At present, most of the compound (mixed) fertilizers and special fertilizers sold on the market contain chlorine. Since chlorine is a trace element, excessive application will cause chlorine poisoning in crops. In order to prevent chlorine poisoning of crops and fruit trees, the following five aspects should be considered when applying chlorine-containing fertilizers:
First, considering the characteristics of crops, the crops are divided into three types in theory and practice according to the tolerability of chlorine ions:
(1) Strong chlorine-tolerant crops mainly refer to rice, sorghum, and millet in cereal crops, as well as cotton, hemp, and spinach. Such crops can be in conditions where soil chlorine is not high (
(2) Chlorine-resistant medium crops, mainly barley, wheat, corn, soybeans, peas, broad beans, oil radish, peanuts, radish, tomatoes, cucumbers, etc. Such crops can be applied to chlorine-containing fertilizers in a constant amount under conditions of low soil chlorine content.
(3) Crops with weak chlorine resistance include mainly sweet potatoes, flue-cured tobacco, lettuce, cabbage, raspberry, and apples. It is not appropriate to apply ammonium chloride (NH4Cl), potassium chloride (KCI), and various compound fertilizers and special fertilizers based on these two fertilizers. However, potassium chloride (KCl) may be applied in an appropriate amount when the soil contains less than 50 mg/kg of chlorine.
Second, from the consideration of fertilizer characteristics, most of the compound fertilizers and special fertilizers contain chlorine (C1) because such fertilizers are made of ammonium chloride (NH4CI) and potassium chloride (KC1) as the basic raw materials. Chlorine content is generally not less than 15%; the other part of organic-inorganic multicomponent fertilizer has chlorine content of not less than 4.5%, but due to the presence of organic substances, the toxicity of chloride ions is reduced through biological, chemical and physical effects. Therefore, the dosage can be increased as appropriate. Chlorine-containing fertilizers are generally acidic fertilizers, and should not be mixed with alkaline fertilizers, otherwise it will cause a decrease in fertilizer efficiency. If 100 kg of fertilizer containing 15% Mushi Chloride is used, the average content of chlorine in the soil (20cm) will increase by 50.8mg/kg. This shows that due to the application of chlorine-containing fertilizer, a large amount of chlorine will be brought into the soil. It may cause the accumulation of local chlorine in the soil and eventually cause chlorine poisoning in the crop.
Third, from the soil characteristics, in general, when the chlorine content of the soil is lower than the critical chlorine-resistant value of 100-300mg/kg, the chlorine-containing fertilizer can be applied. When the soil chlorine content is less than 50mg/kg, all crops can be applied with chlorinated fertilizer; when the soil contains 50-100mg/kg chlorine, except for weak chlorine-resistant crops such as lettuce, most crops can be applied ammonia chloride, chlorine Potassium; in the soil with high chlorine content, ie, 100-200mg/kg, most crops can be applied potassium chloride, generally not suitable for the application of ammonium chloride; when the soil chlorine is greater than 200mg/kg, generally not suitable for chlorine fertilizer. Specific use is as follows
1. Paddy field: Paddy rice is a strong chlorine-tolerant crop. Ammonium chloride and potassium chloride are inexpensive and are ideal for rice and potash fertilizers in rice fields. Paddy soil has sufficient water, which can dilute the chlorinated fertilizer with strong salinity. Chlorine is the most easily moved element. Chlorine is most likely to be lost or leaked in water without causing salt and chlorine damage. Therefore, chlorinated fertilizers should be used first in paddy fields. Generally, 40-50 kg of ammonium chloride and 5 to 10 kg of potassium chloride are applied per acre of paddy fields. Spread the base fertilizer first, then plow, then flatten, then transplant.
2, irrigated land: irrigated on the ground although the cultivation of dry field crops, but irrigation water guarantee can be combined with fertilizer, application of chlorinated fertilizer combined with irrigation, can reduce the high concentration of local fertilizer on the crop damage. Base fertilizer can be used as seed fertilizer, and the spacing between fertilizer and seeds is 8 cm. The top dressing is 8 to 10 cm away from the root and is deeply applied to the soil. The application of irrigated land is better than that of dry land. Peanuts are crops with low to moderate chlorine tolerance, and it is not appropriate to use ammonium chloride. The use of potassium chloride and chlorine-containing compound fertilizers requires careful and controlled use.
3, dry fields: the dry land without irrigation conditions with chlorinated fertilizer must pay attention to the amount and location of fertilizer application, to prevent burning roots, burning seedlings. Base fertilizer can be done, top dressing, can not do fertilizer. The corn, wheat seeds and fertilizer interval soil need 8 cm. Soybeans and cotton need 10 to 11 centimeters. As long as the dosage is appropriate and the usage is appropriate, the increase rate of ammonium chloride and urea in the case of equal amount of nitrogen is almost equal; under the condition of equal potassium, the increase yield of potassium chloride and potassium sulfate is basically the same. Generally, 5 to 10 kg of potassium chloride is applied per acre, and 15 to 25 kg of chlorine-containing compound fertilizer each containing 15% of nitrogen, phosphorus and potassium are used. Ammonium chloride is best used in rice fields and irrigated fields.
Fourth, from the fertilization method to consider, the application of chlorine-containing fertilizers, in principle, should be deep-buried, concentrated application. However, in practice, it can be uniformly removed before soil preparation, deep into the soil, in order to avoid excessive concentration of chloride ions on the roots of the crop caused by poisoning; at the same time pay attention to the chlorine-containing fertilizer can not be seed dressing, not to do seed fertilizer directly applied to the same position in the seed, and Should be applied to the lower side of the seed or both sides l0cm, so as not to burn the seeds, affecting the crop emergence and growth. A better method of application is to mix with ring fertilizer (acid) or organic fertilizer (acid). For example, in the application of chlorinated fertilizers, combined with the application of decomposed organic fertilizers, the fertilizer efficiency of chlorinated fertilizers can be increased, and the adverse effects of chloride ions can be reduced. In soils with low effective phosphorus content, chloride ions have an inhibitory effect on phosphorus uptake by crops, often resulting in lack of phosphorus for crop growth. Therefore, when applying chlorinated fertilizers, it is necessary to pay attention to appropriate amounts of phosphate fertilizers; with chlorinated fertilizers and urea, Complex (mixed) Hefei and formula fertilizers such as ammonium phosphate, superphosphate, calcium magnesium phosphate, etc. can not only reduce the harm of chloride ions, but also have the effect of balanced fertilization due to the combined use of nitrogen, phosphorus and potassium. .
5. From the perspective of climate and field management, if it is a humid and rainy climate, chlorine-containing fertilizers can be applied according to the constant amount; for certain chlorine-resistant crops that require large amounts of water and are often irrigated, chlorinated fertilizers can also be applied according to constant amounts.
In recent years, there has been a lot of fertilizer damage caused by the excessive chloride ion content in fertilizers, making farmers' friends have a resistance against chlorine ions. In fact, most of the chemical fertilizers have acceptable levels of chloride ions. However, due to farmers’ long-term excessive use of chemical fertilizers and pesticides, the accumulation of chloride ions increases, together with the serious destruction of the soil pellet structure and the reduction of soil buffering capacity, it has caused damage. The constant increase.