A drip irrigation system delivers water directly to the root zone of a plant, where it seeps slowly into the soil one drop at a time. Almost no water is lost through surface runoff or evaporation, and soil particles have plenty of opportunity to absorb and hold water for plants. It also means very few nutrients leach down beyond the reach of plant roots. Furthermore, since drip irrigation delivers water directly to the plants you want to grow, less is wasted on weeds. The soil surface between the plants also remains drier, which discourages weed seeds from sprouting.
For busy gardeners, the main benefit of drip irrigation is the savings of both time and effort. Drip systems eliminate the need to drag around hoses and sprinklers. For systems that use a timer, gardeners need only spend a few seconds to turn the system on; the timer automatically turns it off
Plants watered with drip systems grow more quickly and are more productive, because they have all the water they need and their growth isn’t slowed by water stress. (This is especially true when drip irrigation is used in conjunction with mulch.) Also, plants watered by drip irrigation don’t end up with wet foliage from a sprinkler spray, and that can help prevent some foliage diseases such as powdery mildew.
Start with Soaker Hoses
The easiest way to experiment with drip irrigation is to buy a couple of soaker hoses. These hoses ooze water over their entire length. You simply position a soaker on the soil surface next to the plants you want to water, and then connect the open end of the hose to your garden hose and turn on the water supply. You can move the hose from one bed to another in your garden, or buy several and leave them in place. Soaker hoses can be used for short runs (100 to 200 feet) over flat surfaces.
photo: (cc) ryo chijiiwa/flickr
Soaker hoses are great for row crops such as carrots and beans, but for watering trees and shrubs or a series of containers, you’ll probably want to set up a more sophisticated system. Drip irrigation systems move water at low pressure through a series of tubes and other hardware and deliver it to precise locations and specific plants of the gardener’s choosing. Although each system is different, water generally flows out of your faucet through a timer (which is optional), a filter, a pressure regulator, and into a series of hoses or pipes that carry water to emitters, which are small devices that release water drop by drop to the plants. Some systems use drip tape—flattened plastic hoses with holes at regular intervals. A complex system may contain two or more individual lines as well as valves that allow for watering specific parts of the garden.
Designing a System
The first step in designing a drip irrigation system is deciding what you want the system to 203water. Is it only for your vegetable garden, or will you use drip irrigation for your entire landscape? Topography is also a consideration: If your garden is hilly, you’ll probably need to use emitters that compensate for pressure changes in the line.
Keep in mind that plants can become “addicted” to drip irrigation, because roots will concentrate in the area where the water is available. When designing a drip system to carry water along the rows of a vegetable garden or to the roots of a prized rhododendron, it’s important that the water be spread uniformly throughout the irrigated area so root growth will be uniform. For example, if you are irrigating larger plants such as trees and shrubs, place emitters on two or more sides of each plant to encourage roots to grow out in all directions rather than clustering on one side. For the same reason, it’s best to use your system to provide a long, slow watering. If you turn it on for frequent, short waterings, water won’t have a chance to spread far in the soil, and consequently the roots will form a tight, ball-like mass around the emitters.
You can design your own system, but most companies that sell drip irrigation equipment will design systems for you if provided with a scale drawing of your garden, information on what you’re growing, your soil type, and garden topography. Their design will come complete with a list of parts and spacing for emitters. Whatever method you choose, start by making a fairly accurate drawing of your garden to determine how many feet of tubing you’ll need.
If you’re designing your own system, consider asking a few gardening friends to adopt drip irrigation too. That way you can split the cost of the system components, which have a lower base cost when you buy large quantities such as 500-foot-long rolls of drip tape or sets of 100 emitters.
Kits for beginners. A low-risk way to get started with drip irrigation is to buy a starter kit. Most companies that sell drip irrigation systems also offer kits for both small and large gardens, which come with the essential components necessary to set up the system. Keep in mind that kits often don’t include parts such as pressure regulators, timers, backflow preventers, and line filters. Be sure to buy a kit that can be added onto, so you can expand your system over time.
photo: (cc) joby elliot/flickr