How much water and how often?

Date Posted: 29 November 2017 

“How long to I need to water my lawn for and how many times per week?” This would have to be some of the most commonly asked questions and for good reason “How long to I need to water my lawn for and how many times per week?” This would have to be some of the most commonly asked questions and for good reason

Most people want their lawns to get the right amount of water but no one wants to over water given the price of water.

The answer is a bit more involved that most people think and without trying to over complicate the issue, it depends on the following things:

  • The type of soil you have

  • Type of lawn you have

  • Watering method

  • Position in the garden

  • Which season we are in

Soil Type:

The type of soil you have will determine how much water it can hold and how penetrable it is which is a key piece of information to understand how much water your lawn will need. For example, a clay soil can hold twice as much water as a sandy soil but it takes longer to penetrate in.  Using this information, if you had a Clay soil, you can water less frequently (because it holds more water) but you’re best to water with a method that delivers the water in a slower fashion like drippers or a eco rotator type sprinkler. Water tends to run off clay soils if you apply it too fast and can also pool in low spots. 

On the contrary, sandy soils have the potential to absorb water quickly but don’t hold as much so more regular waterings for shorter periods of time would be in order.

Type of lawn:

Knowing what type of lawn you have can help you know how often and how much. Some lawns are more drought tolerant than others. For example lawns like kikuyu, couch and buffalo use far less water than lawns like tall fescue, rye and blue grass. Typically, lawns like tall fescue, rye and blue grass are thirsty and need three times as much water as a couch or kikuyu lawn.  On the other hand, lawns like Kikuyu and Couch are truly drought tolerant. Once established, there is enough natural rainfall in Adelaide to keep them alive so technically do don’t need to water them at all! I wouldn’t recommend this type of management but if you do go down that path though, you’ll find that if you don’t water them, they will dry out and go brown during the summer but they will begin to recover when the autumn rains come around.

Watering method:

The most common ways to water your lawn include pop up sprinklers, sub surface drippers and hand watering.  The most efficient is sub surface drippers however they deliver water to your lawn very slowly meaning you have to leave them on for longer and more frequently than you would for pop up sprinklers. Pop up sprinklers deliver water quickly so you don’t need to leave them on as long or as often.

Which season we are in:

Daytime temperatures and the volume and frequency of rain will of course play a major role in how much and how often you need to water. Heat effects the evaporation rate in the soil and increases the transpiration rate of the lawn meaning more water is required. Wind dries out the soil faster and then there is competition from other plants around the garden vying for the same water.  Obviously, the warmer it is, the more frequently you’ll need to water.

Position in the garden:

This is a no brainer but I’ll say it anyway – lawns in the shade will require less water that lawns in full sun so keep this in mind when deciding how much water to apply

Summary:

As you can see, there isn’t really a one-size-fits-all answer because circumstances can vary so much – and I haven’t even started on wetting agents! (those that know me know that I have a tendency to bang on about wetting agents but that’s probably a topic for another day, but I will say this: Wetting agents have the ability to drastically reduce the amount of water you apply to your lawn!

I know.  I haven’t answered the question… How much and how often…  The real answer is as much as the lawn needs but if I had to make some generalisations, most warm season lawns (couch, kikuyu and buffalo) in South Australia need around 25 – 30mm per week of water to keep them green during the warm months of the year (more in heat wave conditions).  They will survive on less but they’ll potentially loose their colour and go brown till more water is available again.  When you water, you want to get the soil wet down to about 50mm deep. You can test this by digging a small inspection hole after watering. If it didn’t get down that far, water for longer. If you didn’t get any water penetration at all after watering check that your soil isn’t non wetting. By doing this you soon discover how long you need to water for. You’ll also discover how long it takes for your soil to dry out.  For what its worth, I have a Santa Ana lawn growing in full sun, on clay. Using a sub surface drip system, I water twice per week during spring and summer for about half an hour which seems to do the job. 


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