What’s the Best Underground Irrigation Method?

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Photo by Flickr/Steveilott

Question: Which timesaving irrigation methods will get water right to plants’ roots without watering the weeds? — Russell Mullin

David Bainbridge: For small plots and container plants, buried ceramic irrigation systems, such as ollas, buried clay pots, porous clay pipes, and porous capsules, are some of the best watering methods. These allow you to put fertilizer and compost directly where the crops will absorb them. Water moves through the clay walls at a rate based on the plants’ water demands, so weeds have little to grow on, and the dry, open soil between plants will support fewer weeds. In areas with little summer rain, the difference can be striking. Think of the hours — potentially days — saved hoeing and pulling weeds. Adding heavy mulch between plants will further reduce your weeding time. 

Just a couple of years ago, few of these porous clay pot systems were available. Now, there are all kinds of olla suppliers. You can also use standard porous terra-cotta pots and plug the drainage holes with rubber stoppers, epoxy, or hot glue. Cover the top of the buried pot with a plate from a thrift store or a pot base, and drill a small hole in the lid to let rainwater in.

An even more efficient solution is wick irrigation, which relies on a fiber wick to transfer water to soil. As the plant soaks up water, it draws up more from the reservoir through the nylon or polyester wick. Wicks have long been used for growing African violets, because these flowers are so sensitive to water on their leaves. When growing smaller plants, you may only need to refill the wick reservoir every week or two. Wick irrigation works well for hanging baskets and window boxes; these setups are known commercially as “wickinators.” 

For larger shrubs and trees, I recommend using deep pipe irrigation. This method utilizes an open vertical, or nearly vertical, pipe to deliver water to the root zone, which leads to even deeper watering and excellent root growth, while minimizing weed growth. The pipe can be plastic, metal, or bamboo with the nodes drilled or knocked out. A commercial model called Deep Drip is now available at most home supply centers.

Few comparison studies have been done, but my own work has shown that watering with ollas, wicks, and deep pipes will make watering much easier, not to mention they helped my garden yield four times as many tomatoes as I’d been able to grow previously. Because you’ll likely need to refill them only once a week, these systems are ideal for busy gardeners who can’t get to their gardens until the weekend. Try a comparison in your garden this year!

David Bainbridge is a former professor of sustainable management at Alliant International University, and has used innovative irrigation systems for over 30 years. He’s the author of Gardening with Less Water.

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Mother Earth Gardener
Mother Earth Gardener
Expert advice on all aspects of growing.