What to Do When Crops Are Deficient in Chlorine? Symptom Identification and Correct Use of Chlorine-Containing Fertilizers

Chlorine is one of the essential elements for the growth and development of many crops. Many plants will grow poorly if they lack chlorine, so what should be done when crops are deficient in chlorine? What are the symptoms? How should chlorine-containing fertilizers be used? Let's take a look.

1. The role of chlorine in crops

1. Participation in photosynthesis. In photosynthesis, chlorine acts as a cofactor for manganese in the photolysis of water. The photolysis of water is the first photochemical reaction of photosynthesis.

2. Chlorine regulates the opening and closing of crop leaf stomata, thereby enhancing the drought resistance of plants. In addition, chlorine has the ability to bind water, which helps crops absorb more water from the soil.

3. Applying chlorine-containing fertilizers can inhibit the occurrence of many diseases. According to reports, for at least 10 crops, increasing the application of chlorine-containing fertilizers has significantly reduced the severity of disease. Examples include stripe rust of spring wheat, root rot of barley, and stalk rot of corn.

4. Chlorine is highly active and enters plants very easily, and it can promote the absorption of ammonium ions and potassium ions by plants.

2. Symptoms of chlorine deficiency in crops

The general symptoms of chlorine deficiency are stunted plants, chlorosis of leaves, and smaller leaf shape. The symptoms of chlorine deficiency are not exactly the same in different crops. For example, spring wheat with chlorine deficiency shows yellowing leaves and many spots; lettuce, cabbage, and alfalfa with chlorine deficiency show wilted leaves, but the roots are thick and short, club-shaped, and the edges of young leaves curl upward in a cup shape; when cotton is deficient in chlorine, the leaves wilt, the leaf color is dark green, and in severe cases the leaf edges dry up and curl.

3. What to do when crops are deficient in chlorine?

Because chlorine has a wide range of sources, the chlorine contained in the atmosphere and rainwater alone far exceeds the annual requirement of crops, so chlorine deficiency rarely occurs under field production conditions. Once chlorine deficiency occurs, applying chlorine-containing fertilizers such as ammonium chloride and potassium chloride can eliminate the symptoms.

4. How should chlorine-containing fertilizers be used?

1. Avoid using them on sensitive crops and during sensitive periods of crops: Different crops and varieties differ greatly in their sensitivity to and tolerance of chlorine. Crops sensitive to chlorine are called chlorine-avoiding crops, including tobacco, tea, citrus, grapes, watermelon, potato, Chinese milk vetch, and so on; generally, chlorine-containing fertilizers are not applied to them, or the application rate is strictly controlled.

2. Pay attention to the application method of chlorine-containing fertilizers: When using chlorine-containing fertilizers as a base fertilizer, apply them deeply and early and cover with soil, generally one week before sowing or transplanting, and apply them below the seeds or seedlings, preferably at a depth of 5~7 cm from the topsoil. When used as a topdressing: adopt hole application or band application, and keep a distance of 5~10 cm from the crop plants; never broadcast them.

3. Apply chlorine-containing fertilizers as much as possible in seasons and regions with more rainfall: When chlorine-containing fertilizers are applied in rainy seasons or areas with more precipitation, chloride ions can be leached away with water and are not likely to accumulate in the soil, thus avoiding adverse effects on crops. However, in dryland without irrigation conditions, poorly drained saline-alkali land, hot and dry seasons, and areas with water shortages and little rain, it is best not to use chlorine-containing fertilizers or to use them sparingly.

5. Which plants are suitable for chlorine-containing fertilizers?

Various crops differ in their sensitivity to chlorine. Some plants are very sensitive to chloride ions, and when their absorption reaches a certain level, it will noticeably affect yield and quality. These plants are usually called chlorine-avoiding plants.

When chloride ions are abundant, they are not conducive to the conversion of sugar into starch, and the starch content of root and tuber crops will decrease; chloride ions can promote the hydrolysis of carbohydrates, and watermelon, sugar beet, and grapes will have reduced sugar content; when chloride ions are high, they will affect the combustibility of tobacco, and cigarettes tend to go out; when chloride ions are high, they often cause harm to the seedlings of sensitive crops.

Tobacco, potato, sweet potato, sugarcane, watermelon, grapes, citrus, sugar beet, apple, tea, Chinese cabbage, chili pepper, lettuce, and amaranth are all chlorine-avoiding crops. Chlorine has adverse effects on Solanaceae crops. Soybean and green bean have weak chlorine resistance.

For chlorine-sensitive crops such as tobacco, sweet potato, potato, Chinese cabbage, chili pepper, lettuce, amaranth, apple, grapes, tea, and watermelon, when chlorine-containing fertilizers such as ammonium chloride and potassium chloride are applied, the quality of the product is often affected. For example, too much chlorine reduces the combustibility of tobacco and gives it a bad odor; the starch content of tuber crops decreases and their quality becomes poor; the sugar content of fruit is reduced while acidity is higher, making the flavor of the fruit poor, and so on. Therefore, for chlorine-sensitive crops, when choosing fertilizers, try to choose sulfur-containing fertilizers.

On the contrary, for crops that are not sensitive to chlorine, such as rice, sorghum, foxtail millet, cotton, corn, wheat, peanut, soybean, and tomato, applying chlorine-containing fertilizers can not only save on fertilizer purchase costs, but also have even better effects on some crops. For example, for fiber crops such as cotton and hemp, applying potassium chloride helps increase fiber length and toughness; in rice fields, applying chlorine-containing fertilizers often works better than sulfur-containing fertilizers because it can reduce the damage of hydrogen sulfide to rice roots.