If it’s not flooded, it’s drying out. That’s the challenge for gardeners in the tropics, but now the rains have come to an end we have to get our dry season watering regime back on track. Watering methods can provoke debate – allow me to share with you my experience after seven years of trial and error.
The first method I employed was the dripper system. An intricate network of dripper lines, filters and flow regulators that feed each individual plant. It was an expensive and labour intensive system that kept the trees alive, but that’s about all it did. Things were alive, but they weren’t strong and healthy. It turns out the biggest problem with drippers is that they supply water to only a very small area, and as a result plants concentrate their roots in only the area that is being kept moist. Think about it this way, if a plant has a regular supply of water close by, why would it bother growing an extensive root system? As a result they become very dependent on regular watering and if you forget to water them they very quickly become stressed and show little resilience. An additional problem is that because they have a small concentrated root system they aren’t very stable and are more likely to fall over during strong wind.
Next I replaced the drippers with an off-the-shelf micro irrigation system – in other words, a variety of fancy sprinkling attachments that sprayed water all over the place. It looked good but the fine spray seemed to be evaporating in the air and the plants were very susceptible to stress if they weren’t watered at least every second day. So after two years the micro system ended up in a box in the shed beside the dripper system.
Nowadays I have a very simple system and only water my garden once every two or three weeks. And believe it or not, my plants are stronger and healthier than they’ve ever been. The key was to encourage plants to develop a strong and deep root system. This has been achieved by using larger sprinklers that produce larger water drops at a much greater volume. These are left running for at least three hours. That way the water penetrates deep into the ground instead of just the top 10 centimetres. As a result plant roots grow over a larger area and grow deeper as they chase the water further down as the surface becomes dry. And due to the now much larger and deeper root system, my plants have improved their hold on the ground and are less likely to fall over during a blow.
Two to three weeks between watering works well for my plants and soil conditions, but how do you know exactly when to water? Simple. Look at your plants when the sun has set. If they look firm and healthy, then their roots are still able to find the water in the soil. If, however, they look limp and tired after the sun has set then they are no longer able to get the water they need and it’s time to give them a good deep soaking again.
(Published in Cairns City Life magazine, May 2008)