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Salt Tolerant Traits in Southern States Soybeans

How can growers protect crops from high salt? Salt-tolerant Traits in Soybeans can be one solution.

High chlorine can negatively impact soybean yield performance. CL toxicity can occur from the salinity in irrigation water as well as certain soil types.

Salty Irrigation Water

In some areas of the South, high salt levels in irrigation water can cause big headaches for soybean farmers. Depending on the level of salinity, too much salt can reduce soybean yields or, in worst-case scenarios, wipe out an entire crop. 

In a growing crop, the chloride in salty water can stunt or kill young leaves. Farmers can identify salt damage by looking underneath the leaves between the veins, according to Southern States Seed Production Manager Jason Hinton. "You have interveinal chlorosis and necrosis, which you can see in the yellowing of the older leaves first," Hinton says. "These leaves can eventually die off, stunting the plant’s growth and diminishing its yield."

Our chloride toxicity experiences in Georgia, according to Eddie McGriff, Southern States Agronomist, relate more to a certain soil type (Atlantic Flatwoods soils). In the early 1980's, Extension agents observed a soybean leaf scorch problem on certain Atlantic Flatwoods soils in late season (R4-R6) in dry seasons.  After extensive leaf and soil sampling, Dr. John Woodruff, University of Georgia Extension soybean specialist, lead a team of scientists that concluded the problem was chlorine toxicity, and labeled the problem as "Soybean Leaf Scorch".  Myron Parker then began a comprehensive research study of the problem. 

Some of the conclusions from that study were:

  1. About half of the soybean varieties grown then did not get the problem (It was assumed that they had an excluder gene)
  2. The only noticeable problem occurred in low areas of fields (classified as Atlantic Flatwoods).  In sampling these areas, Mr. Parker found high levels of chlorine in the soil water.  These soils have an impervious natural hard pan about 5-6 feet deep.  Water from rain and or irrigation does not drain through this layer.  These soils would tend to be very wet in early spring, but productive in normal seasons.  In dry summer seasons, deep rooted plants (those not having the excluder gene) would accumulate toxic amounts of chlorine.
  3. In greenhouse studies, Mr. Parker was able to induce chlorine toxicity when potassium chloride was applied at high rates (enough to get chlorine level above 550 ppm).
  4. Soybean yield loss from leaf scorch ranged from 0 to 50 percent

The University of Georgia began screening all soybean varieties in the official variety trials.  Only varieties with the apparent excluder gene were recommended for planting on Atlantic Flatwoods soils.  Over time, the screening process stopped.

Dr. Woodruff does not believe that there is any problem with preplant potassium chloride fertilization on soils other than Atlantic Flatwoods soils, but because the chlorine toxicity problem can occur on non-cl excluder varieties, he is hesitant to encourage any potassium chloride sidedress application, especially after R1 growth stage.

The soybean leaf scorch problem was also reported on heavy clay soils in Arkansas.  Their research conclusions were the same as those of Mr. Parker.

Plant a tolerant variety

To help prevent damage from CL toxicity, soybean growers can start off the season protected with a salt-tolerant seed variety. Salt-tolerant varieties come equipped with a gene specific to handling excess amounts of sodium chloride. These varieties carry an excluder gene, which stores any extra chloride in the roots of the plant. "It keeps the excess chloride where it won’t hurt the soybean," Hinton says.

In contrast, varieties without the excluder gene send salts to the leaves. "The plant will store chloride in the upper part of the plant where leaves are growing," Hinton says.

While farmers in these areas should plan ahead with salt-tolerant varieties, keep in mind they are not a magic cure-all for salt damage, says Hinton. "Even with the excluder gene, if salt levels are too high, it can still be toxic to a plant."

Contact your Southern States Agronomy Professional for more information on the soybean varieties that best match the management practices and needs of your individual fields.

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