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affect the rates of plant residue addition, and decomposition but a build-up cannot be prevented without both, active removal of plant residues by scarification and verticutting together with top dressing to ‘dilute’ organic matter at the surface. Top dressing should be applied whenever the surface has been disturbed, especially after verticutting/scarification, which prune turf and remove plant material, encourages new root development and tillering. The development of a significant and visually evident thatch must be avoided and it is much easier to avoid its development than to remove a thatch layer once developed. For soccer and rugby this is much less


of a problem because normally they do not have thatch problems due to wear and the reason for top dressing is to dilute fine soils which have been brought to the surface by earth worms. Most Soccer/Rugby pitches have an improved rootzone, which has been constructed on top of soil, and this finer material is taken to the surface by casting worms.


Application rates: Soccer and Rugby


We would advise 50 tonnes per year; this can be applied in one or two applications.


Golf and Bowling greens


Light frequent applications are always advisable throughout the growing season with annual rates varying from 2-8kg/m². Normally for maintenance the Greenkeeper would not use more than 6kg/m², higher rates per annum are being used on clay-based greens to increase the build up of surface rootzone. Single applications of around 3kg/m² or more are difficult to integrate with the rootzone and the Greenkeeper can lose turf condition if top dressings are over applied. It is much easier to integrate small amounts of top dressing and it has become common practice to apply four to six (sometimes more) top dressings of 0.5-1 kg/m² during the growing season.


The Testing Process Explained


Our whole testing process starts with a visit to the club. We usually take samples from three greens (a good one, poor and average) for golf greens and from various parts of a winter sports pitch. We use a core sampler, which takes a plug from the top 100mm of the profile. Other information is determined at the same time, for example the depth of the rootzone and thatch layer, any layering present and also the character of the soil or permeable material beneath the rootzone.


The samples are then sent to our in- house USGA PT accredited laboratory at Oakamoor in Staffordshire for analysis. Tests are carried out to determine particle size distribution, pH and organic matter content. We


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then take these results and feed them into our computer software. This in turn produces a full analysis that includes, amongst other elements:


Particle size distribution on full and half octave sieve sizes


D values which can be used to calculate the gradation index (D90/ D10) or used to ensure bridging characteristics with suitable gravels


Effective particle size (DK value) = the particle diameter that effectively represents the dominant influence on the hydraulic behaviour of a sand.


It can be used to predict: • Critical Tension


• Capillary Rise


• Pore-size compatibility with other materials


We can then use this information to identify a top dressing from our range that either matches a good rootzone or improves a poor one.


Summary


Top dressings are an integral part of sports turf maintenance. They serve several functions in sustaining turf quality. Furthermore they have been used successfully by many Greenkeepers and Groundsman to build up, over the years, a depth of high quality rootzone onto inferior material used in the original construction.


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