How a golf club can survive the drought

Alistair Dunsmuir
By Alistair Dunsmuir April 22, 2012 11:28 Updated

How a golf club can survive the drought

With drought orders and hosepipe bans already in force in many parts of the UK, there has never been more of a need to ensure that every drop of supplemental water applied as irrigation to the sward is needed and used effectively by the turf. Many documents, instructions and papers have been written and delivered on the subjects of turfgrass irrigation design, equipment, installation, maintenance and operation, but little mention is made of how much water to apply and when to apply it.

An irrigation system is part of the overall maintenance package for turfgrasses and as with any element of turf maintenance equipment it must:

• Be designed for the purpose intended, to irrigate the designated areas, evenly and within the irrigation time cycle

• Be installed to industry standards and set up to operate within the design parameters

• Be serviced regularly to ensure that it operates correctly when required

• Have an operator trained in all aspects of its operation and safety.

Once all of the above parameters have been met, one can then safely begin to assess when to use an irrigation system with the ultimate aim to enhance the overall quality, visual effect and subsequent playing quality of the turf. As such there is a need to:

• replenish water in the soil lost through evaporation and transpiration that has not been replaced by natural precipitation, and

• prepare the playing surface for a particular maintenance operation such as to aid the incorporation of fertilisers and / or top-dressings, as an aid to the germination of seed or to help in the establishment of newly laid turf. However, these practices may be discouraged when water usage is at a premium

‘How much water to apply?’ is one of the most difficult questions to answer as there are so many variables which need to be taken into consideration.

To be able to estimate water requirements for turf it must first be known at what stage a lack of water becomes detrimental to grass growth and survival. Allowing soil water to deplete so much that the grass dies (permanent wilting point), or keeping it at field capacity when the soil is most susceptible to destructuring and compaction, are both extremes. A mid-point exists when adequate growth will occur without extreme repercussions of either too much or too little water.

Evaporation, transpiration and precipitation rates vary considerably throughout the British Isles. The ability to accurately calculate irrigation need is necessary to both conserve water and maintain a quality sward. Only the required amount of water should be applied; too little and the sward will die, too much will both damage soil structure and waste money as well as precious water. In addition to the scientific calculations associated with automatic computerised irrigation systems, an experienced course manager is able to assess when and how much irrigation the sward requires by footprinting or observing soil moisture in the profile when changing the pin position. It is important that he or she resists the demands of various club officials to irrigate when it may not be necessary, as indiscriminate irrigation will be detrimental to both the sward and the rootzone.

The constituents of the rootzone and levels of soil compaction can play a significant part in water availability, as this can seriously affect the depth of rooting of the sward. Where there is shallow rooting there is considerably less water available to the sward and the application of water may need to be carefully controlled. Where the rootzone is compacted this will also undoubtedly affect the infiltration rate of both natural precipitation and irrigation.

To replenish water in the soil lost through evaporation and transpiration one has to establish an estimate of the water requirement which will be affected by:

• Soil moisture deficit (SMD)

• Potential evapo-transpiration (ETp)

• Precipitation (such as rainfall).

Although now largely superseded by computerised irrigation systems, the application of irrigation water can simply be determined by maintaining a water balance sheet, which is nothing more than a profit and loss account; water losses being through evapo-transpiration (ET) and water gains through natural precipitation or irrigation. This will result in a calculation of the SMD of the sward. In explanation of the above terms, the SMD is the amount of water required to bring the sward back to field capacity, whilst figures for both natural precipitation and evapo-transpiration can be obtained either locally, from the Met Office or most accurately via an onsite weather station linked to a computer.

Although a water balance sheet determines the requirements to bring the soil water to field capacity, this, in fact, is rarely done during the season, as the soil is at its most vulnerable to compaction when at field capacity. If the soil is religiously brought back to field capacity, not only will soil structure be destroyed but any subsequent rainfall may cause run-off and also remove valuable dissolved nutrients from the root zone. For this reason only 55 to 65 per cent of the allowable depletion (in millimetres) should be applied as irrigation, where an allowable depletion of up to 50 per cent of the available water may be desirable when the soil is at field capacity. The available water being a calculation based upon the depth of rooting and constituents of the root zone.

As mentioned previously a visual assessment of the turf is the most common way of determining whether irrigation is needed. This method is very subjective and based on the reaction of the grass plant to water stress and the experience of the individual turf manager.  Visual symptoms include:

• darkening of grass colour,

• reduction in grass clipping production,

• footprinting – grass taking time to stand up after being walked upon,

• localised drought on high spots prior to droughting in other areas.

From these symptoms it is impossible to know precisely how much water is needed or whether stress was caused to the grass before drought symptoms were noticed and water applied. Observation of soil samples, for example when changing pin positions on a golf course, is the simplest, most widely used and probably the best method of assessing soil moisture in a practical way.

Nowadays various scientific instruments also exist to measure soil moisture content without the laborious nature of soil sampling or production of a water balance sheet, and these are becoming commonly used by turf managers to ensure only the correct amount of irrigation is applied. In general these instruments have the advantage of immediate, accurate, readings, and include:

• Theta probes

• Tensiometers.

Theta probes are probably the most commonly used for measuring soil moisture in sports’ turf and provide a useful measurement which is not dependent on the knowledge of previous rainfall, irrigation or weather conditions.  As soil conditions vary not only from green to fairway to tee but also within a green, the advantages of some probes lie in their portability, however, in-situ measuring devices do ensure a more realistic point measurement for comparison which can be linked to computerised irrigation software.

Having established how much water to apply and when the application is required it will be necessary to convert this requirement in millimetres into irrigation run time in minutes.  This is achieved by using the calculated precipitation rate for each different type of sprinkler and is dependant upon the designed operating pressure, nozzle size, spacing and arc configuration. Modern computer control systems will, however, automatically calculate the run time from millimetre requirements.

Finally, before irrigation can be programmed it is necessary to determine:

• localised infiltration rates, as it may be necessary to repeat the cycle to ensure penetration of the correct amount of water into soils with low infiltration rates

• the inclination of the playing surface which can also seriously affect infiltration rates

• wind strength, as it may be necessary to postpone or extend the irrigation time cycle in a period of high wind speeds.

As water is obviously a necessity for plant growth, as well as an ever increasing precious commodity, its correct use and application is essential. Modern irrigation systems designed to high standards, and with sophisticated computer controls, plus daily input from the turf manager, should be used to apply only that amount of water required, and not just 10 minutes per station per night. Conservation of our most precious resource is now essential.

Adrian Mortram is the managing director of Robin Hume Associates (RHA)

Alistair Dunsmuir
By Alistair Dunsmuir April 22, 2012 11:28 Updated
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1 Comment

  1. Golf GPS Navigation (@golfgpsreveiw) April 22, 11:43

    Interesting… How a golf club can survive the drought http://t.co/77GqJKyn

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