materials, to ensure that the best available are used, should be seen as a sound investment
Thatch problems on golf greens can also be experienced when pH levels are very acidic due to very low microbial activity. The pH of the rootzone mix will differ
from the pH of the rootzone sand as it will be influenced by the addition of the organic or inorganic amendment to the sand to form the rootzone. The ideal pH level for golf green grass
growth is 5.5 – 6.5 so this range should be targeted for the rootzone. A wider range of pH levels is acceptable for other sports pitches, for example football pitches that are growing a more pH tolerant species of grass.
C) SAND & GRAVEL - PARTICLE SHAPE
Moderate particle shapes are preferred for gravels, rootzone and topdressing sands. Sub-rounded to sub-angular particles with a medium degree of sphericity are ideal. However, a more angular shape is better for bunker sand to facilitate stacking on the bunker face and to reduce the chance of buried balls.
D) ORGANIC AND INORGANIC AMENDMENTS
The traditional organic amendments mixed with sand to form a rootzone are peat or soil. In recent years new organic amendments have been introduced to rootzones, for example green waste products & processed sewage sludge. The use of these ‘processed waste’ products is now widely encouraged as it is seen to be environmentally more acceptable. In the March 2004 revision of the USGA recommendations, inorganic amendments such as zeolites, diatomaceous earth and calcined clays are now considered acceptable for rootzone use. Peat can be tested for organic matter content, pH and fibre content to determine if it is a suitable organic amendment.
The suitability of soil for rootzone use can be determined from a soil texture analysis.
E) PREMIXED ROOTZONE - PHYSICAL PROPERTIES - USGA TEST
The use of suitable sand and a suitable amendment mixed together in the correct ratio will produce rootzone that is free draining while having the correct balance of air to water filled pore space to ensure that there is sufficient water retained for grass growth. The USGA test includes the PSD, particle shape, pH, organic matter
content, percolation rate, total porosity, air-filled porosity, water-filled porosity and water retention level at the relevant tension that corresponds to the depth of rootzone to be used in the construction.
F) USGA Design Test – 3 Recipe Set Test
Starting with the sand and amendment, the laboratory is able to determine the optimum mix ratio of sand to amendment in order to achieve the best balance of the physical properties in the rootzone mix.
G) GRAVEL COMPATIBILITY WITH ROOTZONE
Information derived from the particle size distribution analyses of rootzone and gravel materials is used to determine if the gravel is of a suitable size to ‘bridge’ with the rootzone and to ensure that ‘permeability’ will be maintained from the rootzone to the gravel layer below. This information is vital in order to
produce a profile where the gravel and rootzone layers sit cleanly on top of each other with no movement of rootzone into the gravel, whilst ensuring that adequate movement of water across the rootzone/gravel interface is maintained.
Guide to Test Sequence for New Constructions and Reconstructions
1.Source sand, rootzone, gravel and amendment materials that are available close to the project.
2.Have these tested for suitability by the laboratory.
3.Once suitable gravel is found it is advisable to check random deliveries to the site for quality control purposes.
4.If suitable premixed rootzone is found then random deliveries to site should also be tested for quality control purposes.
5.If the rootzone is to be mixed by the contractor when suitable sand and amendment materials have been located, have the laboratory determine the optimum mix ratio. The first bulk mix prepared should also be tested to determine that results correspond to the approved laboratory mix and then random subsequent mixes should be tested for quality control purposes.
TOPDRESSING MATERIALS
Light and frequent topdressing of sports pitches helps to produce level, firm surfaces and to dilute organic material as it forms at the surface. Materials used for topdressing should, where possible, have
a very similar particle size distribution, or preferably be identical to the material used in the construction in order to avoid layers of differing particle sizes forming at the surface. Using light dressings of the selected material frequently rather than heavy topdressing applications infrequently will also help in the avoidance of layer formation.
BUNKER SAND
Bunker sand should be tested for particle size distribution, pH, particle shape, percolation rate, crusting potential and penetrometer value. Particle size that is similar to that used in green construction is recommended as much bunker sand can be chipped onto adjacent greens. Extreme pH levels should be avoided as these can be detrimental to grass. Angular particle shapes are preferred for bunker sand to reduce the chance of buried balls and to help the sand stack against the bunker face. Bunker sand should drain at a rate in excess of 500 mm/hour.
The crusting potential in bunker sand is a check on the likelihood that the sand will form a crust at the surface when it dries out after wetting. Crusting is associated with high levels of silt and clay in the sand. Penetrometer value indicates if the sand has a tendency to bury balls or if the bunkers are likely to be excessively firm.
SELECTION OF TEST HOUSE
An accredited laboratory that specialises in testing for the sportsturf industry should be used if possible. USGA approves only the use of laboratories accredited to ISO 17025 through A2LA for testing to the USGA recommendations. Testing of the construction materials, to ensure that the best available are used, should be seen as a sound investment. When built and maintained properly golf greens and sports pitches can provide excellent playing surfaces over a period of many years.
Testing of the construction
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