile and back into the sub-soil regions; this will greatly reduce ponding or standing water after heavy rains or extended irrigation cycles. It is also going to allow for water to become “trapped” within those billions of tiny pockets to act as a reservoir for the plants, which will in turn reduce your needs for running your irrigation systems. There have been documented cases at golf courses where their water use has been reduced by nearly 40%. As you can imagine, when the dog days of summer have hit, your turf will stay greener, and more lush because of the pockets created by the gypsum use.
- Gypsum will remediate high sodium soils. Calcium is a divalent (double positive charge), and the atomic weight of the calcium molecule being 40 and the sodium molecule being 23 with a single charge, sodium can be replaced in the soil colloid by calcium. The sodium is then ionized in the soil solution, which can then be flushed out of the root zone into the sub-soil where it can’t harm the plant anymore.
How much and How Often to Top-Dress
With the technology that is available to the superintendent today, it is recommended that you top-dress lightly but frequently to maximize your desired results. Depending on the size of the surface that you are top-dressing 4-5 times per year should be adequate. Be sure to space them evenly throughout the year so the materials have an opportunity to sift into the turf and mingle with the grasses in order to carry out its valuable functions. When determining how much gypsum to apply with the top-dressing mix, it depends on the size of pelletized gypsum you are using, but a good rule of thumb is to go with 20-40 lbs per 1000 sq. ft. So if your average green is 5000 sq ft you can plan on blending 100-200 pounds per green into your top-dressing mix, this will equate to about 1 ½ tons for all 18 greens and your practice green.
Aerification
Aerification is a very important cultural practice in order to maintain a healthy playing surface. Typically, when the aerification process takes place, it is done for several reasons; compaction relief, water infiltration, transfer of gasses, removing poor soil profiles, increases the potential for deeper thicker rooting. While aerification is a necessary practice there is the potential for the number of times aerification is needed to be reduced. Spring Valley Golf Course in Livermore, Iowa hasn’t aerified their playing surfaces in over 5 years because there is not a need to do so. According the their long time superintendent Curt Bertie, “ Spring Valley has fast, receptive greens that are not compacted, with roots that grow well past the depth of the cup and with very little thatch.”
Summary
The process of top-dressing is a common practice among golf courses throughout the world. However, adding the additional material of gypsum is not as common. As discussed throughout this article, gypsum will enhance your current top-dressing practice by providing beneficial nutrients and scientifically proven results to maintain a healthy, lush playing surface. Gypsum is not going to provide immediate, noticeable results, over time not only will you see noticeable changes to your soils profile but your customers (the golfer’s) will begin to notice a far superior playing surface. Gypsum will provide conditions that promote faster greens with less thatch, more receptive to shots that are coming into the playing surface as well as less disruption of play due to aerification or vertical cutting of the greens. The long range benefits are undeniable! Next time you top-dress, add in gypsum, give it a chance and see the difference.
Note: Be sure that when you choose your gypsum source; make sure the purity is 92% or better and that you are using a dihydrite form of gypsum. This form is extremely water soluble and will begin to work immediately.
I want to give a special thanks to the USGA Greens Record for providing some information in this blog.
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