Phosphate fertilizer for growth and lush flowering. The effect of phosphorus on plant life

Phosphorus in plants

Phosphorus plays exclusively important role in plant life. Most metabolic processes are carried out only with his participation. It is almost always in the second minimum (after nitrogen).

The physiological role of phosphorus (C 3). It is part of the most important organic compounds actively involved in plant metabolism: nucleic acids (DNA and RNA), nucleoproteins, phosphoproteins, phosphatides (phospholipids), macroergic compounds (ATP, etc.), sugar phosphates, phytin, vitamins, etc. Phosphorus content (Р2О5) in plants and removal by agricultural crops The average content is 0.5% of dry matter, varying from 0.1 to 1.5%, and depends on the biological characteristics of crops, the age of plants and their organs, the conditions of phosphorus nutrition, etc. .d. So, the grain of leguminous crops contains 1-1.5% P2O5, cereals - 0.8-1%. The straw of those and other crops contains less phosphorus compared to seeds - 0.2-0.4%.

Phosphorus in plants is distributed similarly to nitrogen, is its companion. On average, the content of phosphorus in plant organs is 30% of the amount of nitrogen (C 17). More phosphorus is found in young and vital organs, leaves contain more phosphorus than stems.

The removal of phosphorus by crops averages 15-50 kg/ha, varying depending on the biological characteristics of crops and the level of productivity.

Sources of phosphorus for plants. The main sources are salts of orthophosphoric acid (C 19), which, being tribasic, is capable of forming three types of anions - H2PO4–, HPO42–, PO43– (C 20) and, therefore, three types of salts - one-, two- and three-substituted phosphates , whose solubility and availability for plants varies depending on the cations.

Salts of metaphosphoric and polyphosphoric (pyro-, tripolyphosphoric, etc.) acids, which are not directly absorbed by plants, but are hydrolyzed in the soil to orthophosphates (C 21-24), can also be sources of phosphorus.

In addition, the roots of some plants (peas, beans, corn, etc.) secrete the enzyme phosphatase, which splits off the phosphoric acid anion from simple organic compounds. As a result, the organic compounds of phosphorus can serve as a source of phosphorus for these plants.

Phosphorus transformations in plants. The phosphorus that enters the plants very quickly passes into the composition of organic compounds. However, phosphorus is in them directly in the form of a residue of phosphoric acid. Thus, 85-95% of phosphorus is in organic form (C 26). Mineral phosphates - calcium, potassium, magnesium and ammonium phosphates - are much less (5-15%), but they have great importance, being a reserve and transport form of phosphorus. For example, phosphorus in the organic compounds of the roots can move to the aerial part only after transformation into mineral phosphates.

Dynamics of phosphorus consumption during the growing season. The critical period in relation to phosphorus in all cultures is noted in the phase of seedlings. The lack of phosphorus during this period sharply reduces the yield, regardless of the further supply of plants. At the same time, the root system in the initial phases of growth is poorly developed and often cannot absorb soil phosphorus and fertilizers applied before sowing in sufficient quantities. Therefore, pre-sowing application of phosphorus is widely recommended.

The periods of maximum consumption of phosphorus by different cultures do not coincide. For example, spring wheat consumes all the phosphorus it needs by the end of the earing phase, while flax absorbs only 58% even by the full flowering period, and cotton absorbs only 10% of the maximum phosphorus content in plants in the full flowering phase. The absorption of phosphorus in wheat is observed in the phases of emergence into the tube and earing, in flax - in the phases of flowering and ripening, in cotton - during the period of fiber formation.

Signs of a lack of phosphorus for plants. The growth and development of plants slows down, the size of the leaves decreases, flowering and ripening of the crop are delayed (C 31-33). Phosphorus is recycled, so its deficiency first appears on the lower leaves, which turn dark green, dirty green, and then red-violet, purple or purple

Phosphorus in soils.Content and reserves of phosphorus in soils. The total content varies from 0.01 to 0.3% and depends primarily on the mineralogical composition of the parent rocks. In addition, soils rich in humus contain more phosphorus (humus contains 1-2% P2O5). Thus, the minimum content of phosphorus in soddy-podzolic sandy soils, the maximum - in chernozem soils. The vital activity of plants causes the biological accumulation of phosphorus in the upper soil horizons

The total reserve of phosphorus in the arable layer per 1 ha varies from 0.3 tons in light soddy-podzolic soils to 9 tons in chernozems

Forms of phosphorus in soils and its transformation Phosphorus in soils is in organic and mineral forms Organic phosphorus is less, it is part of the nonspecific part of humus, as well as undecomposed remains of plants and microorganisms.

Mineral phosphorus predominates, which in soddy-podzolic, chestnut soils and gray soils is 70-90% of the total content, and in soils with a high content of humus (hence, organic phosphorus) - gray forest soils and chernozems - 55-65% (C 44). Mineral phosphorus is mainly found in the form of primary minerals and, above all, fluorapatite [Ca3(PO4)2]3·CaF2 and hydroxyapatite [Ca3(PO4)2]3·Ca(OH)2.

Phosphorus of organic compounds and primary minerals is not directly absorbed by plants. As a result of weathering of primary minerals, secondary minerals are formed, which are various salts of orthophosphoric acid. Phosphates are also formed during the mineralization of organic phosphorus under the influence of phosphorobacteria.

Salts of phosphoric acid are characterized by different solubility and, consequently, availability to plants.

Phosphates of monovalent cations [KH2PO4, (NH4)2HPO4, Na3PO4], as well as monosubstituted salts of divalent cations [Ca(H2PO4)2, Mg(H2PO4)2] are water-soluble. They are well available to plants.

Disubstituted calcium and magnesium phosphates (CaHPO4, MgHPO4) and freshly precipitated, amorphous three-substituted phosphates [Ca3(PO4)2, Mg3(PO4)2], which are insoluble in water, but dissolve in weak acids (organic, carbonic) are called acid-soluble. . These compounds, under the action of acidic root secretions, as well as organic and mineral acids produced by microbes, gradually dissolve and become available to plants.

They do not dissolve in water and weak acids, as a result, crystalline forms of three-substituted calcium and magnesium phosphates are practically inaccessible to plants. But some plants - lupins, buckwheat, mustard, to a lesser extent peas, sweet clover, sainfoin and hemp - have the ability to absorb phosphorus from trisubstituted phosphates. Iron and aluminum phosphates (AlPO4, FePO4) are the least available to plants. An important role in the formation of phosphorus nutrition conditions is played by the chemical absorption of water-soluble phosphates (phosphorus retrogradation), which occurs in soils with any reaction of the environment.

In neutral soils saturated with bases (chernozems, chestnut soils), two- and three-substituted calcium and magnesium phosphates are formed:

Ca(H2PO4)2 + Ca(HCO3)2 → 2CaHPO4↓ + 2H2CO3;

PPK)Ca2+ + Ca(H2PO4)2 → PPK)2H+ + Ca3(PO4)2↓.

AT acidic soils, characterized by a high content of aluminum and iron (soddy-podzolic, red soils), phosphates of these elements precipitate:

Ca(H2PO4)2 + 2Fe3+ → 2FePO4↓ + Ca2+ + 4H+;

PPK)Al3+ + K3PO4 → PPK)3K+ + AlPO4↓.

As a result of retrogradation, water-soluble phosphates are found in soils in insignificant amounts (as a rule, no more than 1 mg/kg of soil).

Anions of phosphoric acid in the soil can be exchange absorbed, fixing on the surface of positively charged colloidal particles of aluminum and iron hydroxides. To a greater extent, the exchange absorption of phosphates is expressed in the acid reaction of the medium. The process of exchange absorption is reversible, that is, phosphate ions are capable of being displaced from the FPC into the solution by other anions. As a result, the exchange-absorbed anions of phosphoric acid are readily available to plants.

Soluble salts of phosphorus are consumed not only by plants, but also by microorganisms, turning into organic phosphorus-containing compounds. After the death of microbes, the main amount of biologically absorbed phosphorus again becomes available to plants, with the exception of a small part that has passed into the composition of humus.

For soddy-podzolic and gray forest soils, the Kirsanov method is standardized: the extract is 0.2 N. HCl, water-soluble and acid-soluble salts of phosphoric acid pass into the solution.

In non-carbonate chernozems, the content of mobile phosphorus is determined according to Chirikov: the soil is cultivated with 0.5 n. CH3COOH.

On carbonate soils, acids are not used, since weakly acidic extracts are spent on the decomposition of carbonates, while more concentrated ones can dissolve phosphates that are inaccessible to plants. Therefore, the content of mobile phosphorus in carbonate chernozems is determined according to Machigin using 1% (NH4)2CO3, which has an alkaline reaction.

Absolute results obtained by any method are not informative, since the constant impact of plant roots on the soil during the growing season is far from equivalent to the dissolving power of any reagent. For example, when the solution interacts with the soil, an equilibrium is established, and in the presence of plants that consume phosphorus, its concentration in the liquid phase of the soil constantly decreases, stimulating the transition of new amounts of phosphates into the solution.

However, comparing crop yields in field experiments conducted on soils with different contents of mobile phosphorus, one can conclude how well a particular soil is provided with phosphorus, and express the resulting pattern in the form of a grouping that has practical significance.

Phosphorus balance in soils

Incoming articles:

1) mineral and organic fertilizers- main;

2) plant seeds - 2-3 kg/ha year.

Expenditure items:

1) removal of agricultural crops - the main one;

2) losses as a result of water erosion - 5-10 kg/ha·year;

3) leaching into groundwater - observed only on light and peaty soils, where it can reach 3-5 kg/ha·year.

An analysis of income items shows the absence of any significant sources of compensation for phosphorus losses from the soil, except for fertilizers. Mineral fertilizers play an exceptional role in ensuring a deficit-free balance of phosphorus, because much less phosphorus returns to the soil as part of organic fertilizers than is alienated by crops.

The role of elements in plant life -

Nitrogen

Nitrogen is one of the main elements needed by plants. It is part of all proteins (its content ranges from 15 to 19%), nucleic acids, amino acids, chlorophyll, enzymes, many vitamins, lipoids and other organic compounds formed in plants. The total nitrogen content in the plant is 0.2 - 5% or more of the mass of air - dry matter.

In the free state, nitrogen is an inert gas, which contains 75.5% of its mass in the atmosphere. However, in its elemental form, nitrogen cannot be assimilated by plants, with the exception of legumes, which use nitrogen compounds produced by nodule bacteria developing on their roots, which are able to assimilate atmospheric nitrogen and convert it into available nitrogen. higher plants form.

Nitrogen is absorbed by plants only after it is combined with other chemical elements in the form of ammonium and nitrates - the most available forms of nitrogen in the soil. Ammonium, being a reduced form of nitrogen, is easily used in the synthesis of amino acids and proteins when absorbed by plants. The synthesis of amino acids and proteins from reduced forms of nitrogen occurs faster and with less energy than synthesis from nitrates, for the reduction of which to ammonia the plant needs additional energy. However, the nitrate form of nitrogen is safer for plants than ammonia, since high concentrations of ammonia in plant tissues cause their poisoning and death.

Ammonia accumulates in the plant when there is a lack of carbohydrates, which are necessary for the synthesis of amino acids and proteins. Carbohydrate deficiency in plants is usually observed in initial period vegetation, when the assimilation surface of the leaves has not yet developed enough to satisfy the need of plants for carbohydrates. Therefore, ammonia nitrogen can be toxic to crops whose seeds are poor in carbohydrates (sugar beet, etc.). With the development of the assimilation surface and the synthesis of carbohydrates, the efficiency of ammonia nutrition increases, and plants absorb ammonia better than nitrates. During the initial period of growth, these crops must be provided with nitrogen in the nitrate form, while crops such as potatoes, whose tubers are rich in carbohydrates, can use nitrogen in the ammonia form.

With a lack of nitrogen, plant growth slows down, the intensity of tillering of cereals and the flowering of fruit and berry crops, the growing season is shortened, the protein content is reduced and the yield is reduced.

Phosphorus

Phosphorus is involved in metabolism, cell division, reproduction, transmission of hereditary properties and in other the most complex processes occurring in the plant. It is part of complex proteins (nucleoproteins), nucleic acids, phosphatides, enzymes, vitamins, phytin and other biologically active substances. A significant amount of phosphorus is found in plants in mineral and organic forms. The mineral compounds of phosphorus are in the form of phosphoric acid, which is used by the plant primarily in the processes of carbohydrate conversion. These processes affect the accumulation of sugar in sugar beet, starch in potato tubers, etc.

The role of phosphorus, which is part of organic compounds, is especially great. A significant part of it is presented in the form of phytin - a typical reserve form of organic phosphorus. Most of this element is found in the reproductive organs and young tissues of plants, where intensive synthesis processes take place. Experiments with labeled (radioactive) phosphorus showed that there is several times more of it at the growth points of a plant than in the leaves.

Phosphorus can move from old plant organs to young ones. Phosphorus is especially necessary for young plants, as it promotes the development of the root system, increases the intensity of tillering of grain crops. It has been established that by increasing the content of soluble carbohydrates in the cell sap, phosphorus enhances the winter hardiness of winter crops.

Like nitrogen, phosphorus is one of the important elements plant nutrition. At the very beginning of growth, the plant experiences an increased need for phosphorus, which is covered by the reserves of this element in the seeds. On soils poor in fertility, young plants, after the consumption of phosphorus from seeds, show signs of phosphorus starvation. Therefore, on soils containing a small amount of mobile phosphorus, it is recommended to carry out row-by-row application of granulated superphosphate simultaneously with sowing.

Phosphorus, unlike nitrogen, accelerates the development of crops, stimulates the processes of fertilization, the formation and ripening of fruits.

The main source of phosphorus for plants are salts of orthophosphoric acid, usually called phosphoric. Plant roots absorb phosphorus in the form of anions of this acid. The most accessible for plants are water-soluble monosubstituted salts of orthophosphoric acid: Ca (H 2 PO 4) 2 - H 2 O, KH 2 PO 4 NH 4 H 2 PO 4 NaH 2 PO 4, Mg (H 2 PO 4) 2.

Potassium

Potassium is not part of the organic compounds of plants. However, he plays the most important physiological role in the carbohydrate and protein metabolism of plants, activates the use of nitrogen in the ammonia form, affects the physical state of cell colloids, increases the water-retaining capacity of protoplasm, the resistance of plants to wilting and premature dehydration, and thereby increases the resistance of plants to short-term droughts.

With a lack of potassium (despite a sufficient amount of carbohydrates and nitrogen), the movement of carbohydrates is suppressed in plants, the intensity of photosynthesis, nitrate reduction and protein synthesis decreases.

Potassium affects the formation of cell membranes, increases the strength of cereal stems and their resistance to lodging.

The quality of the crop significantly depends on potassium. Its deficiency leads to the frailty of seeds, a decrease in their germination and vitality; plants are easily attacked by fungi and bacterial diseases. Potassium improves shape and taste qualities potatoes, increases the sugar content in sugar beets, affects not only the color and aroma of strawberries, apples, peaches, grapes, but also the juiciness of oranges, improves the quality of grain, tobacco leaf, vegetable crops, cotton fiber, flax, hemp. Nai large quantity Potassium is required by plants during their intensive growth.

Increased demand for potassium nutrition is observed in root crops, vegetable crops, sunflower, buckwheat, and tobacco.

Potassium in the plant is located mainly in the cell sap in the form of cations bound by organic acids, and is easily washed out of plant residues. It is characterized by repeated use (recycling). It easily moves from the old tissues of the plant, where it has already been used, to the young ones.

The lack of potassium, as well as its excess, adversely affects the quantity of the crop and its quality.

Magnesium

Magnesium is part of chlorophyll and is directly involved in photosynthesis. Chlorophyll contains about 10% of the total amount of magnesium in the green parts of plants. Magnesium is also associated with the formation of leaf pigments such as xanthophyll and carotene. Magnesium is also part of the reserve substance phytin contained in the seeds of plants and pectin substances. About 70 - 75% of magnesium in plants is in mineral form, mainly in the form of ions.

Magnesium ions are adsorptively bound to cell colloids and, along with other cations, maintain ionic equilibrium in plasma; like potassium ions, they help to thicken the plasma, reduce its swelling, and also participate as catalysts in a number of biochemical reactions occurring in the plant. Magnesium activates the activity of many enzymes involved in the formation and conversion of carbohydrates, proteins, organic acids, fats; affects the movement and transformation of phosphorus compounds, fruit formation and seed quality; accelerates the ripening of seeds of grain crops; improves the quality of the crop, the content of fat and carbohydrates in plants, the frost resistance of citrus fruits, fruit and winter crops.

The highest magnesium content in vegetative organs plants observed during the flowering period. After flowering, the amount of chlorophyll in the plant decreases sharply, and magnesium flows from the leaves and stems to the seeds, where phytin and magnesium phosphate are formed. Therefore, magnesium, like potassium, can move in the plant from one organ to another.

At high yields crops consume magnesium up to 80 kg per 1 ha. The largest number it is absorbed by potatoes, fodder and sugar beets, tobacco, and legumes.

The most important form for plant nutrition is exchangeable magnesium, which, depending on the type of soil, makes up 5-10% of the total content of this element in the soil.

Calcium

Calcium is involved in the carbohydrate and protein metabolism of plants, the formation and growth of chloroplasts. Like magnesium and other cations, calcium maintains a certain physiological balance of ions in the cell, neutralizes organic acids, and affects the viscosity and permeability of protoplasm. Calcium is necessary for the normal nutrition of plants with ammonia nitrogen; it makes it difficult to restore nitrates to ammonia in plants. The construction of normal cell membranes depends to a greater extent on calcium.

Unlike nitrogen, phosphorus and potassium, which are usually found in young tissues, calcium is contained in significant quantities in old tissues; while it is more in the leaves and stems than in the seeds. So, in pea seeds, calcium is 0.9% of air - dry matter, and in straw - 1.82%

Perennial leguminous grasses consume the largest amount of calcium - about 120 kg of CaO per 1 ha.

The lack of calcium in field conditions observed on very acidic, especially sandy, soils and solonetz soils, where the entry of calcium into plants is inhibited by hydrogen ions on acidic soils and sodium ions on solonetz soils.

Sulfur

Sulfur is part of the amino acids cystine and methionine, as well as glutathione, a substance found in all plant cells and playing a certain role in metabolism and in redox processes, as it is a carrier of hydrogen. Sulfur is an indispensable component of some oils (mustard, garlic) and vitamins (thiamine, biotin), it affects the formation of chlorophyll, promotes enhanced development of plant roots and nodule bacteria, assimilating atmospheric nitrogen and living in symbiosis with legumes. Part of the sulfur is found in plants in an inorganic oxidized form.

On average, plants contain about 0.2 - 0.4% sulfur from dry matter, or about 10% in ash. Most of all, sulfur is absorbed by crops from the cruciferous family (cabbage, mustard, etc.). Agricultural crops consume the following amount of sulfur (kgha): cereals and potatoes - 10 - 15, sugar beet and legumes - 20 - 30, cabbage - 40 - 70.

Sulfur starvation is most often observed on sandy loamy and sandy soils of the non-chernozem zone poor in organic matter.

Iron

Iron is consumed by plants in much smaller quantities (1 - 10 kg per 1 ha) than other macronutrients. It is part of the enzymes involved in the creation of chlorophyll, although this element is not included in it. Iron is involved in the redox processes occurring in plants, as it is able to move from an oxidized form to a ferrous one and vice versa. In addition, the process of plant respiration is impossible without iron, since it is integral part respiratory enzymes.

Iron deficiency leads to the breakdown of growth substances (auxins) synthesized by plants. Leaves become light yellow. Iron cannot, like potassium and magnesium, move from old tissues to young ones (i.e., be reused by the plant).

Iron starvation is most often manifested on carbonate and heavily limed soils. Particularly sensitive to iron deficiency fruit crops and grapes. With prolonged iron starvation, their apical shoots die off.

Bor

Boron is found in plants in negligible amounts: 1 mg per 1 kg of dry matter. Various plants consume from 20 to 270 g of boron per 1 ha. The lowest content of boron is observed in cereal crops. Despite this, boron has big influence on the synthesis of carbohydrates, their transformation and movement in plants, the formation of reproductive organs, fertilization, root growth, redox processes, protein and nucleic metabolism, on the synthesis and movement of growth stimulants. The presence of boron is also associated with the activity of enzymes, osmotic processes and hydration of plasma colloids, drought and salt resistance of plants, the content of vitamins in plants - ascorbic acid, thiamine, riboflavin. The uptake of boron by plants increases the uptake of other nutrients. This element is not able to move from old plant tissues to young ones.

With a lack of boron, plant growth slows down, growth points of shoots and roots die off, buds do not open, flowers fall off, cells in young tissues disintegrate, cracks appear, plant organs turn black and acquire an irregular shape.

Boron deficiency is most often manifested on soils with a neutral and alkaline reaction, as well as on calcareous soils, since calcium interferes with the flow of boron into the plant.

Molybdenum

Molybdenum is absorbed by plants in smaller quantities than other trace elements. For 1 kg of dry matter of plants there are 0.1 - 1.3 mg of molybdenum. The largest amount of this element is found in the seeds of legumes - up to 18 mg per 1 kg of dry matter. From 1 hectare plants endure with a yield of 12 - 25 g of molybdenum.

In plants, molybdenum is part of the enzymes involved in the reduction of nitrates to ammonia. With a lack of molybdenum, nitrates accumulate in plants and nitrogen metabolism is disturbed. Molybdenum improves the calcium nutrition of plants. Due to the ability to change valency (donating an electron, it becomes hexavalent, and attaching it becomes pentavalent), molybdenum is involved in the redox processes occurring in the plant, as well as in the formation of chlorophyll and vitamins, in the exchange of phosphorus compounds and carbohydrates. Molybdenum is of great importance in the fixation of molecular nitrogen by nodule bacteria.

With a lack of molybdenum, plants lag behind in growth and reduce yields, the leaves become pale in color (chlorosis), and as a result of a violation of nitrogen metabolism, they lose turgor.

Molybdenum starvation is most often observed on acidic soils with a pH less than 5.2. Liming increases the mobility of molybdenum in the soil and its consumption by plants. Particularly sensitive to the lack of this element in the soil legumes. Under the influence of molybdenum fertilizers, not only the yield increases, but also the quality of products improves - the content of sugar and vitamins in vegetable crops, protein in leguminous crops, protein in the hay of legumes, etc. increases.

An excess of molybdenum, like its lack, affects plants negatively - leaves lose green coloring, growth is retarded and crop yields are reduced.

Copper

Copper, like other trace elements, is consumed by plants in very small quantities. There are 2-12 mg of copper per 1 kg of dry weight of plants.

Copper plays an important role in redox processes, having the ability to change from a monovalent form to a divalent one and vice versa. It is a component of a number of oxidative enzymes, increases the intensity of respiration, affects the carbohydrate and protein metabolism of plants. Under the influence of copper, the content of chlorophyll in the plant increases, the process of photosynthesis intensifies, and the resistance of plants to fungal and bacterial diseases increases.

Insufficient provision of plants with copper adversely affects the water-retaining and water-absorbing capacity of plants. Most often, a lack of copper is observed on peat-marsh soils and some soils of light mechanical composition.

At the same time, too high a content of copper available for plants in the soil, as well as other microelements, negatively affects the yield, since the development of roots is disturbed and the intake of iron and manganese into the plant decreases.

Manganese

Manganese, like copper, plays an important role in redox reactions occurring in the plant; it is part of the enzymes by which these processes occur. Manganese is involved in the processes of photosynthesis, respiration, carbohydrate and protein metabolism. It accelerates the outflow of carbohydrates from the leaves to the root.

In addition, manganese is involved in the synthesis of vitamin C and other vitamins; it increases the sugar content in the roots of sugar beets, proteins in cereals.

Manganese starvation is most often observed on carbonate, peat and heavily limed soils.

With a lack of this element, the development of the root system and plant growth slows down, and productivity decreases. Animals fed low manganese diets suffer from weakened tendons and poor bone development. In turn, an excess amount of soluble manganese, observed on strongly acidic soils, can adversely affect plants. Toxic action excess manganese is eliminated by liming.

Zinc

Zinc is part of a number of enzymes, for example, carbonic anhydrase, which catalyzes the breakdown of carbonic acid into water and carbon dioxide. This element takes part in the redox processes occurring in the plant, in the metabolism of carbohydrates, lipids, phosphorus and sulfur, in the synthesis of amino acids and chlorophyll. The role of zinc in redox reactions is less than the role of iron and manganese, since it does not have a variable valency. Zinc affects the processes of fertilization of plants and the development of the embryo.

Insufficient provision of plants with digestible zinc is observed on gravel, sandy, sandy loamy and carbonate soils. Vineyards, citrus and fruit trees in the arid regions of the country on alkaline soils are especially affected by a lack of zinc. With prolonged zinc starvation in fruit trees dry top is observed - the death of the upper branches. Of the field crops, corn, cotton, soybeans and beans show the most acute need for this element.

The disruption of chlorophyll synthesis processes caused by zinc deficiency leads to the appearance of light green, yellow and even almost white chlorotic spots on the leaves.

Cobalt

In addition to all the microelements described above, plants also contain microelements whose role in plants has not been sufficiently studied (for example, cobalt, iodine, etc.). However, it has been established that they are of great importance in the life of humans and animals.

So, cobalt is part of vitamin B 12, with a lack of which metabolic processes are disturbed, in particular, the synthesis of proteins, hemoglobin, etc. is weakened.

Insufficient provision of feed with cobalt at its content of less than 0.07 mg per 1 kg of dry weight leads to a significant decrease in the productivity of animals, and with a sharp lack of cobalt, livestock becomes ill with dryness.

iodine

Iodine is an integral part of the thyroid hormone - thyroxine. With a lack of iodine, the productivity of livestock sharply decreases, the functions of the thyroid gland are disturbed, and it increases (the appearance of goiter). The lowest iodine content is observed in podzolic and gray forest soils; chernozems and serozems are more provided with iodine. In soils of light mechanical composition, poor in colloidal particles, iodine is less than in clay soils.

As shows chemical analysis, plants also contain elements such as sodium, silicon, chlorine, aluminum.

Sodium

Sodium makes up from 0.001 to 4% of the dry mass of plants. Of the field crops, the highest content of this element is observed in sugar, table and fodder beets, turnips, fodder carrots, alfalfa, cabbage, and chicory. With the harvest of sugar beet, about 170 kg of sodium per 1 ha is taken out, and about 300 kg of fodder.

Silicon

Silicon is found in all plants. The largest amount of silicon was noted in cereal crops. The role of silicon in plant life has not been established. It increases the absorption of phosphorus by plants due to the increase in the solubility of soil phosphates under the action of silicic acid. Of all the ash elements, silicon is the most abundant in the soil, and plants do not experience a lack of it.

Chlorine

Plants contain more chlorine than phosphorus and sulfur. However, its necessity for normal plant growth has not been established. Chlorine quickly enters plants, negatively affecting a number of physiological processes. Chlorine reduces the quality of the crop, makes it difficult for the plant to enter anions, in particular phosphate.

Citrus crops, tobacco, grapes, potatoes, buckwheat, lupins, seradella, flax, and currants are very sensitive to the high content of chlorine in the soil. less sensitive to a large number chlorine in soil cereals and vegetable crops, beets, herbs.

Aluminum

Aluminum in plants can be contained in significant quantities: its share in the ashes of some plants accounts for up to 70%. Aluminum disrupts the metabolism in plants, hinders the synthesis of sugars, proteins, phosphatides, nucleoproteins and other substances, which adversely affects plant productivity. The most sensitive crops to the presence of mobile aluminum in the soil (1-2 mg per 100 g of soil) are sugar beet, alfalfa, red clover, winter and spring vetch, winter wheat, barley, mustard, cabbage, carrots.

In addition to the mentioned macro - and microelements, plants contain a number of elements in negligible amounts (from 108 to 10 - 12%), called ultramicroelements. These include cesium, cadmium, selenium, silver, rubidium, and others. The role of these elements in plants has not been studied.
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The role of phosphorus in plant nutrition

Phosphorus is an essential element in plant nutrition. It is part of nucleic acids, membranes, phospholipids. Phosphorus is an element of the energy system, is part of macroergic compounds. As a storage substance is deposited in the seeds of plants. If in mineral nutrition lack of phosphorus, then the activity of photosynthesis, respiration decreases, since the synthesis of chlorophyll is disturbed.

It has long been noted that during the first periods of growth, agricultural crops absorb phosphates more intensively than in subsequent ones. Phosphorus starvation of plants in early period growth imposes such a long-term inhibitory effect that it cannot be completely overcome even by normal subsequent nutrition. Moreover, such cultures that were starving at the beginning of development react negatively to abundant phosphate nutrition in the future.

The problem of phosphorus is becoming one of the most acute in agriculture. This is explained by two main reasons - the lack of geological reserves of this element and its fast and strong binding in the soil when applied with fertilizers. That is why the digestibility of fertilizer phosphorus by agricultural plants does not exceed 25% and its overwhelming amount is fixed by the soil, turning into phosphates that are hard to reach for plants. .

Phosphorus plays an extremely important role in life. It is found in plants in mineral and organic substances.
In the mineral form, phosphorus is in the form of salts of orthophosphoric acid with calcium, magnesium, potassium, ammonium and other cations. Although they are contained in small quantities, they are involved in the formation of many phosphorus-containing organic compounds and are vital for plants. Such organic compounds include nucleic acids, nucleoproteins, phosphoproteins, phosphatides, phytin, sugar phosphates, macroergic and other compounds.

Nucleic acids - ribonucleic (RNA) and deoxyribonucleic (DNA) are complex macromolecular substances involved in the most important life processes: RNA - in the synthesis of proteins specific to a given organism, DNA - in the transfer of hereditary properties and the transfer of biological information.
Nucleic acids with proteins form complex proteins, nucleoproteins, are found in embryonic tissues and the cell nucleus. An important group are phosphoproteins - compounds of protein substances with phosphoric acid. These include enzyme proteins that catalyze many biochemical reactions.

Phosphatides (or phospholipids) are esters of glycerol, fatty acids and phosphoric acid, which, in turn, is associated with other nitrogen-containing organic compounds, such as choline. They contribute to the permeability of various substances into the cell; the seeds of legumes and oilseeds are richer in phosphatides.
Phytin is a derivative of the hexahydric alcohol inositol and is a calcium-magnesium salt of inositol-phosphoric acid. It is contained in all parts and tissues of plants, but mainly in seeds, in the form of a reserve substance (when seeds germinate, phosphoric acid is released, which is used by a young plant).

Sugar phosphates - phosphoric esters of sugars, due to their mobility, play an important role in the processes of photosynthesis, respiration and in the mutual transformations of carbohydrates (sucrose, starch). It is no coincidence that phosphorus is found in small quantities in starch.
An exceptionally large role is played by macroergic compounds containing phosphorus, such as adenosine triphosphoric acid (ATP). This is a kind of energy accumulator and further its supplier (sensor) for many synthetic processes. During the breakdown of ATP, the macro-ergic bond is broken and energy is released, which is many times greater than the energy of hydrolysis of ordinary bonds.

Phosphorus accelerates the maturation of plants. Under its influence, the processes of protein breakdown and the transition of decay products into reproductive organs, into grain. Phosphorus improves the water regime of plants, contributing to a more economical use of water. It is no coincidence that superphosphate provides yield increases not only in conditions of good soil moisture supply, but also with its relative lack in semi-arid years. In addition, good phosphorus nutrition contributes to better overwintering of crops. Phosphorus contributes to the development of the root system, more rapid growth in the first periods of the plant's life (the decay of seed substances and the movement of decay products into the growing parts are accelerated). Therefore, the sowing application of granulated superphosphate in small doses provides a significant increase in the yield of a wide variety of crops.

Phosphorus deficiency affects appearance plants, for example, corn leaves become purple, sugar beet - intense purple, in potatoes the edges of the leaves curl up, the color becomes dark, in tomatoes, a crimson color appears on the underside of the leaves.
Phosphorus fertilizers significantly change the structure of the crop in the desired direction: the share of the most valuable, reproductive part increases. In cereals, the percentage of grain in the total yield increases, in root crops, the yield of roots, etc. The amount of phosphorus in plants is approximately one third of the amount of nitrogen they contain.

In different periods of life, plants consume different amounts of phosphorus. In the initial period after the emergence of seedlings, phosphorus is essential for plants, although in small quantities. The lack of phosphorus at the beginning of plant growth cannot be compensated by its introduction in subsequent periods. Cereals consume the greatest amount of phosphorus in the phases of bobbing and heading, flax - during the flowering period, root crops, potatoes, cabbage use phosphorus more or less evenly throughout the growing season.
In the phase of formation and especially maturation of the reproductive organs in all cultures, there is an energetic movement of phosphates to them from the vegetative parts of the plant.

Phosphorus is one of necessary elements nutrition. In the words of Academician Fersman, "Phosphorus is an element of life and thought." Without it, life is impossible not only for higher plants, but also for the simplest organisms. Phosphorus is a constituent of many substances that play an important role in life phenomena. It is found in nucleic acids (RNA and DNA), i.e. phosphorus takes part in the synthesis of proteins and in the transfer of hereditary properties and biological information. High-energy compounds containing phosphorus, such as ATP, play a very important role. It is the main energy accumulator and its carrier for many synthetic processes. In particular, without ATP, the processes of photosynthesis and respiration will not go on. adenosine diphosphate plant photosynthesis

Phosphorus is a companion of nitrogen; Where there is nitrogen, there is also phosphorus. In plants, it is represented by mineral and organic compounds. Mineral phosphates are present in plant tissues most often in the form of calcium, potassium, and magnesium salts of orthophosphoric acid. Despite the fact that they are usually contained in small amounts, they play an important role in creating a buffer system of cell sap and serve as a reserve for the formation of organic phosphorus-containing compounds. Organic compounds predominate and play the most important role in plants. These include nucleic acids, nucleoproteins, phosphoproteins, phosphatides, phytin, sugar phosphates, macroergic compounds, etc. Among them, nucleic acids should come first. These are complex macromolecular substances that are involved in the most important processes life: RNA (ribonucleic) - in the synthesis of proteins specific to a given organism, DNA (deoxyribonucleic) - in the transfer of hereditary properties and the transfer of biological information. Nucleic acids with proteins form complex proteins, nucleoproteins, which are found in embryonic tissues and cell nuclei. An important group are phosphoproteins - compounds of protein substances with phosphoric acid. These include proteins - enzymes that serve as catalysts for many biochemical processes.

Phosphatides (or phospholipids) play a very important biological role. They form protein-lipid molecules that contribute to the permeability of various substances into the cell. There are phosphatides in any plant cell, but seeds, especially oilseeds and legumes, differ in their highest content.

An important compound is phytin. There is a lot of phytin in young organs and tissues, and especially in seeds, in the form of a reserve substance. When seeds germinate, phosphoric acid is released, which is used by the young plant. In the seeds of legumes and oilseeds, phytin is 1--2% of the weight of the dry mass, in the seeds of cereals - 0.5--1.0%. An important role in the processes of photosynthesis, respiration and in the mutual transformations of carbohydrates (sucrose, starch) is played by sugar phosphates. The content of sugar phosphates in plants varies depending on the age of the plants, their nutritional conditions and other factors and ranges from 0.1 to 1.0% of the dry mass weight. The total content of phosphorus in plants is much lower than that of nitrogen and ranges from 0.3 to 2% (nitrogen - 1 - 5%). Young growing tissues are rich in phosphorus; a lot of it accumulates in the marketable part of the crop (in the generative organs). Phosphorus accelerates the maturation of plants. Under its influence, the processes of protein breakdown and the transition of decay products to the reproductive organs, in particular, to grain, are accelerated in the leaves. Since phosphorus plays an important role in carbohydrate metabolism, phosphate fertilizers contribute to the accumulation of sugars in beets, and in potato tubers - starch. Good phosphorus nutrition contributes to better overwintering of winter crops, fruit and berry crops.

Thus, phosphorus takes the most direct participation in many life processes of plants, and ensuring high level phosphorus nutrition is one of essential conditions obtaining large crop yields. Phosphorus is found in plants in much smaller quantities than nitrogen. It occurs in soil in both mineral and organic forms. Located in organic compounds phosphorus becomes available to plants only after mineralization (decomposition) of organic matter. Salts of orthophosphoric acid H 3 PO 4 are the main source of phosphorus nutrition, although it has been proven that plants can also use salts of other phosphoric acids: metaphosphoric, pyrophosphoric, and others.

Phosphoric acid - tribasic; it can dissociate three anions:

N 3 RO 4 N 2 RO 4 - NRO 4 2- RO 4 3-

pH=5-6 pH=6-7 digestible in an alkaline environment

The most favorable pH for phosphorus availability is close to neutral to slightly acidic. Soils with a slightly alkaline reaction are usually characterized by an abundance of calcium. Under such conditions, phosphorus is converted into sparingly soluble calcium phosphates and phosphorus deficiency usually occurs. Plant availability various salts phosphoric acid depends on their solubility. The most soluble in water are salts of phosphoric acid with monovalent cations of potassium, sodium, ammonium. They are well absorbed by plants:

H 2 RO 4 - + K + \u003d KN 2 RO 4 HRO 4 2- + 2K + \u003d K 2 HRO 4 RO 4 3- + 3K + \u003d K 3 RO 4

Salts of various solubility are formed with divalent cations:

H 2 RO 4 - + Ca 2+ Ca (H 2 RO 4) 2 - monosubstituted calcium phosphate (Ca monophosphate); water-soluble compound (forms the basis of superphosphate)

HPO 4 2- + Ca 2+ CaHRO 4 - disubstituted calcium phosphate (Ca diphosphate); a water-insoluble compound, but soluble in weak acids, including organic ones. Due to the acidity of the soil and root secretions, it is also an important source of phosphorus nutrition (it forms the basis of the precipitate)

RO 4 3- + Ca 2+ Ca 3 (RO 4) 2 - trisubstituted calcium phosphate. A compound insoluble in water and weak acids (forms the basis of phosphorite flour). This compound can be partially dissolved and absorbed only in acidic (not saturated with bases) soil.

With trivalent cations (Al, Fe), phosphates form sparingly soluble compounds (AlPO 4, FePO 4), available to plants only in freshly precipitated form

The amount of dissolved phosphates increases with increasing humidity and, consequently, the provision of plants with phosphorus increases. So, for example, soils with a heavy granulometric composition retain more water than light ones, and therefore contain more phosphorus in solution. A. V. Sokolov notes that in wet years, plants show a lower need for phosphorus and respond less well to the application of phosphorus fertilizers than in dry years. Most plants absorb H 2 RO 4 - more easily than HPO 4 2- .