Adoption of genetically engineered alfalfa among farmers has lagged behind other biotech crops, with the vast majority of U.S. acreage remaining conventional, according to USDA.

Only about 13.5 percent of harvested U.S. alfalfa acreage is genetically modified, compared to more than 90 percent of corn, soybeans, cotton, canola and sugar beets acres, according to a new USDA report that cites 2013 farmer surveys.

It appears likely the percentage of genetically engineered alfalfa will continue rising, though: Roughly one-third of newly seeded acreage planted that year was of a biotech variety resistant to glyphosate herbicides, USDA said.

Farmers have been slower to adopt genetically engineered alfalfa partly because it’s a perennial crop that stays in the ground for roughly five years, said Dan Putnam, an alfalfa extension specialist at the University of California-Davis.

Cultivars can be shifted more quickly with annual crops, he said. “You can change your mind next year and do something completely different than this year.”

Commercialization of genetically modified alfalfa experienced a substantial setback after initially being deregulated by USDA in 2005.

Two years later, a federal judge blocked new plantings of a “Roundup Ready” glyphosate-resistant variety developed by Forage Genetics International and Monsanto.

The USDA took several years to complete court-ordered environmental analysis of the crop, which was again deregulated in 2011.

Genetically engineered sugar beets also encountered legal problems during commercialization, but adoption has nonetheless shot up to about 99 percent of planted acreage, according to USDA.

Alfalfa has particularities that have hindered greater adoption of genetically modified varieties, Putnam said.

In the Midwest and Northeast, farmers commonly plant a mixture of alfalfa, grass and clover for hay and forage, since each crop performs differently in fields with varying drainage conditions, he said.

“Using Roundup Ready doesn’t make any sense in that situation,” since glyphosate would kill the grass and clover, Putnam said.

Adoption of genetically engineered alfalfa is highest in Western states, where fields are generally devoted specifically to that crop and biotech cultivars comprise up to 60 percent of newly planted acreage in some areas, Putnam said.

However, fear of export market repercussions has quelled enthusiasm for genetically engineered alfalfa among some farmers, he said.

In California’s Imperial Valley, Monsanto and Forage Genetics have disallowed planting of biotech varieties in contracts with growers at the urging of local farm groups.

Alfalfa is often grown for seed in the Imperial Valley, particularly non-dormant varieties that are exported to countries with hot climates, such as Saudi Arabia, Mexico and South Africa, said Putnam.

Exporters fear that gene flow between conventional and biotech alfalfa will lead to rejection of shipments in foreign markets, he said.

“The export industry is very sensitive to the presence of genetically engineered crops,” Putnam said.

Forage Genetics International, which bought the rights to the crop from Monsanto, did not respond to requests for comment from Capital Press.

The Center for Food Safety, a nonprofit group that challenged the commercialization of genetically engineered alfalfa in court, isn’t surprised the crop hasn’t been adopted more widely, said Bill Freese, its science policy analyst.

Alfalfa grows so thickly that it suppresses weeds, so herbicides were seldom used on the crop before the biotech varieties were introduced, Freese said.

Despite the comparatively low adoption rate, Freese said his group’s concerns about genetically engineered alfalfa were not overblown.

Even though it’s not as pervasive as other biotech crops, genetically modified alfalfa nonetheless poses a risk for conventional and organic farmers where it is grown, he said.

The Roundup Ready crop also perpetuates the problem of weeds becoming increasingly tolerant of glyphosate, Freese said. In other crops, this phenomenon has led biotech developers to create varieties resistant to 2,4-D and dicamba herbicides.

“I wouldn’t be surprised to see that same pattern develop in alfalfa,” he said.