Seeding alfalfa in saline soils

Most western United States alfalfa growers are faced with salt issues in their soils.

But while soil salinity can alter good stand establishment and forage production, new varieties, along with management, can help producers combat the issue, said Don Miller, director of product development for Alforex Seeds.

“I’ve worked on salinity tolerance for a lot of years as an alfalfa breeder,” said Miller, adding the issue is one that is “near and dear to my heart.”

Determining the right soil problem is key, said Miller. Producers often confuse salinity, alkaline or alkali soils, using them interchangeably.

“But there are subtle differences between them,” he said.

Saline soils have elevated levels of dissolved salts with an electrical conductivity, or EC, greater than 4, he said.

Meanwhile, alkaline soils have a pH above 8.5 and alkali soils have sodium levels greater than 15 percent.

“Saline soil is defined as one with enough salt in the soil solution to interfere with the crop growth,” he said.

Every crop species has its threshold, he said. But alfalfa is more sensitive. Miller noted that in alfalfa an EC level of 3 can mean a 7.5 percent yield reduction. At an EC level of 4, it goes up to 15 percent.

“The bigger the EC number, the more yield loss we have.

Miller said salt is making its way to fields a variety of ways. Irrigation water can carry salt to the fields and rivers have certain levels of salt.

“It was quite startling to me how much salt is begin picked up by the water that is coming out of the ground,” Miller added.

The California aqueduct can carry 600 to 700 pounds of salt per acre foot of water applied. For irrigators, that could mean 1.2 tons of salt per acre a year after a full irrigation season.

“That is a tremendous amount of salt you have to deal with,” he said.

Colorado and the Dakotas have saline seeps where the water-table rises bring up salts.

“So, different parts of the country have different issues on how they have to deal with salinity,” Miller said. “But again, genetics out there are helping us.”

Miller said Alforex began researching to see if it could produce increased salt-tolerant varieties through plant selection.

“The breeding objective was, ‘can we, with the improved alfalfa lines, in these hotspots, can we reduce the hotspots and get more to germinate under this salt stress,’” Miller said.

Miller said you can improve genetics, but producers should look at the entire system and have an integrated approach to improving their fields and getting more production. That includes crop rotation, crop selection and crop species.

Different crops have different salt tolerance levels. Miller said to use a species tolerant to the level of salinity. As soil improves with integrated soil and water management, growers can move to higher value tolerant crops.

Also, he said, improved soil structure enhances the leaching of salts out of the root zone.

“Find out where you are at in the field,” Miller said. “Conduct a soil and water test to determine the exact severity of salinity.”

Alforex continues to work to improve its varieties, he said.

“We’ve made progress over the years and we are continually working on, pushing that envelope even higher,” he said.

Amy Bickel can be reached at 620-860-9433 or [email protected].