Wheat Benefits from Chloride

There’s no sure thing when it comes to improving wheat yields.

Research shows, however, that a narrow region of the Wheat Belt stretching from Oklahoma to South Dakota often gets immediate payback with a small dose of chloride. After 16 years, research by Kansas State University (KSU) shows that a 10-pounds-per-acre application of chloride improved yields by 3 bushels per acre over nontreated plots. That occurs when soil chloride levels are less than six parts per million, or 45 pounds soil chloride per acre. Older KSU research shows an 8-bushel-per-acre yield increase on sites that had soil chloride levels of less than 20 pounds per acre. 

South Dakota State University research from 2002 shows a 3-bushel-per-acre response to chloride application on three varieties. A soil test from that east-central South Dakota research site showed soil chloride levels at just 8 pounds per acre.

Chloride plays many roles in plant metabolism, including water regulation in cells and plant enzyme activation. It is an essential element in plant growth and photosynthesis. The positive effects from chloride are mainly seen in improved plant health, according to Dave Mengel, KSU soil fertility specialist.

In wheat, chloride deficiency shows up as physiological leaf spotting, or “random” chlorotic leaf spots, Mengel says. These spots are often mistaken for leaf rust or even tan spot, although chloride deficiency does not have the same halo surrounding the lesion, which is indicative of tan spot.

Be sure you need it
Blanket applications of chloride aren’t recommended, simply because many wheat-producing regions of the U.S. have enough soil chloride already. Generally, farms east of U.S. Highway 183 and west of Highway 77 from Oklahoma to South Dakota, with no history of potash application, may show low soil chloride levels and could benefit from application. Soils in the western regions of these states were the floor of an underground sea at one point, and the saltwater of these seas was loaded with chloride, Mengel says.

Ideally, producers have taken a 24-inch soil sample and test prior to planting the wheat crop. If so, the test will indicate whether the crop needs chloride. When 24-inch soil profile tests show between 30 and 45 pounds of chloride per acre, a 10-pound application is suggested. Below 30 pounds per acre requires 20 pounds, Mengel says.

If soil tests for chloride were not taken, take a plant-tissue test after wheat greens up in the spring to tell whether the wheat is deficient in chloride.

Producers may apply chloride during topdress fertilizer applications. It is available in dry form as potassium chloride (KCl) or liquid as ammonium chloride (NH4Cl). Most chloride applications cost between $10 and $20 per acre, depending on how much is required to bring levels up.

Impact on other crops
Farmers with low soil chlorine levels may also see benefits to chloride applications on other crops, based on additional KSU research.

Researchers performed 23 field trials from 1996 to 2006; 19 sites averaged a 10-bushel-per-acre yield increase when 20 pounds of KCl was applied compared with no application. There was no difference in the effectiveness between potassium chloride (KCl), sodium chloride (NaCl), calcium chloride (CaCl2), and ammonium chloride (NH4Cl).

A 40-pound application of chloride gave just a 1-bushel-per-acre yield gain over 20 pounds, Mengel notes.

In corn, the effects are less noticeable. Six of 11 research sites showed a significant response to 20-pound-per-acre chloride applications between 1996 and 2001.

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