Kansas State University soil fertility specialist Dave Mengel suggests that adding chloride to a wheat topdressing blend could improve yields.
"More field testing is needed, particularly in western Kansas, to determine the extent of chloride-deficient areas in Kansas. But based on current data, the probability of a response to chloride in dryland wheat production in central Kansas is high," Mengel says in the Jan. 18 edition of Kansas State University's weekly Agronomy Update newsletter.
Due to chloride's propensity to leach in the soil, the only way to base the crop's need for chloride is with a 0-24-inch soil test, Mengel says. Most soil testing laboratories, including K-State's, offer a chloride soil test.
Most central and western Kansas oils are high in potassium. Therefore, use of potassium chloride fertilizer has been limited in the past, and these soils have a greater chance of low chloride levels than, say in eastern Kansas, where potassium chloride is routinely applied.
Chloride fertilizer is recommended when the soil test is below six parts per million, or 45 pounds soil chloride in the 24-inch sample depth. Potassium chloride (potash) and ammonium chloride are the most commonly available and widely-used products, although calcium, magnesium and sodium chloride may also be used.
Soil test interpretations for wheat, and recommended applications, include:
- less than 4 ppm (30 pounds per acre): 20 pounds chloride per acre recommended
- 4-6 ppm (30-45 pounds per acre): 10 pounds chloride per acre recommended
- More than 6 ppm (45 pounds per acre): 0 pounds chloride per acre recommended
Chloride helps with the transport and uptake of essential cations, such as calcium, potassium, magnesium and nitrate. The nutrient also helps the plant resist diseases such as leaf rust, tan spot, septoria and take-all.
Visual symptoms of chloride deficiency show up in some wheat varieties as spots on leaves similar in appearance to tan spot lesions (without the characteristic 'halo') and are called physiological leaf spot, Mengel says.
Of 39 studies from 1990-2006 primarily in eastern Kansas, 23 studies showed a statistically significant response to chloride fertilization. Treatments compared chloride application rate, source and time/method of application. Thirty-four experiments, which featured chloride fertilizer rates of 0, 10 and 20 pounds per acre, applied as potassium chloride in the spring, are summarized below.
Response of wheat to chloride fertilizer, 1990-2006
Chloride Application Rate (Pounds chloride per acre) Grain yield (bushels per acre) Percent Chloride
(in top leaves at boot)
0 48.4 0.29
10 51.7 0.38
20 52.5 0.43
LSD: 0.05 1.3 0.03
Source: K-State Agronomy