Researchers are testing nitrogen application timing on furrow-irrigated rice at the LSU AgCenter Northeast Research Station. LSU AgCenter photo.

LSU AgCenter researchers continue to study the benefits and challenges posed by the alternative rice growing method of planting rice on furrow-irrigated rows.

AgCenter extension rice specialist Ronnie Levy said in 2020 Louisiana rice growers produced about 480,000 acres of rice — 35,000 acres of which were grown on rows. While row rice tallied about 7.5% of the state’s total rice acreage, the burgeoning method constitutes about 30% of rice acreage in the northeast Louisiana region. For the 2021 growing season, researchers are seeing a 50% to 60% decline in those acreage numbers due to a delayed planting season caused by early precipitation and because of the market price of other commodities, such as soybeans and corn, competing for acreage across the state.

“The No. 1 invasive weed in row rice is $14 soybeans,” Donnie Miller, LSU AgCenter weed scientist, said.

Growing rice on rows aids farmers by allowing flexibility when choosing what to plant based on commodity market prices.

“The reason we plant row rice is because it makes you prepared to produce either rice, soybeans, corn or whatever is most profitable,” Levy said. “For some producers, it just made sense to make the switch to soybeans, especially in the northeast part of the state.”

Planting row rice was also hindered this year by early spring rains because planting rice on rows requires drill seeding, Levy explained.

Levy said the key to seeing the benefits of growing rice on furrow-irrigated rows is proper timing.

“You have to do everything on time,” Levy said. “If you get behind on fertility or weed control you never catch up. Timing is critical.”

Though most of the state’s row rice is grown in northeast Louisiana, agronomist Dustin Harrell, resident coordinator of LSU AgCenter’s H. Rouse Caffey Rice Research Station in Crowley, is conducting field trials of row rice on silt loam soil, which is found predominantly in south Louisiana. At the Northeast Research Station, heavy clay soils are dominant.

Of the many benefits of row rice is a reduction in water usage during the growing season. Harrell said some row rice growers have attested to using as much as a 35% less water than those who flood their entire crop. The water that irrigates row rice is applied via polypipe. When flooding fields, growers must move soil to make levees to retain the water. With row rice, that practice is not needed.

“One of the big benefits of row rice is farmers make fewer trips across the fields,” Harrell said. “So, we’re saving money on labor and diesel costs.”

Row rice does present some challenges for researchers. Disease-causing fungi, nitrogen intake losses and weed control are some of the hurdles that Harrell and other researchers are looking to clear. Flooding rice fields diminishes the spread of weeds, but growing row rice opens the door for nuisance vegetation. Row rice is also more susceptible to the plant pathogenic fungus known as blast because of changing water levels within the fields.

“When you grow rice in upland conditions, you make it susceptible to blast,” Harrell said. ”It’s very important that we use rice varieties and rice hybrids that have good blast resistance if you’re going to grow furrow-irrigated rice.”

Nitrogen-use efficiency is much lower in furrow-irrigated rice than is traditional rice fields. Harrell said the fluctuations from dry to wet conditions causes an increase in nitrogen-loss mechanisms. Research is currently being conducted to determine how much more nitrogen is needed in furrow-irrigated rice rather than flooded rice.

“We are trying to answer questions like ‘How do we apply nitrogen in furrow-irrigated rice?’” Harrell said. “Do we need to apply it like we do in our flooded fields, or do we need to spoon-feed it? And, if we spoon-feed it, how many applications do we need?”