Issue: June 2002

Fight Drought with Drip Irrigation and Mulch

June is one of the year's driest months, and with a major drought gripping New Mexico, home gardeners need to find ways to conserve water.

Efficient irrigation is essential for water-wise gardens. Flood, furrow, sprinkler and drip irrigation are the most common watering techniques, but the first three are notoriously inefficient. With flood or furrow irrigation, most water moves down through the soil past the roots. Sprinkler water can evaporate or simply blow away.

In contrast, drip irrigation slowly delivers water to plant roots. The root zone remains moist but rarely waterlogged, creating a balance of water and air around roots for optimum growth. It also reduces root stress from flooding and drying cycles.

Studies show that drip irrigation can save up to 70 percent of applied water compared with a sprinkler system. Weeds are also reduced since water targets the root zone rather than aisles between rows. In addition, given that nutrients concentrate where water is, drip will help conserve nutrients because the root zone retains more water than with other irrigation systems.

To conserve more water, cover drip lines and areas around plants with mulch such as dry grass clippings, straw, hay or compost. Mulches help conserve moisture by reducing evaporation.

Mulch has other advantages, such as controlling annual weeds. Mulch shades soil and prevents weeds from germinating, but remove all weed seed from mulch before applying it.

In colder regions, black plastic mulch also helps warm soil. And most organic mulches tend to slowly decompose where they touch soil, releasing nutrients for plants.

Backyard drip irrigation systems vary from soaker hoses that ooze water out of multiple holes to tubing with individual emitters. Soaker hoses are easiest to use, but they tend to kink in tight areas, and water distribution is uneven. Tubing with individual emitters tends to distribute water more evenly. Place emitters 6 to 12 inches apart. Six inches is the best spacing in sandier soils.

Emitter lines are normally hooked to a supply line at least half an inch in diameter that connects to a faucet outside the house. Connect supply lines and soaker hoses to a preset pressure regulator with 15 to 30 pounds per square inch, plus a filter system to keep emitters clean and an antisiphon vacuum breaker to keep water from siphoning back into household water lines. The anti-siphon device connects directly to the faucet, but must be at least 6 inches above all the emitters in the drip line. For maximum control, connect the antisiphon device to a battery timer to regulate when and how long the system remains on. The battery timer can be directly connected to the faucet and the faucet left on, but with this system, the antisiphon device must be below or "downstream" from the timer to be effective.

For more gardening information, visit New Mexico State University's Cooperative Extension Service publications World Wide Web site at http://pubs.nmsu.edu/_h

Also Please join us on Southwest Yard & Garden, a weekly garden program made for gardeners in the Southwest on: KNME-TV Albuquerque at 9:30 p.m. Saturdays, KENW-TV Portales at 10 a.m. Saturdays,and KRWG-TV Las Cruces at 11:30 a.m. Saturdays (repeated at 1 p.m. Thursdays.)

George W. Dickerson, Ph.D., is is a horticulturist with New Mexico State University's Cooperative Extension Service. New Mexico State University is an equal opportunity/affirmative action employer and educator.