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New Mexico State University

New Mexico State University

News Center

Water-Holding Gel and Plastic Mulch Conserve Moisture in Gardens and Farm Crops

LAS CRUCES--Limited rain and snowfall in watershed ares of New Mexico this year may result in a water shortage for farmers and gardeners. Laser leveling fields and using drip irrigation help conserve water, but new techniques are needed to actually store water in the soil during periods of drought.

"Most rainfall occurs in New Mexico during the summer and fall," said George Dickerson, horticulture specialist with New Mexico State University's Cooperative Extension Service. "Much of this moisture is lost to evaporation, runoff or percolation down through the soil profile." Mulches and synthetic, water-absorbing polymer crystals can be used to store water around plant roots.

"The polymer crystals look like rock salt when they're dry," Dickerson said. "When exposed to water, the crystals swell to the size of marbles with a consistency of clear gelatin."

Research has shown that the crystals can absorb as much as 400 times their weight in water. When mixed in the soil, the polymers act as a reservoir, returning up to 95 percent of stored water to growing plants.

Dickerson and several county Extension agents have been working with farmers throughout New Mexico to evaluate the effectiveness of producing vegetable crops under semi-dryland conditions. Results have been impressive with polymer crystals and woven plastic mulch to control weeds.

"In most cases, we've only irrigated once or twice early in the season to get the transplants started," Dickerson said. "Thereafter, most of the plots received only natural precipitation."

Most sites produced excellent crops of chile and tomatoes. Dickerson estimates water savings was 63-93 percent over untreated plots.

"Last year, test plots with water holding crystals polypropylene mulch produced more than eight times as many bell peppers as untreated plots on the Ricky Parker Farm in Edgewood, near Albuquerque," he said. "Most of the plants in the untreated plots died from drought."

Dickerson says that the biggest effect on water savings probably comes from the plastic mulch. "The woven fibers of the mulch allow water and air to penetrate the soil. The tight weave, however, excludes sunlight, controlling weed growth and evaporation."

An ultraviolet light inhibitor in the mulch helps extend its useful life, so it can be used several years before replacing. The mulch also helps warm the soil early in the season to promote growth, Dickerson said.