Regular watering is the most important pre-condition for successfully maintaining a lawn through the long, hot, dry summer in Mediterranean climates. With the specific, spring tasks hopefully completed, such as feeding and de-thatching, and together with regular mowing, the key to lawn care is a matter of appropriate watering.
In dry climates, to give the grass the amount of water it needs to be lush, green, and beautiful, it is necessary to reduce its area. Lawns in Mediterranean climates require between 750 and 1000mm of irrigation water per year. (750mm = 750 liters per square meter) so the smaller the lawn, the greater the chance of supplying it with the water it needs.
Automatic sprinkler systems are the only effective means of both achieving satisfying results and managing the water resource efficiently. Ideal coverage is attained when the spray from one sprinkler reaches the other adjoining sprinkler. It is a mistake to place the sprinklers at a distance whereby the sprays from each meet in the middle.
On the other hand, water should be applied at a rate at which it can be absorbed by the soil, without wastage from run-off. This necessitates the use of nozzles that have a low flow rate, meaning those that emit relatively small volumes of water per unit of time, expressed in liters or gallons per hour. In order to achieve as even a distribution of water as possible, sprinklers that cover smaller areas, like those placed in the corners of the lawn, should have lesser flow rates than those covering larger areas.
With regard to quantities, ideally, volumes should be calculated according to the evaporation rates for any particular location according to the month of year. These can be obtained from local meteorological stations. Perennial, warm, climate grasses need about 50% of the daily evaporation rate, although only in rare cases is it necessary to water everyday day. On the contrary, established, perennial lawns perform better in the long run, when the interval between waterings is spaced out as far as possible.
An alternative method of determining the amount of water at any time is to insert a pole into the soil in order to measure the depth to which the moisture has reached, after a measured period of time. Bearing in mind that some of the lawn types suitable for hot, dry climates can send roots down to a depth of a meter (3ft), it follows that watering can be deferred even if the topsoil layers have dried out. Perennial varieties like Bermuda grass, Zoisia, and Kikuyu, if established, can suffer a certain amount of neglect and recovery nicely after watering, without incurring any long-term damage.
To save water, irrigation is best carried out in the absence of wind, and to avoid encouraging fungal infections, shortly before dawn. From this point of view, the early evening is the very worst time to turn on the sprinklers, as the long period of 100% air humidity is the ideal breeding ground for harmful fungi. It follows therefore, that installing an automatic timer, is not a luxury, but rather an essential tool for lawn care in a hot, dry climate.