Caution! Do not use chlorine-containing fertilizers carelessly!
1. Rapeseed is a crop that prefers chlorine.
"Chlorine-loving crops" refer to a category of plants that require a large amount of chlorine during their growth and development, or are not sensitive to chloride ions. Applying chlorine-containing fertilizers can significantly increase their yield.
Rapeseed is a typical crop that prefers chlorine. Applying chlorine-based compound fertilizers and other chlorine-containing fertilizers has numerous benefits. Firstly, it boosts yield. Chlorine helps rapeseed grow stronger and produce fuller seeds, directly increasing the yield. Secondly, it enhances disease resistance, especially significantly reducing the occurrence of fungal diseases in rapeseed, which is like providing a "guarantee" for the crops. Thirdly, it is drought-resistant and cold-resistant, enabling rapeseed to better withstand adverse weather conditions. Fourthly, it saves money. For the same effect, chlorine-based fertilizers are much cheaper than sulfur-based ones.
"Chlorine-sensitive crops" do not mean that plants completely lack the chlorine element, but rather that they are extremely sensitive to the concentration of chloride ions (Cl⁻) in the soil. When the concentration of chloride ions reaches a certain level, it will have a negative impact on the crops. Citrus fruits are a typical example of such crops.
The specific hazards of chlorine fertilizer to citrus fruits are:
(1) Seriously affecting fruit quality
Excessive chloride ions will interfere with the metabolism and transportation process of carbohydrates in the fruit trees, resulting in a decrease in the sugar content absorbed by the fruits and an increase in the content of organic acids. As a result, the fruits will not taste sweet, lose their flavor, and have a poorer texture.
(2) The fruit peel becomes thicker and rougher.
Chloride ions can interfere with the normal development of fruit skin cells, potentially causing the skin to thicken and become rough in appearance, thereby affecting the visual quality of the fruit. Studies have shown that chloride stress also reduces the vitamin C content in citrus fruits, leading to a decrease in their nutritional value. Moreover, citrus fruits fertilized with chloride-based fertilizers have poorer storage resistance and are more prone to rotting, which is not conducive to storage and transportation.
(3) Causing "chlorine poisoning" to the root system and leaves
Chloride ions are easily mobile in the soil and are often absorbed in large quantities by the root system. Excessive chloride ions can damage the root tip cells, hindering the normal absorption of water and nutrients such as nitrogen, potassium, and calcium by the root system, resulting in poor root development.
At the same time, excessive chloride ions will be transported to the leaves through transpiration and accumulate at the leaf margins, causing "salt damage". The typical symptoms include the leaf tips and margins of older leaves first showing scorched and yellowing, resembling a burnt appearance. In severe cases, the entire leaf may fall off, significantly weakening the tree's photosynthesis.
III. Special Attention Needed
Different types have different tolerances. Although all citrus fruits are intolerant to chlorine, the tolerance levels vary among different types. Generally speaking, the citrus fruits with the tangerine rootstock (which account for most of the production areas in China) are the most sensitive to chlorine; while the citrus fruits with the orange rootstock are slightly better, but it is still not recommended to use them.
Young plants are more sensitive than mature trees. The root system of young trees is not yet fully developed, and they have a weaker resistance to chloride ions. Once damaged, it is difficult for them to recover, which will seriously affect their growth in the later stage.
(1) How to Select the Optimal Fertilizer for Citrus Trees
To ensure high yield, high quality and high efficiency of citrus fruits, the preferred choice is the sulfur-based compound fertilizer specially designed for economic crops such as citrus. When purchasing, make sure to recognize the labels indicating "sulfate of potassium type" or "S base".
According to national standards, the packaging of chlorine-containing compound fertilizers must clearly indicate "Chlorine-containing (low chlorine)", "Chlorine-containing (medium chlorine)" or "Chlorine-containing (high chlorine)". Citrus, tea, tobacco, potatoes and other crops that are sensitive to chlorine should completely avoid all fertilizers with the "chlorine" label.
(2) How to handle mistakes made
If a small amount of chlorine-based fertilizer is applied and detected in time, immediately flood the soil with water to wash away the surface chlorine ions and dilute the concentration. At the same time, enhance drainage to prevent waterlogging from causing secondary damage. For subsequent fertilization, switch to sulfur-based fertilizer or pure potassium sulfate, and add organic fertilizer to improve soil structure.
