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ALTHOUGH it may be hard to imagine as you read this, but some of you will be struggling for water this summer. It seems that every year the well runs a little drier and the threat of global warming looms a little larger. We never really miss water and, to a certain extent, the climate in the UK is on our side. So we may have to go a couple of weeks without, but on the whole we know that rain is probably around the corner. However, when times are dry, even for brief periods, the effects of water applied through the irrigation system become apparent, or perhaps it should be more correctly stated that the effects of non- uniform application of water become apparent.


Uniformity


An irrigation system that does not apply water evenly will cause problems; this is referred to as the Uniformity of the irrigation system. Today many golf courses have fully computerised automatic irrigation systems; these systems can calculate and inform the turf grass manager the application rates, run times and even fault find. They allow the manager to quickly change irrigation head run times or to have several irrigation programmes stored to allow for quick changes to the system in response to changing environmental factors. Yet for all of this flexibility, the uniformity of the application is unknown and first indicators that all is not well may be at the first signs of the death of the turf grass. At present, uniformity does not cross the minds of those in control of the irrigation system, especially when rainfall is usually adequate or when water availability is not an issue. This, however, is


Calculating the Distribution Uniformity of Irrigated Areas by STEVE PRINN, Askham Bryan College


rapidly changing. An irrigation system which delivers water uniformly will not only save money but, in sports surface management terms, ensure the consistency and playability of the surface. Irrigation uniformity is an important factor in agriculture where most of the research has been carried out, the effects of irrigation uniformity on crop yield has been well researched and documented. While golf courses and sports grounds are not huge users of water in the wider context, they are very public users and, in some respects, easy targets for criticism; this alone means that irrigation use at these facilities needs be seen to be respecting the wider environmental implications of applying thousands of litres of water in a season. Modern construction


methods applied to the majority of golf courses and major stadia built in the last few years, coupled with the use of predominantly sand based root-z


zones, has


increasingly seen irrigation used as an important management tool for maintenance. With an increase in the


need to apply more water there is an increase in the need to ensure that the water is actually applied in a way which guarantees that the whole of the surface receives sufficient moisture to enable the turf grass to not only survive but to provide a surface which meets the increasing demands of today’s sports men and women. The turf grass needs


moisture at all parts of the growing cycle, without it, its metabolism will cease to function and the plant will die. If there is a shortfall of the precipitation rate (pr), to the evapotranspiration of the turf


grass (ETT), then supplementary


irrigation needs to take place. It is, however,


important that the amount of irrigation applied to a given area is correct; too much and the turf grass will become prone to damage from wear, insects and disease, too little and growth will slow and the plant will wilt and eventually die. The turf grass’s need for water is variable through out the year according to environmental factors such as temperature, humidity, and wind speed and light. Individual turf grass species also have variable water demands. There is, therefore, a need


for the irrigation system to deliver the correct amount of water to the correct place, to ensure that the surface remains uniform and playability of the surface is maintained at acceptable standards. Irrigation uniformity is


important, and is founded on a basic premise -a


all irrigated


areas should receive the same amount of water. If water is not applied uniformly then a number of consequences will occur:-


• Some areas will be over watered.


• Some areas will be under watered


• Some areas will receive the correct amount of water


• And some areas may not receive any water at all


Whichever of the combination of consequences that occur will, to a greater or lesser extent, affect the health of the turf grass and likely to produce a playing surface which may not perform to the required standards.


How to Carry out a Survey


Catch-c cans are placed at 3m


centres across a golf green in a grid pattern. The catch cans can be any type of container as long as they all have vertical sides, with a thin edge/mouth and the diameter of the opening needs to be identical, -t


or soup cans -d


try baked bean depending


on taste. To prevent the containers being knocked over by either the wind or the water stream, put golf balls inside them, although you should not do this test if it is too windy, certainly no more than 5mph. Irrigation heads/ valves


should be operated in the same pattern as they would be during a normal irrigation cycle and run sequentially if required; this will ensure the test cycle is as close to operating conditions as possible (Wilson and Zoldoski 1997). Run the system for double your normal irrigation cycle to ensure you have enough water in the cans to record it. Pour the water collected in


each container into a measuring cylinder and record the figures. It will help identify problems if there is a sketch made of where the measurements were taken from. Total up the amount of the water collected and the


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