Chloride

Soil Management

Adding Chloride Improves Plant Health and Crop Yield

eKonomics News Team

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Chloride is an essential nutrient many growers overlook. Chloride assists with a plant’s uptake of other soil nutrients and regulates the water flow through a plant. Chloride is critical for crop growth and photosynthesis. Wheat and other cereal grains are particularly sensitive to chloride deficiency. 

Chloride is typically abundant in soils in coastal regions or where farmers regularly invest in potassium fertilization, but soil chloride is often below critical levels throughout the U.S. Great Plains and Canadian Prairies. One of the most common potassium fertilizers, KCl or muriate of potash, contains potassium and chloride. Soils in the plains regions have historically contained high or very high potassium levels, so farmers apply little or no potassium fertilizer. Potassium application has traditionally not been necessary – so much so that retailers in western Kansas, for example, do not stock KCl fertilizer, says Dorivar Ruiz Diaz, a professor of soil fertility and nutrient management at Kansas State University.

“Growers think of KCl as a potassium source,” says Ruiz Diaz. “And they decide ‘I don’t need potassium,’ when in reality, application of KCl is the most cost-effective way to apply chloride.”

Soil levels by location

Chloride levels vary depending on location.

  • In eastern and southern states – especially coastal regions – chloride soil levels are naturally adequate due to atmospheric deposition.
  • In the Corn Belt and Great Plains chloride deposition is minimal. These areas are far from oceans, and there’s enough rainfall for highly mobile chloride to leach from the soil.
  • In Kansas, Nebraska, North Dakota, and South Dakota, more than half of soil samples tested had critically low levels of chloride.

Why chloride matters

Recent research indicates that chloride is as important as potassium for stalk strength. Low chloride levels can diminish crop yield by as much as 15 percent, Ruiz Diaz says, noting that there is a complex relationship between chloride soil levels and plant health.

Chloride influences how plants grow and helps enable greater disease resistance, especially foliar diseases caused by fungi in winter wheat, corn, grain sorghum and other crops. Kansas averages about 10 percent sorghum yield losses to disease annually, so KCl application can help boost yields and increase revenue. Farmers can also avoid related costs for fungicide and other products used to reduce disease impact on crops.

Identifying deficiencies

Chloride is essential to plant health but deficiencies are difficult to identify. Deficiency indicators include random chlorotic spots on leaves and are easily confused with the symptoms of fungal diseases. When caused by chloride deficiency, the symptom is called “physiological leaf spot.”  Some wheat varieties exhibit this characteristic spotting, while other varieties show no leaf spotting, even though growth may still be limited by chloride deficiency,

Annual soil sampling before the growing season is the most accurate way to determine chloride deficiency. Ruiz Diaz recommends that all fertilizer investment decisions be based on soil test results.

Chloride is highly mobile in soils so pull soil samples from 24 inches because plant roots can reach that depth in Great Plains soils. Rainfall can leach chloride so it’s important to know how much of the nutrient is available deep within the soil profile.

Adding chloride to increase yields

Experiments have shown that when soils contain less than 45 pounds of chloride per acre, yield responses to chloride application are likely. That’s why Kansas State researchers recommend chloride application of as little as 10 to 20 pounds per acre, depending on what the soil test levels reveal.

“Application rates do not have to be high to contribute to significant yield increases in deficient soils. Growers can expect a response to chloride fertilization of at least five to 10 bushels per acre,” Ruiz Diaz says.

Application options

Chloride can be applied at any point in the growing season. Applications in the winter and spring are equally effective. And chloride can be administered before planting, as starter fertilizer with planting, or with side dress methods after planting and before plants begin to grow. Liquid chloride sources work well but tend to be more expensive. Applying dry KCl fertilizer is the most common option in most regions, and creates what Ruiz Diaz calls a win-win scenario by making both potassium and chloride available to crops.

“KCl application is okay even in fields with high potassium soil test levels,” Ruiz Diaz says. “Potassium is a main nutrient that doesn’t leach from the soil. It’s not going anywhere, so when growers apply it with chloride, the potassium may not be needed this season but will be of value to crops in the future.”

When to invest in fertilizer

To optimize yields, pull soil samples and test for chloride levels before every growing season for corn, sorghum, and winter wheat in the Corn Belt and the Great Plains states. This testing is crucial in areas where KCl fertilizer has not been applied consistently.

Potassium levels should be determined by separate soil sampling on a schedule recommended by regional university agronomists or local certified crop advisers. Potassium levels have been declining below critical levels across the U.S., so it’s likely that farmers can address both low potassium and chloride soil levels with investment in KCl fertilizer. Consult with an agronomist or certified crop adviser for advice on fertilization rates based on your potassium and chloride soil test level results.

Learn more

North American soils are losing valuable nutrients at an alarming rate. Find out if the soil in your area has low levels of potassium and phosphorus on this North American map.

IPNI (International Plant Nutrition Institute), “Soil Test Levels in North America in 2015,” http://soiltest.ipni.net/ (accessed February 21, 2019).

K-State Research and Extension, “Kansas Sorghum Management 2019,” Kansas State University Agricultural Experiment Station and Cooperative Extension Service, January 2019, https://www.bookstore.ksre.ksu.edu/pubs/MF3046.pdf (accessed February 21, 2019).