Suddenly working late / starting early, needing to go there / do that, results in “oh my god you said you would water the garden for me” scenarios…..or, just as bad,….you are going on summer holidays and the forecast is mid 30’s with a couple of 41-45’s thrown in to really fry that harvest before it’s even put in the pan. And no, sadly, you can’t rely on Master / Miss ‘X’ to water again after that last fiasco.
So how best to minimise water needs and what is the best way to irrigate your productive patch?
Warm season veggies really get me excited. Tomatoes are a must…the smell of the leaves alone tell you that summer is coming and yes we’ve all heard it before but it’s true…they taste so much better than any you can buy. Zucchini, sweetcorn, capsicum, chillies, beans, basil, cucumber, pumpkin, lettuce and eggplant are just a handful of what’s on offer in the wonderful Spring /Summer/ Autumn growing period.
But just as they are growing so well, those temperatures start to climb. So how to keep them growing?
Organic matter in your soil
Home compost, purchased compost, manure, broken down pea straw from previous crops, old potting mix it does not matter (although manure is great for nutrients), organic matter in your soil is the best for holding moisture (and nutrients) and releasing it to plant roots.
This will improve sandy soils as well as clay for various reasons but put simply for veggies and water retention…Organic matter, sorry. I’ll say it again in another way…compost and manure.
Plant thirsty together and tough together
Many herbs such as oregano, marjoram, thyme, rosemary, sage and plants such as artichokes and fruit trees will not need loads of water once established. So why plant them with moisture lovers such as lettuce, basil, snow peas etc.?
Zone your plantings for their water needs. If you have an area that naturally holds more water then use it for your thirsty plants.
Mulch insulates the soil, conserves moisture and helps stop weed seed germination. Remember weeds are sucking that moisture from your soil.
Short term soil feeding mulches like Pea Straw are ideal for vegetable gardens as it will generally last until it is time to rotate your crop. Then the remnants can be dug in to improve the soil structure. And hey, the peas are tasty too.
For longer term produce plants like fruit trees, a longer term mulch could be used.
Consider the need for irrigation
Ok you’re busy, or going away, or forgetful (damn, we drained the tank again).
Sometimes an investment in irrigation is needed. If done correctly, your summer crops will pay you back for many years to come.
SO LET’S GET STARTED
(A) Get a timer
Cheap and simple:
Manual Twist timers that allow up to 2 hrs watering (not that you will need that long) are cheap and can run a soaker hose, sprinkler system or drip system off mains or tank with a pump but someone needs to do the twisting on a regular basis. For gravity fed tanks you will need to find a low pressure twist timer – this might take some hunting.
Battery operated tap timers are often a better choice if you are busy or heading away. You can set a start time, choose irrigation days, how long they run for, start them manually if it has been an extra hot day or even switch them off if it has been raining. Ask for the best 9V battery operated timer with a low battery indicator, and an internal filter and multiple start times (if needed). A 9V Battery will last about a year. Good ones are Rain Sensor compatible and simple to use. You can also attach an alternating valve so it will automatically switch to water 2 different areas for different lengths of time if needed.
A bit more substantial:
For larger produce gardens where there is not enough water pressure to water it all at once you will need an Irrigation Controller and Solenoids. To the uninitiated these may look complicated. Put simply though, think of the controller as an alarm clock. A solenoid is a low voltage on/off valve. Instead of buzzing at a pre-set time, the controller sends a low voltage current through connecting wires to the solenoid so that it will open for the pre-set period of time.
But for this article I will concentrate on the use of battery tap timers.
(B) Get a rain sensor
So you’ve waited all year for that balmy summer holiday and after you have set up your automatic produce irrigation system you head away only to find it rains the whole time….yes it’s happened to most of us… Not only are you sick of the rain…so are your veggies as they get a double dose of watering as precious water is applied when it is not really needed. All but the cheapest of timers are now rain sensor compatible these days.
Think of a small tube full of leather washers with a wire connector in the middle. When it rains the washers swell up disconnecting the wire connector, when it stops raining and the washers dry out and shrink, the wire is connected again. It is a simple method of breaking the circuit so that a Tap timer/Irrigation Controller will only turn on in dry conditions. Relatively low cost means a fast payback on water savings.
(c) Drip irrigation system
Once you have automated your water supply you can water your produce garden via sprinklers, sprays, soaker hose or drippers. I have found pressure compensating dripline (Drip eze) to be the most efficient and economical method of irrigation for a number of reasons:
- Water is only applied to the root zone so there are no fungal problems sometimes associated with overhead watering onto foliage.
- Foliage can also stop water from sprinklers reaching all areas.Minimal water loss due to evaporation or overspraying.
- Even spacing of the drippers (30cm), and maximum output of 2 litres/hour/dripper means a uniform application to all areas.
- It also allows you to measure exactly how much water you will be applying per hour.Minimal maintenance means it can be used year after year.
- Even spacing of drippers coincides with spacing of many produce plants.
Although on the surface the drip spacings of 30cm appear to leave dry patches in between, below ground, the water will fan out so that the moisture zones meet up. Think of 2 umbrellas next to each other with the tips of the umbrella being a dripper. NB. Not the case in very well drained sandy soils with no organic matter.
(d) Basic installation
If you only have a small produce garden I would advise installing a 25psi pressure reducer after your timer to ensure you don’t ‘pop’ your system.
Run 19mm poly pipe (or 13mm for small areas) as the main water feeder to your produce area and use 19mm to 13mm reducing Tee fittings to attach each ‘run’ of drip line. Generally space the ‘runs’ about 30-40cm apart for produce. These will be dead end ‘runs’ so use an end plug at the end or simply fold over the end (kink it) and hold in place with a 20mm ratchet clip. By kinking it, this will allow you to unclip and flush out the system if needed.
At the start of each run it is an idea to install a quick shot off valve so that you can turn off the water to that part of the garden when not in use. Be sure to hold each fitting in place with ratchet clips.
Hold ‘runs’ in place using irrigation pegs, bricks etc.
When you need to dig over the area etc. simply fold back the ‘runs’ to allow easy access without damaging the pipe.
In some situations, rather than folding the ‘runs’ back out of the way, you may need to install poly click on connectors (same as most click on hose fittings), so that the ‘runs’ of dripline can be carried elsewhere while you are digging/replanting.
Although designed to be anti-syphon, it is advisable to install a Vacuum Breaker at the highest point of the system. This will allow air to be enter the system once turned off rather than suction being placed on the drippers, which could then be blocked by soil particles. If your tap timer has a built in filter no extra filter will be needed. If using a twist timer, installing an in line filter is recommended for your drip system.
To conserve moisture even more, the dripline can be covered with mulches such as Pea straw or Lucerne.
(e) A little bit of maths
What flow rates and how many metres of drip line can you run?
Keep in mind most tap timers will restrict the flow from your tap so measurements should be done when the timer has been attached. Keep in mind that drippers emit 2L/hour at 30cm spacings, or 6.66 litres/metre.
Turn your tap full on and time how long it takes to fill a 9 litre bucket e.g. 20 seconds / 9 litres.
Divide 20 by 9 = 2.22 seconds / litre.
So for 1 minute, i.e. 60 seconds divide 60 by 2.22 =27 litres/minute. Then for 60 minutes, 27 x 60 = 1620 litres / hour.
Assuming about 75% of this is deliverable in summer due to drop in water pressure and friction of fittings etc, you would get 75% of 1620, i.e. 1215 litres/hour.
Since the dripline can deliver 6.66 litres/metre, this would mean your line could deliver 1215 / 6.66 = 182.43 litres/metre dripline possible per hour. Keep in mind maximum runs off feeder pipe is around 85metres.
Most domestic produce gardens will require nowhere near this so feel confident.
(f) How long, how often, and when?
“When” is the easy one – early morning is best. Automatic systems are currently allowed between 6-10am in Melbourne when using mains water. Even if you have a tank with a pump early morning is best.
How long and how often ? Ah yes, this is the tricky question.
The answer depends on how well your soil retains moisture, what part of the growth cycle is your crop in, average temperatures, and how long that piece of string is
There are a few tips to guide you though.
- Young crops will in general need more water during their growth phase. For example tomatoes appreciate water earlier on but for the tastiest fruit a bit drier as fruit is maturing is better.
- Wedge a cylinder, such as a large coffee tin with the base cut off, into your soil. Slowly pour 2 litres of water into it allowing time for it to soak in. Over the next few days poke a stick in (e.g. thin bamboo stake) and see how deep the moisture has been retained.
- Most summer vegetables are quick growing with rapid root growth. Opting for more water is often better during growth phase.
- Remember drippers emit 2 litres/hour so 5 minutes is a waste of time – longer is better.
- Longer, less frequent watering cycles encourage deeper root systems that are then more protected on very hot conditions.
- All plants can wilt on hot days- this is normal. You just want to be sure they look ok the next morning.
As a vague, very general guide for good, organic rich soils irrigate for 1 hour every second day for young crops, easing to 1 hour every 3rd to 4th day as they mature. You will need to fine tune depending on crop, soil, and temperatures.
So if you are busy and love growing your own food. Consider investing in an automatic irrigation system fitted with a rain sensor.
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