Chemical fertilizers are mineral substances that have one or more elements needed to feed plants. These fertilizers increase plant growth and are produced through chemical processes. In addition, chemical fertilizers increase the effectiveness of soil by improving its climate maintenance.
Today, chemical fertilizers play a role in providing about 40 to 60% of the world’s food resources. Chemical fertilizer can be added to the soil, sprayed directly on the leaves of plants, or dissolved in water and added to the soil of plants. Chemical fertilizers are used in order to increase the quality of the soil, increase the amount of the product or improve the quality of the produced product. Due to their mineral nature, these fertilizers are immediately decomposed and provided to the plant, thus increasing the growth rate and qualitative and quantitative performance of the plant in less time.
The methods of using different fertilizers are different according to their absorption and stability. The required elements are divided into two categories: high consumption (macro) and low consumption (micro). High consumption elements such as nitrogen (nitrogen), phosphorus, potassium, sulfur, calcium and magnesium and low consumption elements include: iron, copper, boron, zinc, chlorine and molybdenum. There are many types of chemical fertilizers that are produced in powder, granule, liquid and gas forms and are used by farmers.
Reasons for use and effects of lack of some main elements in plant growth
Chemical fertilizers mostly include combinations of nitrogen, phosphorus and potassium, which are added to the soil to increase crop production.
Generally, a plant that is deficient in nitrogen is small and grows slowly; Because these plants do not have enough nitrogen needed to make basic and genetic materials. These plants are often pale green or yellowish due to not having enough chlorophyll. Older leaves become dead tissue and die. There are 3 forms of nitrogen (nitrogen) in this fertilizer: urea (10%), nitrate (6%) and ammonium (4%). For this reason, at appropriate times after fertilization, this element is absorbed by the plant and absorption efficiency increases.
If the plant is deficient in phosphorus, symptoms will definitely appear in the plant. For example, the growth of the plant is very slow or stops. These plants often suffer from leaf fall or flower fall, and their leaves change color and usually the edges of the leaves turn purple or red.
Sometimes the symptoms of phosphorus deficiency are similar to nitrogen deficiency in plants. In phosphorus deficiency, the growth of the aerial part and the root slows down or stops. The leaves of the plants are short, narrow and thin, and in this case the petioles form a small angle with the branch. The longitudinal growth of the plant becomes vertical and the lateral branches grow less. The leaves turn dark green, bluish or purple, and sometimes spots or stripes of the same color appear on the leaves. The number of leaves is reduced, the buds die and the number of flowers also decreases. Therefore, the fruit yield is also reduced. When there is a lack of phosphorus in some fruits, the flesh of the fruit is soft and the fruit juice is very sour and its storage properties are reduced.
If the plants are suffering from potassium deficiency, the tips and margins of their leaves, especially in the lower leaves, are burnt, which is called tip burn or lip burn. Also, when there is a lack of potassium in a plant, the thirst of the plant shows itself faster and the plant quickly withers and loses its freshness. If plants suffer from potassium deficiency, they often show the following symptoms. Stopping growth in general, shortening between the nodes and keeping the leaves short, fruits with elongated tips and lack of development in the tail part of the fruit.
Application and uses of the main elements
Helping photosynthesis and improving product quality, increasing seed and fruit, faster growth of plant foliage are among the benefits of using nitrogen fertilizers. Also, nitrogen is one of the important nutritional elements in increasing yield and helps the optimal growth of plants.
Phosphorus helps to create a strong and healthy rooting system in plants. A high percentage of phosphorus stimulates rooting, increases flowering and increases fruit formation. Phosphorus is the most important factor in the correct process of photosynthesis for the plant. Phosphorus also helps in more root formation and the increase of flowers.
The potassium in the fertilizer helps to improve fruiting or seed filling and has a significant effect on the coloring of agricultural, garden and greenhouse crops and ultimately increases the quantity and quality of the product. Potash significantly contributes to the flowering of ornamental plants and the growth of fruit in fruit trees. Fertilizers containing high amounts of potassium cause the fruit to ripen and increase the quality of the product. Generally, potassium-containing fertilizers are effective in strong stem growth, water movement in plants, flowering progress and plant fertility.
Technical description
Although nitrogen makes up most of the atmosphere, it is in a form that is not available to plants. Nitrogen is the most important fertilizer, because this element is present in DNA, protein and other plant components (such as chlorophyll) and is very effective in the growth of leaves. Only some bacteria and their host plants (especially legumes) can stabilize the nitrogen in the atmosphere (N2) by converting it into ammonia. Phosphate is required for the production of ATP and DNA, the main energy carrier in cells, as well as some lipids.
Nitrogen can be absorbed by plants in the form of nitrate, ammonium ion and urea. Ammonium nitrate has 33% nitrogen and both forms of nitrogen can be absorbed by plants. This fertilizer is more stable than urea fertilizer (the most common agricultural fertilizer in Iran). Urea is an organic compound and can be absorbed by plants in this form d. Urea is also used in leaf spraying of plants. Urea and ammonium nitrate can be added to the soil before planting the crop and after the plant has grown a little.
In general, the percentage of phosphorus in chemical fertilizers is stated as the percentage of phosphorus oxide. Phosphoric acid, which is obtained from the decomposition of soil organic matter, can be absorbed by plants, but it is not used as a chemical fertilizer. Most of the phosphorus fertilizers applied to the soil are stabilized by calcium in alkaline soils and by iron and aluminum in acidic soils. Usually, phosphorus fertilizers that are given to the soil remain absorbable by the plant in the first year, and a small part becomes absorbable by the plant in the following years. This element generally causes the development of roots, flowers, seeds, and fruits.
The solubility and movement of phosphorus fertilizer in the soil is very limited. Phosphorous fertilizers should be applied to the soil before planting and placed directly in the root development zone. The maximum amount of phosphorus solution is observed at pH 6 to 6.5. Therefore, bringing the pH of the soil to these limits can be effective in increasing the solubility and absorption of phosphorus. Changing soil pH can be done in acidic soils by adding lime and in alkaline soils by adding acidic or sulfur fertilizers.
Most of the potassium fertilizers are soluble in water and the method of adding them to the soil does not play a big role in the effectiveness of the fertilizer. Potassium chloride is the most abundant potassium compound in nature. Potassium deficiency is mostly seen in acidic soils and sandy soils, but its deficiency is also observed in other soils under irrigation conditions and harvesting a large amount of crops (especially alfalfa). Potassium sulfate is the most common potassium fertilizer used in agriculture. Potassium is also added to the soil from the primary decomposition of plant residues, but soil humus is not considered as a significant source of potassium, because potassium is not stabilized by organic matter.
Potassium nitrate contains 44% potassium oxide, but it is an expensive fertilizer. Soils with a large amount of vermiculite and illite clay stabilize potassium. Potassium chloride has a large amount of potassium (60 to 62%). However, indiscriminate consumption of potassium chloride is not very desirable in cases where a large amount of potassium is needed; Because there is a possibility of poisoning due to the abundance of chlorine. Although some chlorine is necessary for products such as tobacco and cotton, too much chlorine in the soil causes the quality of tobacco to decrease and the potato tuber to become watery.
No Comments