There are many factors that contribute to the success of a lawn. A major problem is compacted soil because it lacks oxygen in the root zone, and does not allow for the adequate infiltration of water. Other factors include an appropriate mowing regime, a consistent feeding program and periodic de-thatching. Proper watering though is still the most important factor.
How much to water depends on where you live and the lawn type you have. The perennial grasses in general use in hot, dry climates, such as varieties of Bermuda, Zoisia, Kikuyu, or Paspalon, “consume” moisture at some 50% of the daily evaporation rate for a particular area. This average figure during the summer months is around 8mm per day, which means that lawns need some 4 liters per square meter per day. Contact your local meteorological station, to find out the figure for your area.
The next thing to know is how often you should water the grass. The grass types previously mentioned are deep rooting and actually do better on less frequent, but longer watering because this allows the roots to grow deeper into the soil, making the grass resistant to drought, pests, and disease. Assuming that the depth of soil is over 50 cm, then an established lawn can be watered every 7-10 days in heavy, clay soils, 5-7 days in medium soil, and perhaps 3-5 days in light, sandy soils.
For example, I water new lawns 3 times a day during the first week, once a day during the second week, and so on, so that by the end of the summer they will be irrigated once a week, but with proportionately greater amounts in accordance with the changing frequency and those lawns are just as green as if I watered it every day.
Here is how you can calculate the amount to water in a particular area, where the daily evaporation rate is 8mm, the area of lawn 30 square meters, and the soil of a medium/heavy type.
Quantity (liters) = Average daily evaporation rate * 50% * Area of lawn (square meters) * Interval between watering
Quantity (liters) = 8(mm) * 50% * 30 (square meters) * 7 (days) = 840 liters
How long should you water for? Just divide the quantity that is required by the flow rate. The flow rate can be discovered by registering how much water the system emits in say 10 minutes, and then multiplying that figure by 6 in order to arrive at the amount per hour. For example, if the quantity required is 840 liters, and the flow rate is 500 liters per hour, then watering time = 1 hour, 40 minutes.
This method only works satisfactorily if the irrigation rate is low enough for the soil to absorb it. If there’s a lot of run-off from your lawn, then you should change the sprinkler nozzles to ones that emit less water per unit of time.
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