HOW LOW should you go?
In part 1 of a new series Ian Howard, MD of Dennis Mowers, offers advice on bowling green maintenance. Part 1: Is height of cut debate the key to faster greens?
It seems that cutting height is not a panacea for fast play on bowling greens. Greenkeepers with a need for speed should instead focus on regular, and gentle, thatch removal. Height of cut is believed, by
many, to be key to the performance of bowling greens - the shorter the cut the faster the play. But mower manufacturer Dennis, as well as other leading industry figures, says that you can have speed without cutting below 5mm, although many continue to do so as they say it is easier than verti-cutting and scarifying. “Most bowling greenkeepers
have experienced slow greens during mid season,” says Dennis MD Ian Howard. “And, in every club, there are as many advisors on the green, and how to speed up play, as there are members. All are eager to share their ‘superior knowledge’ on green keeping with the person actually doing the job, but who’s right?” The traditional way to prevent that mid-season lull is to rip out the thatch with a scarifier - either hired, borrowed or owned - at the end of the season. “But the green often takes most of the closed season to recover,” says Ian.
“Scarifying to a depth of 15 to 30mm inevitably removes a massive amount of thatch. Reports of hundreds of bin bags of debris being removed are not uncommon with this method and, while there is a degree of satisfaction at having given the green a ‘really good going over’, the benefits of the exercise are short lived”. The process inevitably damages the grass roots and the plants themselves and they are then expected to recover in the off season when light levels are at their lowest. “Damp, rain and disease creep in at this time too and, if the plants are vulnerable, due to excessive disturbance or damage, they are more likely to suffer problems.” This winter setback is then compounded at the start of the season when the cutting height is often immediately reduced to 6mm. The thatch layer, inevitably, builds up in the spring and, by June, bowlers
begin to complain that greens have slowed from their fast pace at the beginning of the season. “So then there’s pressure on the greenkeeper to reduce grass height - to 5mm, 4mm and eventually 3mm - to improve the speed of play” says Ian. “Thatch thrives in these conditions and the grass plants required to give the upright mat becomes severely stressed as leaf area is their lifeblood. All nutrient production and absorption depends on the photosynthesis process and if leaf area is reduced then it’s limited.
“Changing from 4mm to 3mm cutting heights reduces the leaf area by 25% and, consequently the desirable species do not thrive” he adds.
Thatch then dominates and
allows moss and diseases to take hold. The plant base becomes choked with thatch, which stunts the grass of water, air and applied nutrients. And, the more the thatch takes hold, the slower the green becomes. “The cycle continues on its
downward spiral - bowlers call for lower clip height in a bid to speed up play and the cycle of poor plant health continues.” “At this stage the green becomes very vulnerable to drought and irrigation, or any rain that does fall, fails to reach the roots as it’s bound up in the thatch layer. From here it evaporates in the breeze and sunshine” explains Ian. The colour of the green also
suffers. “Brown patchy areas look ugly and there is the temptation to spread feed onto the
surface to try to improve things. But, the grass roots find it very difficult to absorb this feed due to it being bound up in the thatch and any that does reach the roots cannot be efficiently turned into growth as the leaf area of the plant is now so small it is hardly functional. The only thing that thrives is the thatch itself!”
Ian advocates a switch to modern thinking and methods. Since the development of Dennis FT cassette system, bowling club greenkeepers have been at the centre of a self- created revolution. The ability to regularly verti- cut or light scarify greens with a machine fitted with a rear roller has meant that play is not affected. Monthly, fortnightly or weekly treatment, depending on the conditions, helps to prevent the build up of a thatch layer by constantly cleaning around the plant and removing the diseased, dying or dead matter, as well as controlling horizontal grass growth. “Every green has horizontal
growth and always will - the prospect of eliminating it is impossible” says Ian. Annual meadow grass (poa annua) is another problem that can slow down play. “Regular verti-cutting helps control the density of this species but, like horizontal growths, it is difficult to eliminate completely as birds and wind readily deposit seed back on to greens.” He adds that regular verti- cutting also helps the plant to stand upright with leaves pointing to the sky. “This means that they can absorb more sunlight and this, in turn, generates healthier plants and root systems. And the regular
approach also dramatically reduces the stress of the end-of- season ‘rip out’ renovation techniques.” Ian says that, by a process of
their own experimentation, greenkeepers have developed these strategies to control thatch by regularly performing verti-cutting. By cutting in four directions - up, down and twice diagonally - a really thorough job can be done. “And greenkeepers can then alternate each of the four directions for each subsequent one-pass, regular treatment” he says. Excessively deep scarifying should be avoided as this can cause ‘cubing’, which can destroy root structure and lead to total green failure. “By setting verti-cutters at the level position, where the blade just touches the line between the rear roller and the front roller, this can be avoided.
“By increasing the depth in 0.5mm or 1mm intervals you’ll be absolutely amazed at the quantity of material removed, but there’s no risk of ‘cubing’ and the surface can be played on straight away.” Ian says that hundreds of clubs have reported significant improvements in the speed of play with this policy of regular mechanical treatment. “And mowing heights can be kept at a minimum of 5mm. “For exceptional competitions it could be reduced to 4mm, but only if there is a window of good weather to allow rapid recovery” he adds. “The look of the green also
improves with the 5mm leaf length - healthy plants have a healthy colour.” “In the past many have traditionally top-dressed every year and, if the thatch problem has not been addressed, this leads to black layer formation. Different decomposition rates of this thatch can then alter levels. Through season thatch control helps eliminate this problem.” Vitally, the experience of
greenkeepers is that if the speed is good enough no-one comments on the need to lower the height of cut on the green. “And there’s no pressure from players to reduce grass height and take that first step towards a cycle that will lead to bowling green ruin.”
www.dennisuk.com
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