A Good Putting Surface
(Golf Course News International, August 2002)
Golfers are quick to judge the putting conditions on the greens – and in their eyes it is this assessment that often determines the standard of the course and whether they want to return or not. Course managers know that to achieve a good even and fast putting surface the grass growth must be vigorous, dense and even textured and this surface can only be achieved and maintained when the stress levels within the green are reduced to the minimum.
Interestingly enough it is the top 50-100mm of the rootzone that both illustrates and determines the health of the grass cover. The movement of air, water and mineral nutrients are essential within this region as it is only in this shallow depth that the grass plant secures all that it needs to survive. The effects of an imbalance between these essential factors is readily evident in the putting surface – and unfortunately when symptoms are noticed it can be too late to restore the conditions immediately.
At this time of the year with high rates of water loss, the moisture regime within this depth is critical. Where moisture is limiting aerating with any equipment will lead to disaster with increased dehydration and severe set back to the putting surface. Greens lacking balanced nutrition too will have no vigour to respond. Any form of aerating can only successfully be carried out when the grass plant is in an active growing condition and moisture conditions in the upper rootzone are favourable. Constant probing of the top 100mm throughout the hot summer months remains one of the most important daily actions needed to give peace of mind and plan irrigation.
As the temperatures get higher, water is uppermost in the mind of course managers and yet with automatic irrigation systems now standard on greens over watering can be done – though this is often on decisions of those other than the course manager. It is only the high drainage rates on over-watered greens that save the day – but as can be expected, this surplus water in the top 50mm prevents deeper root penetration and encourages meadowgrass.
Creating an adequate air supply in the rootzone is an ongoing challenge to all course managers. It can only be achieved after the diligent and regular application of cultural treatments that continuously ensure a good air supply where it is needed most – in the top 50-100mm of the rootzone.
Hollow tining is a recognised treatment, but it is despised by golfers because of the disruption it causes. Solid tining, slitting and multi-tining all help considerably in boosting the air supply to root growth. Yet irrespective of the diameter of cores or the spacing between tines the percentage of area aerated is still very small (some 5% of the area).
A dramatic innovation within the last two years has been the concept of ‘linear aeration’ as termed by some; in effect it is a treatment of closed spaced shallow channelling that causes negligible disruption to the surface. In addition to creating aeration to a much greater area of the green (14% of the green area) in one treatment – at the same time there is removal of excessive leaf and root tissue by means of a deep vertical cutting action that stimulates tillering and vigour of growth. Spacing between tines can be reduced below the standard width of 25mm though the penetrating depth to 45mm would reduce at closer spacing (6 and 13mm). Also, there is the option to use 1, 2 or 3mm blades which enable an ‘openness’-though care must be taken to prevent drying out when using the 3mm blade. The high speed cutting action of the blades cause negligible destruction of the putting surface – but significant quantities of thatch and root growth are brought to the surface. These can be removed by using a blower.
Although originally marketed as a scarifier, the precision cutting action, though removing thatch and grass tissue, leaves the surface so undisturbed that play can resume immediately – preferably after a light top-dressing. It is the penetration of this treatment that makes it so much of an aerating tool and the lack of disturbance between incisions that prevents it from being a true scarifier. Turfgrass remaining is stimulated by the air supply and improved water movement. Where the entire thatched grass surface is to be removed or thinned out more severe scarifying treatments would be required.
Though pioneered in Australia with the production of the Graden, Sissis have produced a local model. Essentially the treatment achieved by these units is unique and their arrival on the scene heralds a new approach in maintaining high quality putting surfaces – entirely due to better establishment of air and water exchange within the upper rootzone.
The secondary effects of this cultural treatment also cannot be over played. Not only are mineral nutrients made more available to active areas of root growth, but the condition for aerobic bacterial action within the rootzone are improved a hundred fold. This is vital for the breakdown of thatch and nitrification. Furthermore, visible root growth is clearly evident in the channels a few weeks after treatment. Where the grass thatch is saturated or the green surface has become impervious or compacted, the first treatment of ‘linear aeration’ can generate an alarming amount of bad odour due to the anaerobic action below this layer. In extreme situations organic matter accumulates, nitrates are deoxygenated, become unavailable and grass becomes starved of nitrogen.