Effective Turf Irrigation

Water costs money.  Wind also costs money - because it wastes water.  So does hot weather - irrigation is less effective when the day is hot, too easily evaporated.

It is critical to get water into the ground where it can be most effective.  Plenty of leaflets, web pages and word of mouth have been produced about making irrigation more effective, but most advice comes back to just a few key areas:

• water when there is little or no wind - that way there is less evaporation of the water during the time it is in the air and with low wind the application of the water from sprinklers is more evenly distributed and is delivered to the target area, not somewhere else.
• avoid watering when it is hot - there is more evaporation of the water in the air before reaching the target, the grass surface is usually hot, meaning some greater losses from evaporation and transpiration on the grass and the ground near the surface is also hot adding to water losses

Data from Australia [Perth in summer] indicated losses of as high as 85% of applied water on hot windy days.  Put the other way - the most water you can expect to get onto the grass is 15% of what goes along the pipe!  That is very low.

Another variable worth considering is water droplet size, with smaller droplets likley to be more easily lost  and never contribute to irrigating the turf.  Pressure and sprinkler head design are some of the issues to consider, and also think of this in conjunction with the first two points.  There is an ideal size range of droplets, but larger rather than smaller drops is generally better.  Easily seen on a windy day as you watch the fine droplets being blown away. [ see above in the photo]

Some of these can be rectified to some degree, and there are alternates in irrigation design and system approaches.

System design - consderation in switching to something such as KISSS is worth considering.  This is a sub surface textile wrapped concept in which the water is delivered underground at the bottom of the root zone.  A little more expensive to install it can repay costs in a short period with much lower water use.  Reductions of 50 -70% in water use have been achieved.  And the turf area is available at all times, even while irrigating.  See www.kisss.com.au - it is an Australian concept and has been used for over 12 years.

But most opt to better manage sprinklers by better timing eg evening, when conditions are better for irrigation - lower temperatures, less wind especially.

BUT....low pressure  sprinklers with superior nozzle design that creates superior droplets can also be effective in doing even better.  For example with sprinklers designed for 200kpa [ in essence drip systems] with low volume sprinklers operating at low pressures.  Examples of this include using sprinklers similar to those used in tree crop growing, but with an even spread of irrigation water across the whole of the wetted diameter, or newer specific turf type sprinklers.  Our own experience is that water use can be reduced at least 25 -40% over ordinary higher pressure pop up sprinkler systems.  Also adaptable to use with timing systems.

Maintenance of your own system is critical to efficiency.  Avoid watering the concrete or road, keep nozzles clean and avoid overwatering with better frequency and timing management.  Overwatering usually results in sedges and nutgrass weeds, ultimately severly compromising the turf quality. 

Water is NOT a substitute for adequate nutrition, and remember that mostly when you mow, you remove the clippings - and nutrients go with them; so at least try to reuse the clippings on gardens or for mulching.

Irrigation in the dry tropics here in Darwin is really needed for a good turf .  Irrigate wisely for a better lawn, at less cost.