Technical
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,
“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”
FEBRUARY/MARCH 2012 PC 113
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