The battle of the bunkers
I'm convinced that the colorful language that emits from golfers' mouths originated from players trying to extricate golf shots from the sand burrows that grazing sheep created in the sand on the old course at St. Andrews. Although sand bunkers have changed dramatically since that time, the language and frustration of the average golfer faced with a bunker shot remains pretty much the same. Not surprisingly, golfers complain more about bunkers--too soft, too hard, too wet, too dry--than anything else on the golf course. Nevertheless, according to the Rules of Golf, some penalty should exist for poorly hit shots--it's part of the game. Thus, bunkers have a profound influence on the character of a course and play a strategic role in the architect's design.
Bunker maintenance will always be a formidable, but unavoidable, part of the golf-course superintendent's job. However, consistently following good maintenance practices will provide good playing conditions and cut back on complaints and any resulting negative perception the golfer may have of the course. In addition, it can extend the useful life of your bunker sand, delaying costly replacement.
Start with the right material Using good sand is a "must" and can prevent numerous maintenance nightmares. This means using USGA-standard particle size and shape. The best particle sizes for bunker sands are confined to a relatively narrow particle-size range. The majority of the particles in the sand you use should be between the 0.25 and 1.00 mm wide. Other factors to consider are particle shape, color and cost. Generally, the best bunker sands are quartz-based and angular in shape to provide reasonable firmness.
Angular sands have flat sides, which interlock with those of other particles to establish stability. This is important because it provides firm footing for a good golf swing. Angular sands also better resist excessive washing from bunker slopes (due to irrigation or rain) and they minimize "fried-egg" lies.
You can perform in-house testing to evaluate and compare sand angularity or sharpness. One method involves using a pocket penetrometer and recording how much pressure you must apply to press a golf ball into moist sand samples set up in a box. Another is to use oven-dry sand and measure the angle of repose. Pile the material to the highest angle possible without the grains beginning to avalanche down the side of the pile. The more angular the particle, the greater the angle of repose it can achieve. In other words, greater angularity allows you to pile the sand more steeply before it starts to slide downward.
Color should be secondary in importance and has more to do with aesthetics than function. That is not to say that color is irrelevant. White sands create more maintenance problems because they show contamination much more readily. However, there's no denying that white sands are beautiful. They show up well and create a wonderful visual scene for the golfer. Nevertheless, particle shape and cost are of much greater importance from a maintenance standpoint. A word of caution: Some sands that technically fall within USGA guidelines still may not be suitable or acceptable to some or all of the members of your club. Test sands available in your area with your members.
To maintain good playing conditions in bunkers, superintendents must rake, edge, control weeds and see that all bunkers drain properly. In addition, superintendents must cut down on cost by extending the life of bunker sands by reducing contamination. The rest of this article will cover methods of performing these tasks.
Contamination prevention >From the moment you add new sand to a bunker, contamination occurs, shortening the sand's remaining useful life. Because contamination is the most significant factor leading to costly renovation of sand bunkers, you should perform all bunker maintenance in ways that minimize contamination. Improper maintenance allows silt, clay and organic matter to accumulate in the sand. These fine particles gradually fill in pore spaces between the sand particles and cause poor drainage, discoloration and allow the material to become hard and crusted.
You can slow this "aging" of sand bunkers with proper maintenance. Good maintenance practices will increase the useful life of bunker sands and significantly lower expenses by delaying costly bunker renovations. More importantly, you can achieve good playing conditions by practicing proper raking, edging and weed control and by assuring that bunkers drain well. Ultimately, playing conditions take precedence over other maintenance considerations.
Raking Before the 1960s, raking was a laborious, time-consuming, costly operation. The advent of the power rake has reduced this cost. Unfortunately, superintendents often assign the task of raking bunkers to a new or less-proficient employee. This can be false economy. Correct and careful raking prevents the need for costly additions of sand and premature renovation. Further, because raking bunkers is one of the most frequently performed maintenance practices, it has the potential--if done improperly--to cause the most problems and complaints. After a bunker is raked, it should give the golfer a fair lie. If it doesn't, you're sure to hear about it.
* Hand Raking. Unfortunately, not many superintendents have the budget to hand-rake bunkers. However, there's no doubt that hand raking is the ideal method to ensure a fair lie. It also has several other distinct advantages. Hand raking offers the opportunity for a trained employee to check bunker depth on the floor and slopes. In addition, it minimizes mixing of organic matter, such as leaves and clippings, into the sand, cutting down on contamination. The greatest benefit of hand raking is uniformity. Golfers want and expect to be able to play sand shots out of sand that is consistently firm and uniform throughout the course.
Preferences of surface characteristics vary from golfer to golfer. Two golfers in a foursome may prefer a smooth surface while the other two prefer furrows, so you can't please everyone. The surface characteristics you create can vary from smooth to distinctly grooved or furrowed and depend on the raking procedure and type of rake you use. Remember that it's more important to be consistent than to have any one particular type of surface.
You can use any method of hand raking as long as you exercise care that you don't leave ridges of sand at the termination of either the backward or forward stroke. Do not get in a hurry as this could leave waves in the sand. Give careful attention to raking the perimeters of bunkers. Rake the sand on the fairway side of the bunker, or backside, so that the sand is level with the turf. This will ease difficult lies.
* Power raking. Since the introduction of power sand rakes, bunker raking is not as laborious and costly as it once was. But if you factor in lower bunker quality, increased aging of sand and the cost of the machines, the savings are not as great as they first appear. With that said, the power rake obviously is here to stay and, if you use it properly, it is an invaluable maintenance tool.
As I noted previously, putting new or less-proficient employees on power sand rakes can be a false economy. Correct and careful raking of each bunker is important: The bunker-rake operator should be one of the best-trained employees and should be rewarded as such.
Bunker-rake cultivation tools include a wide range of implements from which to choose. Different sand types and ages require different cultivation tools. Shop around and you will find the best for your sand bunkers.
Drive mechanical bunker rakes into a bunker and then lower the cultivation tools. Drive slowly around the bunker in a circular or figure-eight pattern. Do not create waves or deep furrows. Keep power rakes 18 to 24 inches away from bunker edges and off of slopes (see photo, page G 44). Also, stay out of deep bays. Improper use of mechanical bunker rakes or having the wrong cultivation tools can lead to mixing of sand and soil. This occurs when the machine gets too close to the edge of the bunker or the cultivation tools are too deep for sand.
Lift cultivation tools or rakes before exiting the bunker and always enter and exit at different points. The operator should smooth up the exit point by hand raking. Most importantly, rake and smooth all edges by raking sand back toward the edges. Greenside bunkers should have at least a 2-inch lip to prevent the use of a putter for bunker shots. You always should carry a manual sand rake on the machine for the hand raking that you'll need to complete the job you begin with a power rake.
It is critical that you monitor sand depth closely if you use mechanical rakes. Bunkers should have at least 4 to 6 inches of sand on the bottom. Do not let raking shift the sand around; this means that it will be too thin in some areas.
Edging Grass encroachment into bunkers is a continual problem. Therefore, to maintain the original shape, you must edge bunkers. Edging frequently with string trimmers or reciprocating or mechanical edgers will minimize the need for more severe edging. During favorable growing conditions, edging may be necessary every 2 weeks.
If you do not edge the grass periodically, the turf will grow inward, reducing the size and obscuring the shape of the bunker. Some bunker edges have been known to grow inward several feet, and the original perimeter could only be found by digging or probing. Frequent edging should prevent this problem. If you need to perform more severe edging to reestablish the original edge, rake back the sand and use straight-blade hand shovels. Then be sure to remove all debris.
You can achieve a relatively natural look by using a spin trimmer and allowing grass to grow on the bunker face down to the level of the sand. Another approach is to use a mechanical edger or reciprocating trimmer (see photo, page G 48). This can leave a "cutter" effect with no turf growing on the bunker face. A reminder here--sand and turf should meet on the back side, so the cutter effect is not what you want there.
During all edging procedures, remember not to contaminate the sand any more than necessary. This also includes mowing around bunkers. Use caution to keep from blowing large volumes of clippings into the sand: clippings add to the aging process of the sand.
You can reduce edging somewhat by using plant growth regulators (PGRs). Not all PGRs affect lateral growth of turfgrass. Thus, some may not actually reduce the frequency of edging. However, even when this is the case, reduced mowing frequency decreases clipping contamination.
In addition, you may want to consider using some of the fine-textured zoysias that are now available. Their slower growth cuts down on encroachment into bunkers and they blend in well with bermudagrass.
Sand washing Washing is without a doubt the single largest source of sand contamination, and throwing sand back on bunker faces after heavy rains is one of the most costly and labor-intensive tasks you'll face.
Preventive maintenance will help reduce this cost. The way to minimize the impact of washouts is with good drainage; not only in the bottom of the bunker but also at the top of the slope, where a "smile" drain can be of benefit. Also, see that water does not enter the top of the bunker--use a swale to divert water or install interceptor drains to carry off surface runoff.
Architectural designs that use steep slopes or flashing cause the most maintenance problems. A good way to minimize the impact of washouts on bunkers with such designs is to construct a deep vertical lip along the top edge of the bunker. This vertical lip then leads down to a flat surface at a 90-degree angle. You then pack the cut with sand (see figure, above). With this design, water drains straight down through the deep sand instead of hitting the steep clay slope and washing out, taking sand with it. The disadvantage of this procedure is the amount of sand needed and the possibility of "fried-egg" lies.
In most areas of the country, good subsurface drainage is a must for bunkers. A superintendent should perform any maintenance or preventive practice possible to increase drainage to prevent washouts and contamination.
Other maintenance practices Greenside bunkers that receive a lot of play can have a substantial build up of sand over time. You should monitor this and return the sand to its original elevation and distribution. Wind also can have the same effect. In winter, some superintendents erect snow fences to prevent sand from blowing. If wind is a factor at your location, use sand at the high end of particle-size range to reduce blowing.
Liners A good way to eliminate or greatly diminish soil contamination is with the use of geotextile liners, and there is no doubt that liners perform this function well. Plus, liners eliminate discoloration from underlying red clay and resist rocks that gravitate to the surface and contaminate the sand. However, many courses have installed liners only to remove them later. Liners make it difficult to keep sand at a uniform depth, and mechanical rakes tend to snag the fabric. Of course, if you are hand raking bunkers, this is not a problem (yet another argument for hand raking!).
New technology The latest technology for preventing contamination and lowering maintenance costs is a bunker stabilizer that is blown in as you would Gunite (see photo, page G 48). You line bunkers with a 2-inch layer of this material and allow it to dry before adding sand. The material remains resilient but eliminates mixing of soil and sand. Because this technology is new, it's long-term value and durability remain to be seen. But it is certainly intriguing at this point. On steep faces, this material allows you to place as little as 1 to 2 inches of sand. The ball does not "plug" and rolls toward the bottom of the bunker after impact.
By using good maintenance practices and being conscious of contamination, you can lengthen the life of bunker sands and diminish maintenance costs. You also can enjoy your trips to the pro shop to interact with golfers who have just finished a round of golf on smooth, well-maintained and uniform bunkers.
Wallace "Tinker" Clift, C.G.C.S., is department chair of the golf-course and turfgrass management program at Texas State Technical College (Waco, Texas).
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