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New Mexico State University

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Alfalfa Growers Push Production Limits, Hurt Reseeding Efforts

LAS CRUCES - Alfalfa is New Mexico's Tyrannosaurus rex of cash crops, a million ton shovel-headed meat eater with a mouthful of teeth. Valued at $161 million, it easily takes a bite out of the state's higher profile crops like chile, pecans and cotton.

NMSU agronomist Denise McWilliams says some New Mexico growers are pushing alfalfa's production to the limit, leaving some ancient stands in the field in southern New Mexico for more than two decades. (04/11/2002) NMSU agricultural communications photo by Norman Martin

But new research suggests that many of New Mexico's producers are pushing production boundaries to dino-rific proportions, in some cases extending a single planting's life span to more than 15 years. Indeed, says New Mexico State University agronomist Denise McWilliams, there are several ancient alfalfa fields in southern New Mexico that are "more than two decades old." Maintaining fields for more than five to seven years in other parts of the United States is remarkable.

These tough, old remnants present farmers with a difficult set of business decisions as planting time nears. Even though a single crop can easily produce upwards of six annual cuttings in some areas, alfalfa seed is considered so expensive that many producers try to cut corners.

Good quality seed is generally more than $60 an acre. With planting costs and establishment, costs can escalate to $200 to $300 per acre. The result: producers push production beyond recommended limits and try to reseed as gaps periodically appear. It's a plan that won't work.

"Once we have an established stand, it's very, very difficult to go back and reestablish spots within a stand," McWilliams said. "A lot of times we talk about a two-year rotation before we go back into an old alfalfa field."

The situation is further confused, experts say, because with each passing year the plants build up potent defense mechanisms that limit planting and reseeding options. Even reseeding occasional blank spots in new stands is tough because established plants crowd them out. "They compete very effectively for moisture and sunlight," McWilliams said. "Newly emerging seedlings just can't compete."

Alfalfa is New Mexico's leading cash crop largely because of a Swiss-army-knife versatility for growing in just about any of the state's widely different climate zones. More than half of the state's 270,000 acres are planted in just four counties - Chaves, Dona Ana, Eddy and San Juan. Still, a stunning mix of farming communities from the sweltering south to the high, cool mountain regions of the north contribute to the total.

"We pretty much use the spectrum of maturities and winter dormancies of major alfalfa varieties that are available in the United States," McWilliams said.

According to the New Mexico Agricultural Statistics Service, the state's growers produced 1.35 million tons of alfalfa last year. One reason for the plant's versatility lies in its
ability to find water. "It has very deep roots, usually more than four to five feet in depth, so it can really scavenge for water," she said.

Alfalfa first originated in Asia before 700 B.C., and is thought to have been first cultivated in Iran. The oldest cultivated forage crop in the United States, it is also one of the most nutritious. Rich in protein, vitamins, and minerals, the crop is prized as a primary component in dairy cattle rations and is an important feed for horses, beef cattle, sheep and goats. Alfalfa can be used as a pasture, hay or silage crop, in addition to being cut and dehydrated to make protein-rich livestock meal and pellets.

New Mexico has two alfalfa planting seasons. The smaller and usually more difficult of the two, the spring planting, begins in late March and April. The other major planting time is in September and October when soil moisture conditions are often better. Yet even with the best of planning and preparation, seeding gaps do pop up. And while there's a perfectly natural desire to fill in the holes, NMSU research suggests that it is better to stand back and let the gaps stay as they are.

If producers must reseed, they should disc or plow under any old alfalfa and reseed in the fall or the next spring. Once the seedlings are up, however, it is difficult to come back and fix any holes. Anything planted after six weeks to three months probably won't gain a toehold.

"Some of the problems we have with reseeding within established alfalfa crops are quite intense," McWilliams said. As alfalfa matures it produces a natural chemical as the forage breaks down in the soil. This auto-toxic reaction limits new plant growth.

She cautioned that it's never advisable to reseed to fill out an older stand. While the plants might look good early on, they may die out because of competition for light and moisture. A stand two years or older may also have enough autotoxicity that a farmer simply won't get a good establishment in reseeded spots.

To capitalize on alfalfa's potential, Ian Ray, an experienced alfalfa breeder and an associate professor of agronomy at NMSU, advises choosing high-yielding varieties with resistance to problem diseases and adequate winter hardiness. Historically, alfalfa producers have been encouraged to select new varieties based on results from NMSU variety trials conducted at agricultural science centers at Alcalde, Artesia, Farmington, Las Cruces, Los Lunas and Tucumcari, he said.

Alfalfa variety trial results are available in a NMSU's College of Agriculture and Home Economics publication called Guide A-135 or on the World Wide Web at http://cahe.nmsu.edu/pubs/_a/a-135.html.

"Only varieties that have been tested in trials over multiple years should be considered because this reflects stand persistence, fall dormancy and pest resistance," Ray said.