PHOTO: Amy Stross
June 10, 2016

Watering a backyard garden can be cumbersome with a hose, but small-scale gardening doesn’t always warrant the full-fledged irrigation system seen on farms. When the summer heat kicks in, it’s essential to keep garden soil moist. Just as you must stay hydrated to combat the effects of intense sun, so must your delicate crops. The big question is how to best keep soil and crops hydrated without having to spend all day watering.

Before setting up any irrigation system, look for ways to minimize the need for irrigation, because a smaller and less elaborate system can save you time and expense. Mulch is an obvious and important choice, not only for minimizing irrigation needs, but also for protecting beneficial soil organisms that need cool, moist soil to help keep crops healthy. In geographic locations with intense sun and periods of drought, deep mulching can go a long way to reduce the need for an elaborate irrigation system.

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These passive irrigation techniques use the contour of the earth and other creative materials help reduce watering time. As a bonus, they can also reduce costs.

1. Swales

A number of techniques make the most of the land’s elevation contours to passively catch and hold rainwater and fertility onsite. One such technique used in permaculture systems is a swale, which is a trench dug along a contour line with the soil mounded on the downhill side to form a planting berm. This technique can be used on gently sloping land or even land that doesn’t appear to have any slope at all because contour lines can be found on any type of property. Swales can work well on large- or small-scale properties. In my yard, a swale formed the basis for a beautiful front yard edible landscape.

2. Contour Gardening

Contour gardening is a similar technique that includes situating planting berms or raised beds along the contour without the pronounced trench of a swale. Contour gardening can maximize the use of rainwater: slowing it, reducing erosion and absorbing valuable nutrients that would otherwise wash away.

3. Check Log Terracing

passive irragation
Amy Stross

Check log terracing is another low-cost contour solution that uses materials found onsite to slow rainwater on a slope. To create a check log terrace, stakes are pounded into the ground every few feet along a contour line, and branches are laid on the uphill side of the stakes to form a level planting terrace. It is then backfilled with locally appropriate soil and organic matter.

4. Rain Gardening

Rain gardens can also passively collect rainwater. A rain garden is a bowl-shaped shallow depression in the ground. When situated uphill from a garden area, a rain garden can catch rainwater from a roof or patio and passively irrigate crops below it. You can even plant edible crops in a rain garden!

5. Rain Barrels Made Useful

Rain barrels that catch rainwater from a roof are often promoted as an eco-friendly alternative to using municipal water for irrigation. However, there are a few potential problems with this assumption. First, standard-sized rain barrels catch an embarrassingly small percentage of rain and can fill up within 5 minutes during a heavy rain event. This means that most of the rain from the roof is lost, either by going back to the storm drain or by over-saturating the ground around the rain barrel if an overflow solution isn’t properly placed.

Another problem with rain barrels is that the non-pressurized water makes irrigating by hand an active, rather than passive, time-consuming process. I’ll never forget how proud I was when I installed my first rain barrels, only to curse them by the end of the summer after hours of carrying my watering can back and forth between the barrels and the garden. There are a few rain barrel pumps on the market today to pressurize the water, but to date I haven’t found one that works well and is built to last.

To make my rain barrels more useful, I connected the overflow pipe from the barrels to a rain garden. This allowed the overflow, which was the majority of the roof water, to passively irrigate my lower garden without much work on my part. I can still use the water in the barrels to water my potted plants with a watering can, but I can also open the spigot of my rain barrels on a dry day and allow that water to irrigate the rain garden, and by proxy, my crops.

Incorporating some of these passive irrigation techniques into your backyard garden design may be all you need to keep your garden successfully irrigated. At the very least, they can help to reduce the size and complexity of an irrigation system.

Backup Drip Irrigation

It’s always a wise decision to have a backup for your irrigation solutions, as there may be times when mulching and passive irrigation aren’t enough. In this case, a drip irrigation system may be the right fit for your garden. This type of system delivers water directly to plant roots through a system of tubing, valves and emitters.

Watering the roots directly minimizes evaporation, in turn, minimizing the amount of water needed to irrigate. (It’s efficient!) Because the system avoids watering plant leaves, it also minimizes the potential for disease.

There are many drip-irrigation companies that can design a system most appropriate for your situation, but you can also find DIY starter kits that include all of the necessary components to get started on your own.

Be sure to place emitters and tubing between plants to encourage roots to grow outward toward the water source, strengthening them and making the plants more resilient. Conversely, running the tubing alongside plant stems will encourage roots to be lazy.

Watering a backyard garden through passive irrigation techniques will reduce cost and effort, while drip irrigation can be an efficient back-up that makes watering from municipal sources more efficient.

What types of irrigation solutions do you use in your backyard garden?

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