What is a swale
A swale in permaculture is a key earthwork technique that is essentially a level ditch dug along the contour line of a slope and paired with an earth mound (or berm) on its downhill side. The primary purpose of a swale is to intercept rainfall runoff, slowing its flow by catching it in the swale and spreading it out evenly across the landscape. Most importantly, the water is held in the swale and thus able to infiltrate deeply into the soil rather than running off down the hill. This infiltration recharges groundwater, supports deep-rooted plants, and builds soil moisture. It encourages rainwater to soak into the land higher up on the hillside where it is needed most.
What is deep pipe irrigation
Deep pipe irrigation is a strategic watering method that involves delivering water directly to the deeper root zones of plants, typically trees or shrubs, by means of a vertically oriented, perforated pipe buried adjacent to the plant. This technique encourages the development of extensive, deep root systems as plants grow towards the consistent moisture supply.
In contrast, conventional surface watering methods, such as hoses or sprinklers, often result in significant water loss through evaporation and limited penetration into the soil. This can lead to shallow root development, making plants more susceptible to drought stress and less resilient in varying environmental conditions.
Innovating Deep Pipe Irrigation: The Pipe-Free Approach
While the traditional deep pipe irrigation method uses a buried pipe, concerns regarding the long-term presence of synthetic materials in the soil, potential root intrusion, and the eventual difficulty of pipe removal are valid.
As an alternative, a modified, pipe-free approach can achieve similar benefits. This involves creating a deep, narrow channel or hole near the plant’s base and filling this with rocks, pebbles or sand to keep the soil from collapsing into the hole. This method still facilitates deep water penetration, encourages extensive root growth, and minimizes surface evaporation, all without introducing permanent non-biodegradable materials into the garden ecosystem.
If you are installing the deep pipe irrigation watering method at the time of planting your tree then the best option for you be to use a buried piece of PVC pipe since you will need something to hold back the loose soil to create the watering reservoir. In my situation, my trees had already been planted some time ago and I was retro-fitting the swale/deep pipe irrigation method so using an open hole without the pipe was not a problem.
I purchased a 100mm post hole digger for the job. This being the perfect size for an irrigation hole next to my fruit trees. Note also that if you do choose to use a piece of PVC pipe to do this deep watering method at home then a 90mm PVC will slide easily down the hole dug by the 100mm post hole digger. This is the quickest and easiest way to bury the pipe when retrofitting.
You want to place your hole up-slope to your tree so that the water from your reservoir travels downhill TOWARDS your tree rather than away from it. The only acception to this rule is if your tree is in a windy location (although ideally you should have a wind break in such circumstances). If in a windy position the hole should be dug UPWIND (ie on the side that is the main direction of the prevailing winds). This is because trees in windy positions grow their roots towards the direction of the wind as this makes the tree more stable. For a larger tree you may want to dig two or three holes around the trunk to encourage even root growth.
I dug my hole beside my fruit trees upslope and about 400mm from the base of my tree. Ideally I would have liked to go down one meter, however, I start to hit clay and shale at about 300mm in my garden so it becomes more difficult to dig. Just get down as deep as you can – anything is better than nothing at all. When the hole fills the water will soak out from the sides of the hole with the majority of it going towards the bottom – this will promote deep root growth while still allowing access to water for the tree roots when the tree is still small.
After the hole was dug I then filled this to the top with rocks from around the property. You can use anything that is handy – sticks, rocks, bamboo, stuff the hole with hessian bags, etc. Even pebbles, mulch or sand will do the trick but the more gaps that you have for water to penetrate the better. Filling the hole will keep it from collapsing in and also prevent any wildlife from falling in and becoming trapped.
After that I dug a mini-swale (often called “fishscale” swales) that will catch water as it runs down the hill and will feed into my irrigation hole. You can make the swale longer to channel more water to the tree depending on how much water it likes (just be careful not to overdo it and drown your fruit tree).
Over time, the gaps around the rocks will eventually fill in with soil and organic matter but by then my fruit tree will be large enough with a deep, strong root mass and will no longer need my irrigation system anyway.
This image shows a top view of how this should look.
It’s been raining here so now is the perfect time to install such passive irrigation techniques. Why not run outside and create your own watery oasis!?
Jo
