Some rice farmers can use much less water and get the same yield by flooding their fields at the start and end of the season, and letting them dry out a bit in between, Mississippi State University researchers say.
That's a radical change from recommendations across the Rice Belt to keep two to four inches of water in the fields, irrigation specialist Jason Krutz said in a news release. Instead, he recommends letting fields dry until water is 4 inches below the soil surface, then re-flooding them.
He said that can cut water use 30 percent without hurting yields.
MSU's tests were on high-clay soils, which probably make up about half of Mississippi rice fields, Krutz said in a telephone interview.
He says he believes Arkansas researchers will study its use in silt-loam soils like those in south Louisiana and parts of Arkansas.
The "alternate wetting and drying" or AWD technique saved an average of $50 a season across fields ranging from 20 to 80 acres, he said.
It saves more money in wet years than in dry years, agronomy graduate student Lee Atwill said.
"By allowing the fields to go dry to 4 inches deep, we're able to capture that rainfall when it happens," Atwill said in a news release. "In a continuous flood environment, we lose a lot of water to the tail ditch because it spills over since our paddies are already full."
Krutz said saving water doesn't just have an economic benefit. Mississippi is a state that regulates water usage, setting the amount allowed for rice at 36 acre-inches of water.
That amount is the state average, he said.
"That means 50 percent of the time, we're using more than what we're permitted to use," Krutz said. "That's why it's critical that we have a strategy that maintains and improves yield while reducing water use."
He estimated that about one in five Mississippi farmers uses some form of the technique.
Rice is planted and nitrogen applied before a field is flooded. It's kept flooded for 21 days, then allowed to dry for the next four to six weeks. Then the field is re-flooded for the two weeks when rice is flowering.