Bowling Green Irrigation 
Irrigation is routinely overapplied and is a major contributory factor in the gradual deterioration of a bowling green surface. A wet surface might arise from not removing dew early enough in the morning, but more likely and significantly it will be excessive, or high volumes of, water being applied with the green not being able to transmit the water downwards at a suitable rate, especially where a thatch layer is retaining the water.
If the start of play begins and maybe 10.00 am then it is important to ensure any watering has finished a suitable time before play commences to allow the surface to dry adequately.
A surface that is routinely wet or consistently moist is prone to compaction. Not allowing adequate time for water infiltration and percolation through the rootzone before maintenance work or the start of games will result in a gradual and accumulating extent of compaction. This can also be a significant contributing factor in a negative feedback cycle which encourages shallower rooting, increased thatch development and reducing the competitiveness of desirable bowling green grasses of red fescue and browntop bent, whilst increasing the environmental conditions which are more suited to Poa annua colonisation. This in turn will also lead to a more disease susceptible turf, a requirement for increased irrigation to maintain plant health, increasing surface casting by earthworms, a more protected environment for grubs to develop, increasing fertiliser inputs and increased mowing requirements, all making it much harder to produce a satisfactory playing surface for a consistent and long period of time.
Some greenkeepers mistake the encroachment of Poa annua with the need to adapt maintenance practices to maintain a green, often relatively lush, sward. Unfortunately, the action to be taken at an early stage of encroachment should be to reduce the conditions which are making the environment more competitive for Poa annua and adapt activities back to those more suited to the fescue and bent grasses, stressing out the Poa before the problem becomes more extensive.
Overwatering contributes to a heavier and slower green, requiring greater effort and exertion form bowlers to deliver a bowl towards the jack. This situation is most undesirable and is a major problem on many greens, being especially noticeable during the early and later parts of the playing season when ground conditions are typically wet to moist, in contrast to the drier conditions typically experienced during the peak of the summer months.
The time period for the drying of the surface and transmitting of the water through the soil profile will depend on the condition of the green, but one-hour before any activities might be considered as the latest time for many greens in which watering should be completed by, being more for water retentive thatch greens, however, for specially constructed sand-profile type greens which can drain very rapidly then this might be nearer the actual match starting time.
Where an automatic pop-up sprinkler irrigation is available then this will need to be used with discretion because it is so easy to adjust the timer to give a little bit extra each application, or to increase the frequency of applications.
Unfortunately, the ease and convenience of application, which is also a significant time saver where greenkeeping staffing is limited, is also one of the biggest problems with automatic pop-up systems: Judicious, and careful watering is the order of the day.
The finer desirable grasses will manage well on low amounts of water, but this must be supported by a good depth of root growth which should ideally have been encouraged by routine aeration and other correct maintenance practices. Failure to develop a good root system will otherwise cause the sward and playing conditions to suffer, resulting in a poor overall quality of playing experience and increasing complaints from members and visitors.
Watering to a good depth (this will depend upon how much rootzone is present) and then let the roots explore for moisture in the lower profile as the surface gradually dries through evapotranspiration.
The importance of good root growth cannot be overemphasised when it comes to effective irrigation practices and water consumption. For example:
• if a green typically has a sandy rootzone of 100mm, it may potentially have available water at 12% within the profile (meaning 12mm of water will be retained within the soil if at field capacity).
• the roots will ideally explore to all of this depth.
• water usage for a strong growing sward is commonly estimated as 25mm per week, during the summer period, as available water becomes harder to extract from the soil the grass plant will actually start to reduce its need, so this figure is often quoted where continued, relatively strong, growth is assumed to be maintained, but this is not necessarily in the best interest of the production of a fine turfgrass surface during the summer period – some element of natural stress from water restriction can produce a more resilient sward. The 25mm per week figure is also often related to theoretical evapotranspiration figures for grassland maintained at 150mm, being based on agricultural requirements rather than a turfgrass situation. One research investigation for golf green turf consisting of a Chewings fescue and browntop bent sward, identified the actual measured evapotranspiration value as being 65% of the theoretical figure. This has implications for the quantity of water applied to sports turf areas, allowing for potential savings in time, money and water consumption through reflecting on a more considered approach to irrigating turfgrass swards. (Lodge, T.A. & Baker, S.W. ‘Soil moisture content and evapotranspiration rates of thee different types of golf green construction in response to different rates of irrigation’, The Journal of the Sports Turf Research Institute, Vol.68, 1992, pp104-113)
• the supply of water in the above example would last about half a week, meaning irrigation would be needed (assuming no rainfall occurs) about twice a week.
• if, however, the root depth was only 50mm, then available water would typically be down to just 6mm, meaning irrigation might be required on about four times per week.
• more frequent irrigation can lose some of the benefits of intervals of rainfall which would otherwise top-up the available water for a deeper-rooted green but would be wasted on shallow rooted greens.
The quantity of water needed over a growing season will vary each year due to the vagaries of the weather (aiming to replace evapotranspiration losses is a good plan to follow), with a very general guide for the assumption of needing 25mm of water needed per week being:
April – September: 26 weeks: 1475m2 green requiring an average of 12mm (or 0.012m) of applied irrigation per week (sometimes this will be less, others more, but for this illustrative exercise this is a suitable estimate), the reminder by rainfall:
• Total irrigation per week = 17.7m3 or 17,700 litres (˜3,900 gallons).
• Total irrigation per year = 460 m3.
• Total irrigation water cost = estimate of £1.50 per m3 of potable water: £690.
(This assumes that there is no charge for drainage as water is either consumed by the grass plant or lost through evapotranspiration. Water authorities will have a ‘non-return to sewer’ policy, which acknowledges that for the maintenance of sports surfaces, especially bowling greens, not all or any of the applied water is actually wasted and returned via surface drains and sewers for them to re-treat. They may offer a reduction of up to 100% of the drainage charge (which might otherwise increase costs by about another £1 per m3 used) for drainage water, therefore making this aspect non-billable. If a club is paying for drainage costs of water used, then it would be beneficial for them to contact their local water authority and apply for a reassessment).
Where the bowling green has been overseeded, then the aim of watering will be to aid germination and to prevent newly germinated seed from rapidly drying out, yet at the same time encouraging roots to gradually explore deeper into the rootzone. A lighter watering will be required than on an established green because the roots are shallow and just developing.
Hand watering of edges and central areas of a green where wind might have affected the application of water from a sprinkler may need to be carried out to ensure that a relatively even coverage is given and that dry areas do not start to develop. If selective hand watering isn’t carried out then insufficient water coverage during prolonged dry periods can result in the green drying out, resulting in the disorder called localised dry patch, which can be especially pronounced where thatch is also a problem.
The edges of greens will dry out more rapidly than the body of the green, primarily because the turf profile is more exposed at the edges around the entire green. Being adjacent to concrete or wooden edges will also create warmer conditions, especially when these are exposed to the sun, and this will dry out the soil next to the edgings. Sometimes a slightly heavier soil is used for working into the green edges to help reduce the extent of the edges drying out.
Hand watering, including the use of static sprinklers which are moved periodically by the greenkeeper, can be quite time consuming but can provide a much more focused and appropriate degree of application, especially where many greens are not uniformly even and will often contain many shallow depressions and high spots, from which water will run off into the low spots. Automatic pop-up sprinklers will apply water relatively evenly over the surface but will continue to apply water that runs off into low spots until the programme finishes.
To facilitate better water entry into the surface and into the rootzone it is essential to create pore spaces into which the water can more readily move away from the immediate sward surface and not start to be retained in a thatch layer. Shallow spiking, in particular the use of a sarel spiked roller is very effective at creating thousands of tiny holes into which water can be transmitted into the surface layer, is an activity which should be considered prior to each irrigation of a green.