Nutrients and their functions in plants

Essential nutrients for plants are divided into three groups as follows:

• Macronutrients or main nutrients: Include plant substances that need large amounts to grow, this group has 3 elements: Protein (N), Phosphorus (P) và Potassium (K).
• Secondary nutrients: Plants need a moderate amount, this group includes: Calcium (Ca), Magnesium (Mg) and Sulfur (S).
• Micronutrients: Includes plant elements that are needed in small amounts, this group includes: Iron (Fe), Copper (Cu), Manganese (Mn), Bor (B), Molybdenum (Mo)…

I – MACRONUTRIENTS:

1. Nitrogen (Protein):

N needs to be supplied in large amounts because N is involved in all plant development processes. N is the main structural component of plant protein, as well as chlorophyll, which has the ability to absorb solar energy to perform photosynthesis, which combines CO₂ from the air with water to create sugars, which are then converted into starch and plant organs. Therefore, when plants lack N, leaves will turn yellow due to lack of chlorophyll, and growth will be stopped. N has a clear effect in activating lush and healthy plant growth. The main N sources are ammonia sulphate, urea, calcium nitrate, calcium ammonium nitrate, sodium nitrate, potassium nitrate, ammonium phosphate.

2. Lan (Phosphorus):

Like Nitrogen, Phosphorus is also involved in plant development, and is a component of the cell nucleus. Phosphorus is necessary in the process of plant root growth and seed germination. The difference between N and P is that P affects plant maturity, fruit formation and ripening, while N strongly affects nutritional organs (including roots, stems, leaves). In fact, adding P can prevent excessive growth in nutritional organs due to excess N. Without P, ​​plants stop growing or grow weakly, but the leaves are still greener than yellow. Roses lacking phosphorus often have dark purple streaks under the leaves, causing the leaves to fall prematurely, then the plant will weaken and stop growing. Cabbage and cauliflower lacking phosphorus often have purple spots on the leaves. It should be noted that this phenomenon may be due to other causes such as the effects of cold weather and is not entirely due to phosphorus deficiency. Symptoms of phosphorus deficiency can be overcome by applying about a handful of superphosphate/m2 of garden area. Superphosphate is the most widely used form of phosphorus. Forms of phosphorus that are completely soluble in water include mono-ammonium phosphate, di-ammonium phosphate, and potassium phosphate. Bone meal provides phosphorus, but it is a slow-dissolving form of phosphorus. Poultry manure contains reasonable amounts of phosphorus.

3. Potassium (Kali):

K is not actually a constituent of plant tissue, but plants need to be provided with large amounts of K for all parts. K affects the control of water in the process of transpiration from plants, K also acts as a catalyst in the process of forming or storing starch, protein… Plants lacking K are often very weak, especially root part. Another symptom of K deficiency is leaf edges becoming brown and shriveled, often referred to as leaf scorch, which then leads to a chain effect where the plant cannot absorb enough water to compensate. transpiration through leaves.

The main commercial source of K is KCl because of its high K content and low price. The main drawback is that in areas with high chlorine content, KCl often leads to chlorine poisoning, this phenomenon is sometimes evident in rose plants and some vegetables when using high amounts of KCl. Using Potassium Sulphate does not lead to this phenomenon. Potassium nitrate is an excellent source of K and has the advantage of providing soluble N at the same time. Natural form of K is found in organic humus, horse, buffalo, sheep manure and especially poultry manure, however these materials should not be left in the rain for too long because K can be easily washed away.

If the soil is highly acidic, K can become insoluble and cannot be absorbed by plants, which can lead to K deficiency. This phenomenon can be overcome by adding lime to increase K levels easily. tan. It should be noted that K is easily soluble and easily washed away during times of heavy rain and flooding, so in tropical areas with high rainfall people often fertilize a lot of K.

4. Calcium:

Calcium makes up the majority of the structure of plant cell walls, similar to the bone structure in animals. Calcium deficiency leads to broken tips or buds. Symptoms of Calcium deficiency are often seen through the crooked shape of the foliage with curled leaf tips and curled leaf edges. Brown spots or dark spots also show symptoms of calcium deficiency. In tomato plants, Ca deficiency symptoms cause the flower stalk or fruit stalk to turn brown and mushy, which will then be attacked by fungi. The cause of this situation may be that water is not provided sufficiently to transport Calcium to all parts, especially the tips and tops of the tree. Calcium deficiency often occurs under very acidic soil conditions, often in areas with excess Mg and Al. All forms of limestone usually contain high amounts of Calcium, Calcium is also present in most types of composted organic humus.

5. Magnesium:

In the composition of chlorophyll there is one Mg atom. If the supply of Mg to the plant is removed or blocked, compounds such as carotenes or xanthophylls are formed and the green parts of the plant will appear orange or yellow instead of green. Plants lacking Mg often have yellow leaves. This phenomenon begins to appear from the main veins of the leaves and gradually spreads. Bright orange streaks appearing on leaves can also be a sign of Mg deficiency symptoms. Leaves affected by Mg deficiency are usually immature leaves. A special case in potato plants is the symptom of Mg deficiency. Mg appears between the leaf veins but the rest of the leaf remains green. Mg is supplied by inorganic chemicals such as magnesium sulphate or dolomite which is a slow acting form of magnesium limestone. Most organic mulches, especially those made from green leaves and green stems, contain significant amounts of magnesium. Mg deficiency often occurs in very acidic soils or where large amounts of K are used, especially potassium sulphate.

6. Sulfur:

Sulfur is a structural component in protein and vegetable oils. Symptoms of sulfur deficiency are similar to those of developed leaves with symptoms of N deficiency. Sulfur deficiency occurs by preventing the growth of leaves or curling leaf edges. However, sulfur deficiency rarely occurs because a large amount of sulfur is found in sulfur salts or sulphates in mixed fertilizers, in organic materials, in the air…

II- CTRACE ELEMENTS:

Although plants need these elements in very small amounts, these elements help plants grow strongly. They are not elements present in the structure of plants, but their activity is like catalysts or oxidants that help plants absorb or use macroelements and secondary elements and then form them. establish different substances in plants.

1. Iron (Fe):

Although iron is not present in chlorophyll, it does support the formation of chlorophyll. Therefore, iron deficiency often leads to yellow leaves, similar to Mg or N deficiency. The main difference is that Mg and N transport are related to each other and respond to growth and development, so Symptoms of Mg and N deficiency appear mainly in mature leaves because Mg and N are withdrawn from these leaves. Meanwhile, iron is an element that does not move in plants, so the yellowing of leaves will first occur in young organs.

Iron is present in most soils but in an insoluble form due to the presence of limestone. Therefore, iron deficiency occurs mainly in plants grown on overly calcareous or overly alkaline soils. The method to overcome iron deficiency is to acidify the soil using sulfur, peat, aluminum sulphate, iron sulphate. In addition, iron tends to turn into insoluble compounds when exposed to other chemicals, so a more effective method is to use chelated iron to apply to the soil or spray through leaves to supply directly to plants. . The chelate form does not combine easily with other substances and has the ability to be transported dynamically in plants.

2. Manganese:

Mn is known as a plant oxidant. Mn deficiency can cause gray or dark yellow spots to appear around the leaf edges. Like Fe, Mn deficiency symptoms often occur on limestone soils because when Mn is applied, Mn becomes insoluble. Performing soil acidification as mentioned in the Fe section will improve this situation significantly, or use manganese sulphate in a soluble form to fertilize the soil. On the contrary, Mn poisoning often occurs in overly acidic soils because Mn becomes soluble quickly, so plants will have excess Mn.

3. Zinc (Zinc):

Zn deficiency symptoms sometimes occur in citrus trees, causing yellow spots to appear on the leaves. Zn deficiency symptoms can be overcome by applying zinc sulphate to the soil.

4. Copper (Copper):

Copper deficiency also easily occurs in citrus trees. Copper deficiency leads to the death of young roots, sometimes burning of leaf edges along with the phenomenon of many but not strong sprouts, and the phenomenon of secretion. sap and sap also occur. Copper deficiency is overcome by applying copper sulphate or spraying copper oxychloride.

5. Boron (Bo):

B is an N-regulatory element in plants. B deficiency causes rotting and hollow cavities on radish plants along with yellow spots on leaves and often causes death of the tips. B deficiency in broccoli causes empty roots and dark brown tumors, after which the plant no longer grows. B deficiency also causes small tumors on the skin of citrus trees, especially lemon trees, which have holes filled with sap in the fruit, sometimes brown spots near the seeds.

B, like K, is easily leached, so soils may experience temporary B deficiency after prolonged periods of rain, especially in areas that become dry. in an unusual way.

Symptoms of B deficiency can be overcome by adding sodium borate or borax but must be used with caution because although borax can be a regulatory factor and aid in N absorption, it can become an herbicide if too large a quantity accumulates.

For medium-sized lemon trees, you should not use more than 1 tablespoon of borax. This amount of borax should be dissolved with water and sprinkled onto the ground in the foliage area. Do this once every 12 months.

6. Molybdenum:

Mo is needed in a very small amount, only a few grams per 1000m2, but lack of Mo causes very serious consequences such as deforming growth in broccoli plants… Lack of Mo leaves curl and stems fall off. During the young plant stage, broccoli and cabbage leaves curl inward with small spots. Shrub-like plants lacking Mo will often have young roots die.

When the soil is too acidic (high acidity), it will prevent plants from absorbing Mo, causing Mo deficiency. Mo deficiency also occurs when fertilizing with high N and P content. Overcome Mo deficiency by spraying sodium molybdate at a dosage of 1 tablespoon dissolved in 4.5 liters of water.

7. Toxicity:

Poisoning phenomenon can occur due to excessive use of trace elements such as Cu, Zn, B, Mn. This phenomenon often occurs in acidic soil because the solubility of the above substances in acidic soil is very large. The manifestation of this symptom is the appearance of small spots on the edge of the leaf, in many cases the entire leaf edge curls like a symptom of K deficiency. In bean plants, yellow color often appears between the leaf veins with brown or dark purple spots. On tomato plants, brown spots appear along the roots, the leaves wilt and the plant often dies. It is necessary to distinguish some pathogenic fungi with similar symptoms as above.

GENERAL DIAGNOSIS:

The above are just a few of the nutritional deficiency symptoms listed. Observing to diagnose nutritional deficiency symptoms is very difficult and complicated because in fact the plant may lack more than one element or It is possible that there is a deficiency of an element and the presence of a toxic element. It is also possible that different elements are present in the soil but cannot be absorbed by the plant because they are insoluble due to the soil being too acidic or too acidic. alkaline or excess of other elements.

However, don’t worry too much about the symptoms of malnutrition. Be aware of the possibility of being a bit heavy-handed in handling alkalinity and acidity, using single fertilizers instead of mixed fertilizers.

Do not use excessive or unnecessary amounts of fertilizer. Sometimes a plant shows signs of not growing just because it is in its resting stage, or because of physical factors such as too much or too little water or soil. There are also times when plants are in danger of root damage due to too much fertilizer in the soil./.