Agronomy: New Trait in Soybeans: Chloride Exclusion

Next time you read a soybean seed catalog and check variety characteristics you might see a new trait listed—chloride excluder.

An Illinois farmer and ISA director emailed me and asked what chloride exclusion meant. He said he planted Syngenta’s NK 32-L8 variety and the product guide listed it as a “chloride excluder with dependable stress tolerance.”

Phil Krieg, agronomic service representative with Syngenta, said “The chloride excluder characteristic is helpful in areas where soil salts are higher, similar to what we sometimes experience in Southern Illinois. It presents no disadvantage to the variety, just an added benefit.”

I have never seen this chloride exclusion trait listed for soybeans during my career as an agronomist so it came as a surprise to me. However, across most of the Corn Belt we don’t deal with salty irrigation water or saline soils. Both chloride and sodium soil test levels are very low, as is the contribution for potash (potassium chloride), so we don’t give it another thought.

So why do we need a chloride exclusion trait? Dale Blevins, retired soybean agronomist and University of Missouri professor emeritus, said “This trait is usually mentioned when talking about salt tolerant plants. After taking up lots of sodium chloride salt, some plants have the ability to ‘extrude’ or secrete the chloride back out of their root cells and into the soil. This helps them tolerate high salt levels.”

So what is chloride exclusion? Emerson Nafziger, University of Illinois crop scientist, said the term refers to what happens to chloride when it comes into the root. “Excluders can keep it, or at least most of it, sequestered in the root and out of the xylem stream, while Includers let it in and it moves to the leaves where it causes damage.”

Salinity is mostly an issue for growers who irrigate with water containing salt, or who deal with saline soils. Nafziger explained that the chloride exclusion trait gets more attention in the mid-south, south and southeast. “In those regions breeders screen soybean varieties to see which are damaged by salt. Genes responsible for tolerance have been identified. Several late-maturing (MG 6+) varieties grown in the south have tolerance, including Hartwig. It doesn’t look like a lot of earlier MG varieties have tolerance, but they also aren’t exposed to enough salt to have a problem as few fields are irrigated and irrigation water isn’t salty in most irrigated areas in the Corn Belt.”

So next time you look at a soybean seed guide and see a variety has a chloride exclusion trait, be grateful you don’t have to deal with saline soils or salty irrigation water and can depend on nature’s rainfall and salt-free Illinois soil.

Agronomist Daniel Davidson, Ph.D., posts blogs on agronomy-related topics. Feel free to contact him at djdavidson@agwrite.com or ring him at 402-649-5919.