Golf Greens Top-Dressing

Top-dressing is an important activity which should not be neglected, with a sandy, with organic elements, material being ideal. Various top-dressing periods can be considered, from traditional spring and early autumn applications, to regular very light dressings during the playing season at monthly intervals. The shorter the routine cut of the greens the more frequent the application of top-dressing, but tis will also depend on the intensity and amount of play that takes place. For greens cut at 5mm for most of the year two applications as a minimum might be typical, for 4mm cut greens this might be a minimum of 3 applications (April, June and September), whilst for very short cut green 3-3.5mm this might be monthly to fortnightly, which essentially is a light dusting.

For greens cut at 4 to 5mm another option is for a light monthly ‘dusting’ of about 0.5 kg/m² to be given from March, if mild temperatures are present, through to at least June to maintain surface smoothness, if over winter use has not impacted excessively on surface evenness. The actual top-dressing programme which is undertaken should be matched to meet the needs of the particular greens on the course, but the above comments provide a good indication of some typical variabilities.

Many top-dressings are of a purely mineral nature, without having been created from traditional compost heaps with added farmyard manure, leaf mould or seaweed, which has decomposed to become an integral part of the soil. The nutrients and micro-organisms which were previously added to greens from the use of these types of top-dressings was considerable and would have contributed in maintaining or improving soil health, and would act to counter the negative effects of pesticide application to a green.

Where pure sand top-dressings are applied on a routine and almost continuous basis then this practice can more readily contribute to the development of Dry Patch. Changing top-dressing composition on a regular basis is not recommended as this can lead to layering and root breaks within the rootzone profile. Inadequate preparation, from activities such as aeration and scarification, prior to the application of a top-dressing will also contribute to layering. Good preparation work is required to assist in a more uniform incorporation of the top-dressing into the rootzone profile. Regular light dustings of top-dressing throughout the growing season might help maintain very smooth playing surfaces, especially on those greens which are cut very short, but it is can often be difficult to carry out much scarification or aeration prior to this type of application without causing even minor surface disturbance which sort of negates the purpose of regular light applications.

The careful working in of a top-dressing is more critical on a golf green than any other playing surface. This is due to the size of the golf ball and the influence even very minor surface irregularities can have on the roll of a ball. Dragbrushing, dragmatting or luting of any top-dressing into the sward should be carried out at a controlled, uniform and steady pace and certainly not too fast because the equipment can easily bounce and ‘bobble’ along the surface causing minor wavy micro-ridges to develop.

Top-dressings are often quoted as being 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:
o Clay: 1%-3%.
o Silt: 1%-3%.
o Very fine sand: 2%-5%.
o Maximum total for Clay, Silt & Very Fine Sand: 10%.
o Minimum for Clay, Silt & Very Fine Sand: 5%.
o Fine Sand: 10%-20%.
o Medium Sand: 70%-90%.
o Coarse Sand: 10%-20%.
o Very Coarse Sand: 0% - 2%.
o Organic matter content: 2% - 5%.
o Hydraulic conductivity (water percolation rate): 150-350mm/hr.
o Total porosity: >35%.
(adapted from 1. Baker, S. (2006) ‘Rootzones, sands and top-dressing materials for sports turf’, STRI; 2. Arthur, J. (2003) ‘Practical Greenkeeping’, P.85)

The organic, humus, content should not be sourced from sphagnum moss as this can be very difficult to rewet once dried, even with the use of wetting agents. (Arthur, J. (2003) ‘Practical Greenkeeping’, P.87)