Nutrient of the Month – Chloride, Just Misunderstood

Written by Mike Hamilton, CCA & President of Turf Dietitian

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Chloride

For some reason, Chloride has gotten a bad name in the turf industry. Could it be, at some point in the past, a Superintendent over-applied chlorides and burned turf?

Alternatively, could it be as simple as the margins for chloride products being so low that few fertilizer distributors want to sell the product?

Regardless of the industry’s reluctance to use chlorides, if your soil test shows deficient levels of Chloride in soil solution, products like calcium and potassium chloride are the most efficient and effective sources to feed the turf a healthy diet.

If chlorides are as evil as some turf consultants claim, why is potassium chloride the most-used potassium fertilizer in the world? Is it because it’s the cheapest potassium source? No, it’s because potassium chloride is efficient and increases plant yields.

Chloride fertilizer sources aren’t for everyone.

Chloride is an essential micro-nutrient; a plant cannot survive without it. However, chlorides are not for everyone. High concentrations of Chloride can cause toxicity problems in turf and reduce turf quality. Toxicity results from the accumulation of Chloride in the leaves. If your course has a sufficient or excess amount of Chloride in soil solution and plant tissue, then using a chloride source will be ineffective and potentially toxic.

If your golf course is in a coastal region with a reclaimed supplemental water source, or you are in an area with sodic or saline soils, then most likely, chloride sources aren’t for you. However, don’t automatically rule out chlorides if your course falls into one of these categories. Since Chloride is an anion, it does not adsorb to soil particles. It moves readily with the water in the soil. Chloride can move so quickly through the sandy soil that it can become deficient with average rainfall, even on golf courses near the ocean.

Consequently, the only way to know for sure what the level of chlorides is in sandy soil is to test through all environmental conditions.

Uptake of Chlorides by plants.

All turf species and varieties differ in their chloride requirements and their tolerance to chloride toxicity. Still, typically most species of turfgrass have a high tolerance to Chloride.

Plants take up Chloride as Cl- ion from the soil solution. It plays crucial roles in plant processes, including photosynthesis, osmotic adjustment, and suppression of plant disease.

The primary roles of chlorides within the plant:

• Chloride is essential in the opening and closing of the stomata. Chloride and potassium are pulled into the plant when the stomates open at night.
• Chloride is essential to balance the potassium ion (K+) concentration that increases in the guard cells. Once the stomates close, pressure from chloride gas builds up in the guard cells. The guard cells open when the gas becomes abundant, starting the respiration and transpiration process.
• Chloride plays a primary role in splitting water in the photosynthesis process.
• Chloride is one of the nutrients responsible for transporting immobile nutrients through the plant and in cation balance within plant cells.
• Chloride diminishes the effects of fungal infections and suppresses disease outbreaks.
• Chloride applications reduce nitrate uptake, which promotes plant consumption of ammonium nitrogen. Lowering nitrate uptake may be a factor in Chloride’s role in disease suppression since high plant nitrates are usually associated with disease severity.
• Chloride regulates and promotes the activities of key enzymes.
• Chloride is a critical component in the development of plants.

Chloride, nitrate, sulfate, borate, and molybdate are all anions in their available forms, and in that form, they are antagonistic to each other. Therefore, an excess of one can decrease the availability of another.

Toxicity symptoms

Water quality and irrigation management are the major factors that affect chloride concentrations in soil.

• Common symptoms of chloride toxicity in plants include necrosis of leaf margins and tips, typically occurring in older leaves first.
• Excessive leaf burn might eventually result in leaf drop.
• Wilting due to a restricted and highly branched root system, often with stubby root tips.

Chloride Fertilization

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Application Information

Common chloride fertilizer sources:

• Potassium Chloride
• Calcium Chloride
• Magnesium Chloride
• Ammonium Chloride

Green and Tee Liquid Applications

On close-cut turf that receives weekly applications of liquid fertilizer, rates should be no higher than 12 lbs of commercial product per acre.

Fairway and Rough Granular Applications

In areas where deficiencies exist, 30 to 100 pounds per acre of Chloride per year will supply the needs of responsive turf. The response may be improved even further if the application gets split.

More facts about Chloride:

• Chloride fertilization has shown promise in suppressing several diseases.
• Chloride fertilization results in delayed leaf senescence. And a relatively greater leaf water content.
• Because Chloride doesn’t get absorbed by organic matter or clay and does not readily precipitate out of solution, it will leach with rainfall or heavy irrigation.
• A salt injury occurs when too much NaCl accumulates in the substrate. Also, water uptake can obstruct due to excessive concentrations of NaCl present in the soil.
• Chloride fertilizers are less expensive than other fertilizer sources because Chloride is 100% water-soluble. Much less product and water are typically needed to achieve the desired results.
• Chloride can be used as a soil amendment treatment to reduce sodium levels in the soil.
• Calcium chloride improves soil tilth and reduces crusting.