* U.S. lawmakers call for continued ban on biotech alfalfa

* Say USDA has "ignored" regulatory authority

* Say U.S. organic dairy industry threatened

* Related sugarbeet court case delayed

(Releads, Adds details, delay in sugarbeet case, Monsanto comments)

By Carey Gillam

KANSAS CITY, June 23 (Reuters) - More than 50 U.S. lawmakers are calling on the U.S. Agriculture Department to keep Monsanto's MON.N biotech alfalfa out of farm fields, despite a Supreme Court ruling this week that cleared the way for limited planting pending environmental reviews.

The lawmakers said the biotech alfalfa presents too great a risk to conventional and organic agriculture to ever allow it.

"We believe that the broad regulatory authority available to you has been ignored, in order to justify deregulation of a biotech crop that has limited utility to anyone except the manufacturer," the letter addressed to Agriculture Secretary Thomas Vilsack said.

U.S. Sen. Patrick Leahy, a Democrat from Vermont, and Rep. Peter DeFazio, a Democrat from Oregon, were joined by 49 other representatives and five other senators in asking Vilsack to ensure that Monsanto's genetically engineered alfalfa is not approved for commercial use.

The alfalfa, which has been altered to tolerate Monsanto's Roundup herbicide, and is known as "Roundup Ready" alfalfa, was approved by USDA in 2005 and was planted in limited quantities around the United States.

But environmental groups and some seed companies sued the USDA in 2006 and successfully forced the agency to rescind its approval after a federal court found USDA had violated environmental law by failing to do a thorough environmental review before approving the product.

That environmental impact statement still has not been completed, and USDA's Animal and Plant Health Inspection Service (APHIS) has said it expects to have one done by spring. But Monsanto said this week it wanted the agency to accelerate approval.

Still, the lawmakers' letter to Vilsack said that there is strong evidence the biotech alfalfa will contaminate conventional alfalfa fields, and could spell disaster for the organic dairy industry by contaminating the feed fed to organic dairy cows if USDA approves it. Organic forage would become harder to find and more expensive.

The lawmakers cited contaminations in several fields during the two years that the biotech alfalfa was grown commercially despite the fact that those conventional fields were far from the biotech fields.

Alfalfa is the fourth-largest U.S. field crop grown on about 23 million acres in the U.S. annually. It is pollinated largely by honey bees, making it difficult to isolate biotech alfalfa from conventional varieties.

The organic dairy industry, which has about $1.4 billion in annual sales, will suffer "significant economic losses" if the USDA approves the product.

Monsanto spokesman Garrett Kasper said there were many benefits to its biotech alfalfa and it wants to be able to start selling the seed soon.

"The farmer and environmental benefits of ag biotech are well established and farmers are anxious to have the choice to grow Roundup Ready alfalfa," said Kasper. "USDA has the expertise necessary to evaluate these products and we are hopeful that USDA will issue guidance, following the Supreme Court decision on Monday, which will allow farmers to resume planting Roundup Ready alfalfa this fall."

On Monday, the Supreme Court ruled that a district court judge in San Francisco had abused his discretion in barring the USDA from pursuing a partial deregulation and in prohibiting the planting of the biotech alfalfa seeds, pending the completion of an environmental review. [ID:nN21252613]

The ruling, however, did not alter the lower court decision that banned the biotech alfalfa until completion of a full environmental review.

A similar case involving Monsanto's biotech sugarbeets, was slated for a court hearing July 9, but the judge in that case has postponed the hearing until mid-August to give all parties a chance to study the Supreme Court ruling. The court has already ruled the sugarbeets were approved by USDA without proper environmental review and is considering a permanent injunction.

Andrew Kimbrell, executive director of the Center for Food Safety, one of the plaintiffs in the alfalfa lawsuit, said USDA needed to focus on the well being of U.S. consumers and agriculture, and not Monsanto.