Bowling Green Top-dressing

Top-dressing is an important activity which should not be neglected, but due to the cost it can sometimes easily be ignored or delayed by clubs for another year in the hope that saving money will not affect playing quality too much. This can be a false economy and the bowling green will gradually deteriorate if regular top-dressings are not carried out.

Top-dressing might be carried out for a number of reasons, such as to dilute thatch depth, maintain openness of hollow-cored areas, improve surface evenness and improve surface levels by gradual smoothing out of depressions.

To identify high or low spots on a green, place a taught string from one end to another and this will help to show up the depth of any depressions. The edges of greens are also prone to sinking away towards the ditch due to this being the main place players access greens and where machines, especially mowers, turn on a regular basis. Place a 3-m straight edge on a level part of the green to extend it over the edge to help to indicate the extent of any drop; this could then either be lifted by cutting back the turf and raising up by importing the required quantity of rootzone and then relaying existing turf or using new imported turf, although if the latter there will most likely be a distinct different in sward appearance with the rest of the green. A gradual approach to addressing unevenness might also be attempted by undertaking regular top-dressings during the playing season, and continuing with this over several years.

Watch out for heavy downpours of rain as seeing where water collects can also help to readily identify low spots. Take pictures of these and they can then be more easily located and then worked on when carrying out selected top-dressing to help raise up these slight depressions.

If the soil within the green is suitable, and where compaction or thatch is a problem, it might be worth considering hollow tining to extract soil cores onto the surface and then break them down with a metal drag mat, or light scarification, or similar, and work them back into the created hollow-tine holes along with just a small amount of additional topdressing, say 2-3 tonnes. Any extracted thatch will typically be separated from any soil cores during this breaking down activity and can be removed by using a cylinder mower with the height of cut set relatively high, about 10mm. A second hand or reserve mower is usually good for this type of activity as any slight damage or wear to a bottom blade / cylinder from any coarse material which has been removed by a hollow tine will not be a particular problem. The use of a rotary mower (blade set high), sweeper or leaf blower might also be considered to help clean the surface of debris.

A sandy loam is typically applied, but the exact percentage of sand will vary slightly according to requirements and the composition of the original rootzone. Where a sandy rootzone already exists, it is usually a good idea to top-dress with similar material.
The purpose of this is to ensure that a distinct layer or capillary break does not occur as this would be detrimental to the roots and sward. Bowls is played over the, often, drier summer months, in contrast to golf greens which are year-round play. A slightly higher percentage of fines (particles less than 0.125mm) can be permitted, and may even be more beneficial, for bowling green situations in contrast to golf greens.

Top-dressings are often quoted as being 60:40; 70:30, or 80:20. What this means, for example, is that for an 80:20 soil, 80% of the finished product mixture is from a sand whilst 20% is from a sandy soil. Technically it is not a helpful term as it doesn’t give any indication of the different particle size ranges which might be present, but as a general guide it is suitable to quote such figures in conversation, but not for when purchasing materials. In this latter case, it is essential to confirm the particle size analysis of the product to ensure the material isn’t an 80% builders’ sand with 20% clay.

As a general guide the following specification can be used for adapting to the needs of an individual green:
• Clay & Silt: 0.5%-5%.
• Very fine sand: 5%-20%.
• Maximum total for Clay, Silt & Very Fine Sand: 20%.
• Minimum for Clay, Silt & Very Fine Sand: 8%.
• Fine Sand: 10%-20%.
• Medium Sand: 60%-80%.
• Coarse Sand: 5%-25%.
• Very Coarse Sand: 0% - 2%.
• Organic matter content: 1% - 4%.
• Hydraulic conductivity (water percolation rate): 100-250mm/hr.
• Total porosity: >35%.
(adapted from Baker, S. (2006) ‘Rootzones, sands and top-dressing materials for sports turf’, STRI)

A light spring topdressing might be from 1 - 1.5kg/m² (1.5 - 2.25-tonnes a green) up to 2.5kg/m² (3.75-tonnes) where damage has occurred over the winter, or where the autumn renovation work was not as successful as would be desired. Making sure any spring top-dressing material is well screened and does not contain any coarse material is essential because the potential for the scratching of woods from gritty particles can arise if the top-dressing is applied late or not worked in adequately.

End of season renovation will vary depending upon resources and condition of the green, but with different tines the following might be a useful guide:
• slit-tining it might 1.5-2kg/m² (2.25 -3 tonnes).
• with solid tining at close spacing the application rate might be 2.5- 3kg/m² (3.75 - 4.5-tonnes).
• whilst with hollow-tining it might be in the region of 3.5 - 5 kg/m² (5.25 - 7.5 tonnes), although this would probably be best applied as two applications at half rates to help incorporation into the holes produced by the tining activity.

It is unlikely that more than about 7 kg/m² (10 tonnes) would be used in any top-dressing operation, but the closer and deeper the hollow-tining, along with diameter of the tine, the more material would be needed for soil replacement activities.

A general autumn top-dressing of 5-6 tons of a sharp sand or sandy soil might have been typical in the 1950s and 1960s. (Greenfield, I. (1962), ‘Turf Culture’, p.207)
Be careful not to top-dress too heavily late in the year because the top-dressing will provide an increased level of relative humidity around the grass leaves and this will increase the probability of an attack of Fusarium patch disease.

If it is possible to carry out renovation of a bowling green during early September, which will also typically be when major competitions will have been completed by, then this work can usually be carried out relatively quickly – hollow-tining, clearing up of cores, top-dressing, seeding and working in can usually be accomplished in 2-days with adequate workers.

The benefit of this approach is that the weather will be drier than at the end of the month to early October which will significantly speed up application and incorporation of any top-dressings. Hollow-tine cores will be lighter than when wetter and easier to clean up and grass seed will more rapidly germinate and establish because soil temperatures are close to optimal. Play will be able to continue after the works and with the games mostly being casual or general club competition this should be an acceptable compromise in helping to ensure solid foundations for improved bowling green conditions for the subsequent year. If the correct top-dressing has been used there shouldn’t be gritty coarse sand so players bowls should not be scratched, which can be a concern. Play may not be as good as before the works, but the slight drop in pace / draw should be of minor concern when compared with the benefits accrued to the overall condition of the green. Make the most of nature’s ‘windows of opportunity’ to help the green and make best use of often limited resources.

During the playing season regular monthly, light applications (dustings) of about 0.5 kg/m² (0.75 tonne) might also be considered following the use of a spiked roller (e.g. a Sarel).

The range of permutations for top-dressing requirements is quite varied, so each club will need to consider what is best for their particular needs.