Layering problems in a rootzone profile
should be aware that most sand sales in the UK are for other uses. The sports turf market is a small user in comparison. So be careful if you are offered cheap materials, as these are often finer, differ in shape, colour, lime content and are more interpacking than the sands specified for sports turf. Cheap top dressings are often comprised of sands with a wide range of particle sizes even when the amount of fine particles is small. When compressed they have a smaller total pore space than uniform sands and therefore inferior. For golf, winter pitches and bowling greens the dominant particle range in the sand should be medium sand (0.250 to 0.5mm) size range. For winter pitches, these would include fine sand for stability, which would not normally be necessary for golf and bowls. Increasingly, advisors are now specifying from 0.125 to 0.710mm size range for golf, though the main criteria for the reader is that the majority fall within the medium sand range. The mix should provide the correct balance of pore space and desired infiltration. Top dressings and
Incompatible top dressing on a uniform rootzone
rootzones should therefore comprise of a high proportion of sand in the mix, as this will assist with the control of aeration, infiltration, percolation and water retention. The next consideration is the very soil used in the top dressing, a point of major importance. Whilst sand supply in the UK is still reasonably plentiful, suitable topsoils are certainly not. With this point in mind we have a new breed of top dressings using lignite as the organic amendment. The lignite is sourced from our own quarry in Devon and has some unique properties other lignite’s and soils don’t possess:
1.Improved wetting
2.Excellent Nutrient Retention
3.Soil Conditioner 4.Consistency of supply 5.Long-term availability
If you would like more information, the product is called XL top dressing, with details on our web site, which is listed at the end of this article.
Taking core samples for top dressing compatibility 84
The best top soils for use in sports turf top dressings are
sandy soils, unless the top dressing is for use on cricket squares, when with few exceptions, we need clay contents in the range 27% to 33%. It has been long established that soils with clay contents less than about 24% have insufficient binding strength for cricket squares. The pH of top dressing is a poor guide to their likely effect on the rootzone pH. The most useful criterion is content of free lime (usually shell), which dissolves over time. A content of about 0.5% is the maximum advisable if you want to maintain an acidic rootzone. Obviously if you are trying to use a consistent top dressing formulation this is not possible if the supplier’s material is inconsistent. Therefore the supplier you use must have in place a quality control testing system to guarantee specifications and tolerances. Lack of quality control may be another reason for cheapness.
The 70:30 Myth
People who just ask for a 70:30 sand/soil mix in their top dressing (or any other ratio for that matter) don’t realise what lottery punters they are. This specification tells you nothing about the quality of the sand in terms of lime content, grading and conductivity, nor anything about the soil, which could range from peat-based to heavy clay content. A purchaser should be able
to request the precise analysis of the top dressing in terms of: particle size; amount of silt/clay; organic matter content and lime.
Feeling the heat
Another important point to mention is that any top dressing you buy should be heat-treated. If it’s too wet or damp then it tends to clog together or simply lies on the surface making an even application impossible. Not to mention the fact that if your top dressing is wet then you’re effectively paying your supplier for water!
Thatch and general organic matter control
For golf and bowling greens, the surface organic matter will accumulate in any fine turf when earthworms, the natural agents incorporating plant residues, are controlled. The rate of accumulation depends upon factors, which
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