Choosing the right sand can be a huge decision. Graeme King, Managing Director of leading sports sands supplier Hugh King & Co, reveals some of the key factors to consider.
Sand can play a defining role in the creation of high performance sports turf. It can encourage fine grasses, which are generally more desirable. It can improve shoot density, which enhances the quality of the sward, and it can dilute organic content in the surface layer, helping to firm up the green.
Applying the right sand can mean the difference between building up a surface resembling a patchwork of colours and textures, and one that is consistently firm and smooth. It can mean pitches, greens and bunkers drain in wet weather rather than becoming clogged and choked. Choosing the right sand can be one of the most important decisions you make.
The first step to choosing the right sand is to identify the composition of the existing, indigenous sand. This will provide the basis on which your sand selection will be made. To properly identify the characteristics of this sand, a sample needs to be analysed and the different particle sizes contained within the sample categorised. This is achieved by passing the sand through a series of sieves.
Quality suppliers will have their own laboratory facilities. This resource means they can test their products for consistency and composition, and help clients to identify the features of their own sand.
Understandably, very few sporting venues have their own on-site laboratories and many will call on the services of a reputable soil testing establishment for quality and performance testing. The in-depth data and analysis that is provided confirms different performance characteristics and can underpin ongoing and future maintenance programmes.
For sand, this information manifests itself in three forms, with the most important being particle size distribution. This essentially shows the range of particle sizes (in percentages) found within a given sample and, therefore, determines the sand's classification - coarse, medium or fine. This data is key, because the amount of particles in relation to the size of the particle will determine how the sand performs in different situations.
The second information source relates to percolation rates, i.e. how fast water drains through the sand. This is done by first saturating the sample - the amount of water that enters the sand during a predetermined period (usually an hour) is called the infiltration rate. Different sand types will have different infiltration rates, which are determined by their texture and structure. This, in turn, will affect how quickly water percolates through the sand, which is measured in inches or millimetres per hour.
Since dry materials absorb water more quickly than wet ones, the infiltration rate is measured after the soil has been saturated. The percolation rate for a sandy soil is approximately 30mm per hour.
The third crucial test is assessing the relative pH value of the sand. This is a measure of acidity and alkalinity using a scale from one to fourteen; where seven is neutral; less than seven is acidic, and greater than seven is alkaline. It is worthwhile pointing out that pH is a logarithmic scale, so the difference between a pH of 7 and a pH of 6 is 10 times the acidity, between 7 and 5 is a 100 times the acidity and, between 7 and 4, is a 1,000 times the acidity. This clearly has an influence on how grasses will grow and, as such, is a key indicator to consider.
Armed with a proper assessment of your own sand, it is now time to source a non-native sand that will complement and/or improve the conditioning of your turf. As ever, this may not be as straightforward as it first sounds.
There are many different types of sand available, each with different characteristics, and each performing a different function. But, as we have found out, the science of sand is carried out at an almost microscopic level, where the geography of individual particles determines the qualities of the products. With this in mind, there are three main areas for consideration - particle size, particle shape and particle colour.
Let us begin with particle size. In the world of sand, particle size has a huge impact on the draining characteristics of your turf. The larger the particle size, the more free draining the sand will be.
In many circumstances, the apparent choice would be to opt for a sand with the largest particle size but, sadly, this could be a costly mistake. Firstly, particles that are over 1mm in diameter can be an aesthetic nuisance showing up on the surface of a green. More concerning is the fact that particles at this size can also cause damage to mowers during cutting, which leads to the prospect of kit being out of use and the likelihood of hefty repair bills.
Going large is perhaps not the best option. Unfortunately, going small can be equally devastating. If we take a typical concrete sand, we will find a medium containing plenty of coarse particles, but also a fair proportion of fine particles at the silt/clay level. These finer particles can often bond together causing a capping affect which prevents water draining properly.
This problem is prevalent in golf courses when clubs use their own sand excavated from an on-site quarry. Whilst the particle size may be perfectly suitable, the natural silty/clay fraction can affect drainage. An example of this would be a bunker that has drained perfectly well for a number of years, then suddenly starts to puddle. Worse still if this happens on the fairways or greens.
An ideal compromise is a single-sized sand, with virtually nothing in the very fine category. This will allow the sand to drain consistently and is an ideal candidate for sites where drainage is an issue, for instance, inland golf courses.
But, of course, it doesn't all come down to size. The shape of the sand particles can also play a part in drainage. Brown sand, for instance, is wind blown from the sea or riverbeds and, as a result, has a rounded particle shape. This profile means there is always route ways between the particles, no matter how tightly they are squeezed together (imagine a large basket full of footballs). These canals make brown sand ideal for applications where drainage is important.
Whilst brown sand benefits from a secure network of arteries, white sand particles are angular in shape and naturally bed together like a stack of triangles. Closer knit, the pointed shape of these particles means white sand does not drain as freely as a round-grained sand. Moreover, because white sand is formed by crushing sandstone rock, which is soft in nature, the particles are often held together with clay, which needs to be removed through a series of intense washing cycles.
The material differences between brown and white sand have an obvious influence over drainage, but the physical inconsistencies don't stop there. More obvious than discrepancies in particle shape is the clear mismatch in colour, which is determined by the level of iron oxide in the sand - brown sand has approximately 1.5-2.5% iron whilst white has less than 0.3%.
That said, colour is really only important from the aesthetic point of view. Most golf courses, for example, look to blend sand into the landscape, so often choose the light-brown option because of its natural appearance. Although inland courses find white or brown agreeable, with the former giving them a pleasant contrast, white sand has developed something of a reputation, which some find disconcerting.
This disrepute is founded on the idea that white sand reflects sunlight and can, therefore, burn the grass. Its angular shape is also charged with nipping at the grass. The truth is, white sand has a number of admirable qualities, particularly in bunkers, where the larger particles and clusters of particles keep the sand in the bunker rather than blowing across the course.
Despite these virtues, there are some who would find it difficult to tolerate white sand, particularly on links courses. The tradition of maintaining a natural look often precludes the use of white sand, despite its characteristics being well suited for the extreme weather conditions found on these courses. It would appear that brown is the only option.
Happily, this isn't the case. Combining brown and white sand in a special blend offers the best of both worlds - the drainage capabilities and natural look of brown sand, joined by the 'stayability' of white. This apparent match made in heaven satisfies a number of requirements and would seem to be the perfect solution, if it wasn't for a small caveat.
Whilst the two sands possess different qualities separately, and an alluring mix when combined, the method of uniting the sands will dictate the potency of the blend. For instance, combining two stockpiles of sand using a loading shovel will only create a segregated mixture that is inconsistent and unpredictable. Once applied to a green, for instance, these irregularities will promote variances in drainage. Areas with too much white sand will retain water, whilst areas dominated by brown will drain more quickly. Instead of a uniform playing surface, you will have a patchwork quilt of growth and decline.
Reassuringly, sand blends produced at industrial sites are created using production processes that begin with white rock being crushed and brown sand being added via a separate feed hopper. The two sands are washed together and slowly become one as they pass through a series of processes designed to produce a consistent end result.
Whether you opt for a brown sand, a white sand, or a combination of the two, it is important to recognise the significance of this decision. After all, sand is the lifeblood of sports turfs. It can encourage fine grasses, improve the quality of the sward and dilute organic content. The apparently simple act of applying it can do so much.
But, selecting the right sand is an involved process. It rests upon properly identifying the composition of your own sand, and then matching it to an appropriate sand product. Size, shape and colour all have their part to play, as does the condition of the turf and your ambitions for it.
Sand can play a central role in producing high-quality turf, so choose wisely.
Based in Ayrshire, Hugh King & Co has been supplying sand for over 150 years. The family owned company is run by Graeme King and supplies over 100 golf courses with high-quality sand for topdressing, bunkers and soil amelioration. It also supplies sand to a variety of winter sports pitches. For more information, please visit www.golf.hughking.co.uk