Being Water Wise - Part 5: Smart Irrigation Choices
Unfortunately the average gardener uses twice the amount of water for irrigation than they actually need to!
What is hydro zoning?
Hydro zoning your garden helps you to make the most efficient use of your irrigation. It can be helpful to draw a bubble diagram of your property to help visualise this.
Choose the zones;
-Regular irrigation – ie your vegetable garden or potted plants on a patio – every 2-4 days
-Reduced irrigation – receives irrigation every 4-14 days
-Drought irrigation – only watered during dry spells after plants are established
-No irrigation – not irrigated at all.
By zoning the areas before planting, it will give you information to help make the ‘right plant for right place’ choices for your garden. It helps you to target where irrigation is required and to focus your water use on areas where it is actually needed and won’t be wasted. It is also an efficient use of your time and energy, rather than pulling a hose all around the yard, you can keep your time watering to a minimum and use your time elsewhere!
What irrigation system should I use?
When it comes to choosing your irrigation set up, wherever possible use weeper hoses or drippers. They weep slowly which enables time for the water to slowly seep into the soil. This helps prevent surface run off and helps minimise loss through evaporation. Weeper hoses can also be buried under mulch which helps minimise wastage even more. Put them on a manual timer and you can set and forget.
When you are laying out the hose, wind it through the plants along their drip zone, where the feeder roots will be. Don’t waste water applying it directly by the trunk/stem of the plant. Helpful tip – put markers where you have laid it so you don’t put a spade through it accidentally!
The additional benefit of weeper hoses is that it keeps water off the foliage where fungal diseases or burning can occur.
Using electronic timers are a great way to ensure that your plants do get watered reliably but it is not a ‘set and forget’ situation. You still need to keep an eye on the weather and the soil moisture situation and adjust as required. The timer doesn’t know that it rained or there is still adequate moisture in the soil, it just turns on the irrigation regardless of whether the water was required. Remember to turn these off in autumn /winter as rainfall should be more than enough.
If you are using sprinklers, avoid using them in the middle of the day when evaporation rates and risk of burning are at their highest. The best time is in the morning.
If you have drippers set in pots and you notice that water pours out the bottom quite quickly, reduce your drip rate so the water has a chance to be absorbed or mix Tui Saturaid (see below) into the soil.
How can I prevent unnecessary runoff?
If, when you water, you notice that the water sits on the surface in ‘bubbles’ and doesn’t absorb into the soil or it runs straight through, it may be that the potting mix or soil has become ‘hydro phobic’. That means the soil essentially repels water rather than absorbs it, making watering a waste of time. This often happens in pots or in dry areas of the garden like under house eaves where rain doesn’t fall. There is a product called Tui ‘Saturaid’ which you can mix into the soil and it will redistribute the water through the soil and into root zones.
Alternatively you can mix Yates Waterwise Water crystals into potting mix before using in pots. These crystals absorb water and release it slowly. Helpful tip – mix them in with water before you mix them into the potting mix!
How long do I water for?
It is always better to err on the side of caution when deciding how long to water / irrigate for.
Plants can come back from being dry, but they are highly likely to die if root rot sets in from being too wet. Do some trials with time and physically check how far down the water is getting. You can always increase the time. It’s better to do a deeper water less often than frequent shallow watering. If a plant is watered daily with a sprinkle, the roots will stay close to the surface so they can access the water. Being close to the surface means the roots are more susceptible to increases in temperatures and less resilient to cope with long dry spells. Deep roots allow a plant to access soil moisture that may not be accessible closer to the surface.
The length of time also depends upon the type of irrigation. Sprinklers give out large amounts of water in short times whereas weeper hoses give out a low volume of water and so require a much longer time running to ensure adequate watering.
Soil type also affects irrigation time. Heavier, clay based soil will retain water better and for much longer so they don’t need to be watered for long or too regularly. Be aware that your irrigation does affect your neighbours gardens as well, particularly if you are on a slope.
Start with a short time approx 3 times a week and you can adjust length of time and frequency from there.
If after following our other water wise advice, you still need irrigation, ensure your system and program is as water wise as possible. It can make a huge difference to your water usage and to your plant health.