LOS ANGELES - Monsanto Co. (NYSE:MON - news) has asked a San Francisco federal court to allow it to continue selling its genetically modified Roundup Ready Alfalfa while the USDA conducts a court-ordered environmental impact study.

Monsanto, its seed distributors and growers stand to lose up to $250 million if the alfalfa, which was designed to survive the company's Roundup herbicide, is taken off the market for the two years it takes to complete the study, the company said in court papers filed late on Friday.

Earlier this month, U.S. District Judge Charles Breyer halted the sale of the modified alfalfa at the request of farmers, environmentalists and consumer advocates who say that it could harm the U.S. economy and the environment.

The judge voided the U.S. Department of Agriculture's 2005 approval of Roundup Ready Alfalfa, finding the agency had not conducted a full environmental impact statement. Breyer banned seed sales and gave farmers until March 30 to plant seeds they had already purchased.

Judge Breyer has set a hearing for April 27 to consider the plaintiffs' request for a permanent injunction.

Alfalfa, a fodder crop pollinated by bees and wind, is among the most widely grown crops in the United States, along with corn, soybeans and wheat.

In its brief, Monsanto presented testimony from scientists who said there was an "extremely low" risk that Roundup Ready Alfalfa would pollinate conventional crops if "appropriate stewardship measures" were taken.

Those measures include making sure that Roundup Ready crops are grown as much as 3 miles away from conventional crops to prevent cross-pollination.

Monsanto argued that a continued ban on Roundup Ready seed would force farmers "to plant lower-yield alfalfa breeds that pose more complicated and costly weed control problems, and require the use of more toxic or environmentally problematic herbicides."

The Center for Food Safety, which is among the groups that sought the injunction, said Breyer's order marks the first time a federal court has overturned a USDA approval of a biotech seed and halted planting.

The Center and other plaintiffs have argued that the biotech alfalfa could create super weeds resistant to herbicides, cause farmers to lose export business and contaminate natural and organic alfalfa.

They also alleged that Monsanto could try to force farmers whose crops were contaminated with Roundup Ready Alfalfa to pay for the company's patented gene technology whether they wanted it or not.