Algae prevents rice from reaching stand

Some Arkansas farmers who water-seeded rice into fields that have been flooded since last fall for duck hunting have experienced problems getting the rice to produce a good stand, says Chuck Wilson, rice specialist with the University of Arkansas Cooperative Extension Service.

Wilson said the problem appears to be caused by algae growing in the water. The algal blooms deplete oxygen in the water, preventing rice seed from surviving.

Normally, rice seedlings take oxygen from the water until their leaves can emerge and start drawing oxygen from the air. The plants then pump oxygen down into the roots to help them survive a flooded environment, according to Wilson.

“I don't see this problem every year,” he said. He believes it's related to environmental conditions, especially cold weather.

The main reason farmers hold water on fields over the winter is to attract waterfowl. “For a lot of farmers, hunting leases are a big portion of their income,” Wilson said.

Wilson said farmers roll down the straw left in the fields after harvest, then they flood the fields. This attracts ducks, which eat white rice and the seed of red rice, which have been left in the field after harvest.

The flooding also helps control winter weeds and saves farmers from having to re-flood fields in the spring if they're going to water-seed. But Wilson discourages using this water for water-seeding.

“The point of water-seeding is to control red rice, a serious weed problem. That's one reason they don't want to drain the water, because it prevents weeds from coming up. The red rice seed in the soil won't germinate through the soil and water.

“Farmers are trying to conserve water for water-seeding, but using ‘winter water’ creates problems when certain conditions allow algae to thrive,” Wilson said.

“In one field I looked at, the farmer had a considerable amount of algae and rice stubble left in the field after last year's crop was harvested,” Wilson noted. “The farmer tried to water-seed it in the spring. Some of it sprouted, but it couldn't push through a thick algae mat on the surface. A large amount of seed simply died after sprouting because of a lack of oxygen. The farmer didn't have a good stand of rice.”

Wilson compared the problem to some bodies of water in northwest Arkansas where algae blooms have removed oxygen, killing fish.

Rice farmers in California have experienced similar problems and discontinued the practice of water-seeding into “winter water,” Wilson said. He said Arkansas farmers should drain winter water in late February or early March, dry out the fields thoroughly, then re-flood and seed into the fresh water.

Farmers who didn't plant rice by water-seeding, have experienced different weed control problems this spring. “It's been a challenging year, so far, to fight weeds.”

Meanwhile, Wilson said March estimates of a 1.42-million acre rice crop may be conservative. Since that figure was released by the Arkansas Agricultural Statistics Service, the futures price of rice has steadily risen over the last several weeks, which has probably spurred more planting, Wilson said.

Lamar James is an Extension communications specialist with the University of Arkansas.

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