Potassium and potash fertilizers, the importance of potassium for plants - agrochemistry. The value of potassium for plant growth and development

Potassium, along with nitrogen and phosphorus, are among the main plant nutrients. The function of potassium in plants, as well as other elements necessary for them, is strictly specific. In plants, potassium is in the ionic form. Potassium is found mainly in the cytoplasm and vacuoles of cells. About 80% of potassium is found in cell sap and can be easily washed out with water, especially from old leaves.

IN daytime days, when all biochemical processes are actively taking place in plants, potassium is retained in the cells of the illuminated plant. At night, when the processes of photosynthesis stop, part of the potassium can be released through the roots, so that later, with the advent of the first sunbeam is reabsorbed by the plant.

Young plant organs contain 3-5 times more potassium than old ones, it is more in those organs and tissues where metabolic processes and cell division are intensively going on. The easy mobility of potassium in plants causes its reutilization by moving from old leaves to young ones.

The physiological functions of potassium are very diverse. It has been established that it stimulates the normal course of photosynthesis, enhances the outflow of carbohydrates from leaf blades to other organs, as well as the synthesis of sugars.

Potassium enhances the accumulation of monosaccharides in fruit and vegetable crops, increases the content of sugars in root crops, starch in potatoes, thickens the cell walls of the straw of cereal crops and increases the lodging resistance of bread, and improves fiber quality in flax and hemp.

Promoting the accumulation of carbohydrates in plant cells, potassium increases the osmotic pressure of cell sap and thereby increases the cold resistance and frost resistance of plants.

Potassium is absorbed by plants in the form of cations and, obviously, remains in cells in this form, activating the most important biochemical processes in plant cells, potassium increases their resistance to various diseases, both during the growing season and in the post-harvest period, significantly improves the keeping quality of fruits and vegetables .

Unlike nitrogen and phosphorus, potassium is more in the vegetative organs of plants than in the reproductive ones. For example, in the straw of most cereals there is almost twice as much potassium, and in corn stalks - 5 times more than in grain. Therefore, the removal of K2O with the non-marketable part of the crop, as a rule, is higher than with the marketable part (with the exception of legumes)

Potassium deficiency causes many metabolic disorders in plants, the activity of a number of enzymes is weakened, carbohydrate and protein metabolism is disturbed, and the cost of carbohydrates for respiration increases. As a result, the productivity of plants falls, the quality of products decreases.

Outwardly, potassium starvation manifests itself primarily on the leaves of the lower tier, they turn yellow prematurely, starting from the edges, then the edges turn brown, and then die and collapse, as a result of which they look like burnt, this phenomenon is called "marginal burn". Excessive potassium nutrition of plants also negatively affects their growth and development. It manifests itself in the appearance between the veins of the leaves of pale mosaic spots, which eventually turn brown, and then the leaves fall off.

Thus, by adjusting the level potassium nutrition plants can significantly affect their productivity and the quality of the products obtained.

Such an element as potassium is often underestimated. Perhaps this is due to the fact that it does not actively participate in the "construction", such as nitrogen, and does not enrich plants with energy like phosphorus, and potassium also does not form new organic compounds. But, nevertheless, its role in the full life of plants is simply enormous and, if we translate its meaning into human language, then potassium can be safely called a dispatcher.

The role of potassium in the life of the body:

responsible for the movement nutrients, which come from the soil layer, through the root system into the plant organism.
participates in the formation of new cells, namely, it strengthens their tissues,
enhances the immunity of plant organisms, thereby making them more resistant to various diseases, pests and manifestations of negative environmental factors, for example, return frost spring or thaws in the middle of winter.

The result of insufficient potassium content in the soil

Symptoms of potassium starvation can easily be confused with signs of some kind of disease or a simple manifestation of general plant fatigue or stress. In the early stages, potassium starvation will manifest itself only in the form of a slowdown in plant growth and a decrease in their winter hardiness. However, the whole danger of potassium starvation lies in the fact that it is far from always possible to determine its deficiency in the soil in the early stages, when everything can be corrected quickly.

After the first signs, which are generally harmless, the so-called second stage begins, which manifests itself in the form of more serious phenomena.

With the continuation of potassium starvation, plants appear edge burn, that is, in almost all leaf blades, the tips begin to dry out and turn brown. Such a phenomenon, however, is observed with an acute deficiency of potassium in the soil, but if its amount is not much, but still below the norm, then all you can notice is small bright dots on the surface of adult leaf blades. On young leaves, especially during their active growth, there are clearer signs of potassium starvation - wrinkles near growth points.

With a critical lack of potassium in the soil or when it is completely inaccessible to plants, perhaps the most serious changes are observed - a strong coarsening of leaf blades and the subsequent formation of through holes and breaks at the edges.

Fruits with a lack of potassium most often have an atypical, irregular shape, uncharacteristic, usually unpleasant, taste and become completely unsuitable even for short-term storage.

The result of excess potassium in the soil

As you can see, the lack of potassium is not so noticeable, and this element cannot be considered optional, it must be present in the soil in abundance, but not in excess, because an excess amount of potassium in the soil, although it does not lead to such serious consequences as, say , excess nitrogen, but still exerts Negative influence on plants. First of all, this negative effect manifests itself in the form of an obstacle to the absorption by plants of such trace elements important for normal life as calcium, magnesium and manganese, which can lead to changes in taste, color, dysplasia and other unpleasant things.

How to deposit potash fertilizers into the soil

It is best to apply potash fertilizers to the soil in autumn time, combining with digging the soil on a full shovel bayonet. In greenhouse conditions, fertilizers containing potassium are applied when planting seedlings, as well as during root feeding. Potash fertilizers are usually very soluble in water.

In order not to make a mistake with the choice of fertilizer, it is necessary to know how much potassium is contained in each of them.

So the highest content of potassium (53-59%) is present in potassium chloride. IN matchbox will fit about 18 grams of powder. Potassium chloride is usually added in the fall, so that the chlorine contained in it evaporates.

IN Potassium sulfate the potassium content reaches 52%. In a matchbox of potassium sulfate will fit about 25 grams. Potassium sulfate also contains sulfur in its composition, therefore it is suitable for all crops.

Potassium nitrate contains about 43% potassium. A matchbox will contain a little less than 25 grams of this fertilizer. Due to the presence of nitrogen in the composition, potassium nitrate can be used in protected ground.

Kalimagnesia in its composition contains a little more than 25% potassium. In a matchbox of this fertilizer is placed about 20 grams. Most often, potassium magnesia is used in the form of dressings not only with a deficiency of potassium, but also with a lack of magnesium.

fertilizer such as kalimag rich in potassium by 17-18%. In a matchbox it fits as much as 30 grams.

In addition to these fertilizers, potassium is present in more complex, so-called complex fertilizers, such as nitrophoska, where it is about 17%, nitroammophoska with a potassium content of up to 16% and others.

About the effect of nitrogen on the development of plants and about nitrogen fertilizers read

Read about the effect of phosphorus on plant development and about phosphate fertilizers

Have a rich harvest!

Oddly enough, the main widely available organic fertilizer with potassium it is furnace ash.
The ash contains potash (potassium carbonate). Its amount varies greatly in different types fuel.

Like the ashes of the young deciduous plants contains up to 14% potassium oxide. In old conifers oh its smaller.

Ash can be called complex fertilizer, since, in addition to potassium, it contains phosphorus. The presence of potassium oxide in the ash allows it to be used on soils with high acidity.

The second most important source organic potassium slurry is a nitrogen-potassium fertilizer fast action. It is used mainly as top dressing: it is diluted with water 5–6 times and applied to the soil after preliminary watering in about a day.

Let's go ahead and see what other organic fertilizers contain potassium?

This is a well-known pond and lake silt. Silt is an excellent organic fertilizer with potassium, because in terms of potassium content it is second only to furnace ash. In addition to the source of organic potassium, ash has another 70 substances useful for plants.

Sludge contains up to 30% humus, up to 2% nitrogen, 8% potassium and 5% phosphorus; moreover, the upper layers of silt are richer in nutrients than the lower ones.

lake rich in silt

It contains about 15% of water and 85% of valuable nutrients needed to improve soil fertility - nitrogen, phosphorus, potassium, calcium, manganese, sulfur, boron, copper, zinc, molybdenum.

However, when the straw decomposes, it loses a lot of nitrogen, and some more is washed out of the soil, so it is better to use straw in composts or in the form of straw cutting.

As we can see, the potassium content in it is significantly small compared to the above fertilizers and is no more than 1%.

If you add a large amount of banana peel to it, then the potassium content in the humus will grow and we will get a more valuable substrate. Besides .

In all other cases, potassium is extracted by processing potash ores and natural salts. Sylvinite, langbeinite, and schenite are leaders in potassium content (about 25%).

Potassium in plant life.

Potassium is a substance that plants need to create a strong cell membrane. It is contained mainly in the leaves of the plant, and in its roots it is quite small.

The introduction of this element not only increases the yield of crops, but also improves the quality of fruits and grains. Also, this element takes part in the synthesis of vitamin C; in case of a lack of this vitamin, the fruits lose their color and aroma.

Potash and potash fertilizers Video:

The value of potassium for plants

Potassium is one of the main nutrients, along with nitrogen and phosphorus. The function of potassium in plants, as well as other elements necessary for them, is strictly specific.

The first assumptions about the need for potassium in plants were made by Saussure in 1804 on the basis of the analysis of plant ash, in which potassium was always present. Then Liebig concluded that it was necessary to use potash fertilizers. The first experimental data on the absolute need for potassium in plants were obtained by Salm-Gorstmar in 1846.

Unlike nitrogen and phosphorus, potassium is not a part of organic compounds in plants, but is found in plant cells in ionic form in the form of soluble salts in cell sap and partially in the form of unstable complexes with cytoplasmic colloids.

Potassium is much more in young vital parts and organs of plants than in old ones. About 80% of potassium is in the cell sap and can be easily washed out with water (rain and irrigation). Young plant organs contain 3-5 times more potassium than old ones: there is more of it in those organs and tissues where metabolic processes and cell division are intensive. With a lack of potassium in the nutrient medium, it is outflow from older organs and tissues to young growing organs, where it undergoes reuse(recycling).

The physiological functions of potassium in the plant organism are diverse. He renders positive influence on the physical state of the colloids of the cytoplasm, increases their hydration, swelling and viscosity, which has great importance for normal metabolism in cells, as well as to increase plant resistance to drought. With a lack of potassium and increased transpiration, plants lose turgor faster and wither.

Potassium has a positive effect on the intensity of photosynthesis, oxidative processes and the formation of organic acids in plants, participates in carbohydrate and nitrogen metabolism. With a lack of potassium in the plant, protein synthesis is inhibited, as a result, the entire nitrogen metabolism is disrupted.

Potassium deficiency is especially pronounced when plants are fed with ammonium nitrogen. The introduction of high rates of ammonium nitrogen with a lack of potassium leads to the accumulation in plants of a large amount of unprocessed ammonia, which has a harmful effect on the plant. With a lack of potassium, the transformation of simple carbohydrates into more complex ones (oligo- and polysaccharides) is delayed.

Potassium increases the activity of enzymes involved in carbohydrate metabolism, in particular sucrase and amylase. This explains the positive effect of potash fertilizers on the accumulation of starch in potato tubers, sugar in sugar beets and other root crops. Under the influence of potassium, the frost resistance of plants increases, which is associated with a high content of sugars and an increase in osmotic pressure in cells.

With sufficient potassium nutrition, the resistance of plants to various diseases increases, for example, in grain breads to powdery mildew and rust, in vegetable crops, potatoes and root crops to rot pathogens. Significantly improves the keeping quality of fruits and vegetables. Potassium has a positive effect on the strength of the stems and the resistance of plants to lodging, on the yield and quality of flax and hemp fiber.

The critical period in the consumption of potassium by plants falls on the first 15 days after germination. The period of maximum consumption coincides with the period of intensive biomass growth. The intake of potassium ends in flax by the flowering phase, in cereals and legumes by flowering-milky ripeness. In other crops, the period of potassium intake into plants is more extended, and passes during the entire growing season (potatoes, sugar beets, cabbage).

Relative content of elements mineral nutrition in the main and by-products of various agricultural crops is determined primarily by their species characteristics, but also depends on the variety and growing conditions. The content of nitrogen and phosphorus is much higher in the economically valuable part of the crop - grain, roots and tubers than in straw and tops. Potassium is contained more in straw and tops than in the marketable part of the crop.

Potassium-loving crops (sugar and fodder beets, potatoes, cabbage and corn) consume this element much more than cereals and legumes, flax and grasses. Sunflower also consumes a lot of potassium.

The total removal of potassium with crop yields varies greatly. This is due to the features chemical composition plants, fluctuations in the level of the formed crop and a change in its structure.

Potassium deficiency causes many metabolic disorders in plants. As a result, the productivity of the plant falls, the quality of products decreases, the plants begin to be more often affected by various diseases.

External signs of potassium starvation are manifested in the browning of the edges of leaf blades - `marginal fuse`. The edges and tips of the leaves acquire a `burnt` appearance, small rusty specks appear on the plates. With a lack of potassium, the cells grow unevenly, which causes corrugation, dome-shaped twisting of the leaves. A characteristic bronze coating also appears on the leaves of potatoes. Especially often, a lack of potassium manifests itself in the cultivation of potatoes, root crops, cabbage, silage crops and perennial grasses that are more demanding on this element. Cereals are less sensitive to potassium deficiency. But even with an acute potassium deficiency, they do not bush well, the internodes of the stems are shortened, and the leaves, especially the lower ones, wither even with a sufficient amount of moisture in the soil.

Excessive potassium nutrition of plants also adversely affects their growth and development. It manifests itself in the appearance between the veins of the leaves of pale mosaic spots, which eventually turn brown, and then the leaves fall off. Therefore, an optimally developed potassium nutrition plan for plants will significantly affect the productivity and quality of the crop.

Potassium in the soil

The content of potassium (K 2 O) in different soils ranges from 0.5 to 3% and depends on the mechanical composition. More potassium is contained in the clay fraction of the soil. Therefore, heavy clay and loamy soils are richer in potassium (2-3%) than sandy and sandy loamy soils (1.5-2%). Peaty soils are very poor in potassium (0.03-0.05%). Most loamy soils contain 2–2.5% potassium; much more than nitrogen and phosphorus. Total (gross) potassium contains:

in the composition of primary and secondary minerals (not less than 91%),

in exchange-absorbed (0.5-2%) and non-exchange-absorbed (up to 9%) states,

in the form of salts of soil solution (0.05-0.2%),

in the composition of stubble and root residues, microorganisms (up to 0.05%).

According to the degree of mobility and availability for plants, potassium compounds contained in the soil can be divided into the following main forms.

1. Non-exchange-absorbed (fixed) potassium , which is part of strong aluminosilicate minerals, mainly feldspars (orthoclase, etc.) and micas (muscovite, biotite, etc.). Potassium in feldspars is not readily available to plants. However, under the influence of water and carbon dioxide dissolved in it, changes in environmental temperature and the activity of soil microorganisms, these minerals gradually decompose with the formation of soluble potassium salts. Muscovite and biotite potassium is more available to plants.

2. Exchange-absorbed potassium absorbed by soil colloids is 0.8-1.5% of the total potassium content in the soil. It plays a major role in plant nutrition. The good availability of exchangeable potassium for plants is due to its ability, when exchanged with other cations, to easily pass into a solution from which it is absorbed by plants. When plants assimilate potassium from the solution, new portions of it pass from the absorbed state into the soil solution. With the use of exchangeable potassium, this process slows down more and more, and the remaining potassium is more firmly retained in the absorbed state. The content of exchangeable potassium can serve as an indicator of the degree of provision of the soil with assimilable potassium. Ordinary and thick chernozems and gray soils are richer in exchangeable potassium than soddy-podzolic soils, especially sandy and sandy loamy soils.

3. water soluble potassium It is represented by various salts dissolved in soil moisture (nitrates, phosphates, sulfates, chlorides, carbonates), which are directly absorbed by plants. Its content in the soil is usually insignificant (about 1/10 of the exchange value), since potassium from the solution immediately passes into an absorbed state and is consumed by plants. In some soils, water-soluble potassium (as well as potassium applied to the soil fertilizers) can be absorbed in a non-exchangeable form, as a result, its availability to plants is reduced. The non-exchange fixation of potassium, as well as the ammonium ion, is most pronounced in chernozems and gray soils, especially when they are alternately moistened and dried.

Between various forms potassium in soils there is a mobile balance. The amount of water-soluble forms of potassium can be replenished at the expense of exchange-absorbed ones, the decrease in which after some time can be compensated for by the fixed form. It should be borne in mind that when water-soluble potash fertilizers are applied, their transformation can proceed in the opposite direction. Part of the potassium is lost from the root layer due to infiltration (the process of seepage and soaking) from 2% on heavy and up to 5% on light soils of the amount of fertilizer applied. Losses can also occur from water or wind erosion.

Therefore, the main condition for maintaining an optimal balance of nutrients in the soil, including potassium, is the compensation of expenses through the use of mineral and organic fertilizers.

Nikolai Vishensky

Potassium, along with nitrogen and phosphorus, is one of the main plant nutrients. It is, of course, necessary for all plants, animals and microorganisms. Attempts to replace potassium with elements close to it (sodium, lithium, rubidium) were unsuccessful. Function of potassium in plants. as well as other elements necessary for them, is strictly specific.

For the first time, the assumption about the need for potassium in plants was made by Sausur in 1804 on the basis of the analysis of plant ash, in which potassium was always present. Then Liebig concluded that it was necessary to use potash fertilizers. The first experimental data on the absolute need for potassium in plants were obtained by Salm-Gorstmar in 1846.

In plants, potassium is in the ionic form. Until now, not a single organic compound is known, which would include this element. Potassium is found mainly in the cytoplasm and vacuoles of cells; it is absent in nuclei and plastids.

About 80% of potassium is found in cell sap and can be easily washed out by water (eg rain), especially from old leaves. In the daytime, when all biochemical processes are actively taking place in plants, potassium, while maintaining easy mobility, is nevertheless retained in the cells of the illuminated plant. At night, when the processes of photosynthesis cease, part of the potassium can be released through the roots, so that later, with the advent of the first sunbeam, it can be reabsorbed by the plant.

Approximately 20% of potassium is retained in plant cells in an exchange-absorbed state by cytoplasmic colloids, and up to 1% of it is non-exchangeably absorbed by mitochondria.

Young plant organs contain 3-5 times more potassium than old ones: there is more of it in those organs and tissues where metabolic processes and cell division are intensively going on. Therefore, potassium is sometimes called the element of youth. A lot of potassium in the pollen of plants. Corn pollen ash contains up to 35.5% potassium, while calcium, magnesium, sulfur and phosphorus combined - only 24.7%. The easy mobility of potassium in plants causes its reutilization by moving from old leaves to young ones. Therefore, its distribution in plants is characterized by a basipeptal concentration gradient, that is, its content in leaves and parts of the stem, calculated per unit of dry matter, increases from bottom to top.

The physiological functions of potassium are very diverse. It has been established that it stimulates the normal course of photosynthesis, enhances the outflow of carbohydrates from the leaf blade to other organs, as well as the synthesis of sugars and high-molecular carbohydrates - starch, cellulose, pectin, xylans.

Potassium enhances the accumulation of monosaccharides in fruit and vegetable crops, increases the content of sucrose in root crops, starch in potatoes, thickens the cell walls of the straw of cereal crops and increases the resistance of bread to lodging, and improves fiber quality in flax and hemp.

Promoting the accumulation of carbohydrates in plant cells, potassium increases the osmotic pressure of cell sap and thereby increases the cold resistance and frost resistance of plants.

Accumulating in chloroplasts and mitochondria, potassium stabilizes their structure and promotes the formation of ATP. Potassium increases the hydrophilicity of protoplasmic colloids; at the same time, transpiration is reduced, which helps plants to better tolerate short-term droughts.

Potassium plays an important role in the synthesis and renewal of proteins in plants. With its deficiency, protein synthesis is sharply reduced and at the same time the decay of old protein molecules occurs. Plants accumulate soluble nitrogen compounds (free amino acids). Improvement in potassium nutrition is accompanied by an increase specific gravity protein nitrogen in wheat plants. The synthesis of amides (asparagine and glutamine) is also enhanced. The positive effect of potassium on protein synthesis is apparently associated, firstly, with its effect on the accumulation and transformation of carbohydrates (and the latter, as is known, give keto acids during respiration - the material for building amino acids) and, secondly, with increased under the influence of potassium activity of enzymes involved in protein synthesis.

Potassium is absorbed by plants in the form of a cation and, obviously, in this form remains in the cell, forming only weak bonds with its substances. In this form, potassium is the main counterion for neutralizing the negatively charged components of the cell, and also creates a difference in electrical potentials between the cell and the environment. Perhaps this is where the specific function of potassium as an indispensable nutrient is manifested.

By activating the most important biochemical processes in plant cells, potassium increases their resistance to various diseases both during the growing season and in the post-harvest period, and significantly improves the keeping quality of fruits and vegetables.

The critical period in the consumption of potassium by plants falls on the first 15 days after germination. The period of maximum consumption, as a rule, coincides with the period of intensive growth of biological mass. In some plants, the intake of potassium ends already by the phase of full flowering (flax) or by flowering - the beginning of milky ripeness (cereals and legumes). In other plants, it is more extended and occurs throughout the growing season (potato, sugar beet, cabbage).

Unlike nitrogen and phosphorus, potassium is more in the vegetative organs of plants than in the reproductive ones. For example, in the straw of most cereals there is almost 2 times more potassium, and in corn stalks - 5 times more than in grain. Therefore, the removal of K2O with the non-marketable part of the crop, as a rule, is higher than with the marketable part (with the exception of legumes).

Potassium-loving crops - sugar and fodder beets, potatoes, vegetables - consume this element much more than cereals and leguminous crops, flax and perennial herbs. Sunflower also consumes a lot of potassium. In the ratio N: P: K, potassium predominates in potassium-philes (2.5-4.5: 1: 3.5-6), and in cereal crops - nitrogen (2.5-3: 1: 1.5-2, 2).

Potassium deficiency causes many metabolic disorders in plants: the activity of a number of enzymes is weakened, carbohydrate and protein metabolism is disturbed, and the cost of carbohydrates for respiration increases. As a result, the productivity of plants falls, the quality of products decreases. In cereals, a feeble grain is formed, the germination and viability of seeds are reduced. Often, due to a deterioration in the strength of the straws of bread, they lie down. The content of starch in potato tubers, sucrose in sugar beet root crops, pectin substances in fruits and berries decreases. The yield of grain, fruit and vegetable crops is falling, the content of vitamins in products is decreasing. With a deficiency of potassium, the susceptibility of plants to various diseases increases.

Outwardly, potassium starvation of plants manifests itself primarily on the leaves of the lower tier: they turn yellow prematurely, starting from the edges; in the future, the edges turn brown, and then die off and collapse, as a result of which they look like burnt ones. This phenomenon is called "marginal burn". Potassium deficiency also affects the decrease in turgor, the leaves wither and droop. Most often, potassium deficiency manifests itself during the period of intensive plant growth (in the middle of the growing season), when its content in plant cells decreases by 3-5 times compared to the norm.

Potassium-loving crops suffer more from a lack of potassium.

Excessive potassium nutrition of plants also negatively affects their growth and development. It manifests itself in the appearance between the veins of the leaves of pale mosaic spots, which eventually turn brown, and then the leaves fall off.

Thus, by regulating the level of potassium nutrition of plants, one can significantly influence their productivity and the quality of the products obtained.

Circulation and balance of potassium in agriculture

Potassium is one of the main biogenic elements. Its circulation in biocenoses is very intense. The content of potassium in the biomass of various biocenoses ranges from 20 (desert) to 2000 kg/ha (oak forests).

The closed cycle of nutrient cycling in natural biocenoses and the accumulating activity of plants lead to the redistribution of potassium within the root layer of the soil and the gradual enrichment of its upper horizons with this element.

In agrocenoses, the cycle and balance of potassium depend mainly on economic activity land users: availability of fertilizers, specialization of farms, etc.

Gross reserves of potassium in soils are many times (5-50) higher than nitrogen and phosphorus. This cannot be ignored.

Part of the potassium is lost from the root layer of the soil due to infiltration: on light soils, about 5%, on heavy soils, about 2% of the amount of fertilizer applied. The intensity of this process is influenced by the granulometric composition of the soil and its water regime, fertilizer doses, and crop characteristics.

Part of the soil potassium is lost as a result of water and wind erosion. According to averaged data, this is 4-8 kg/ha. It is usually believed that the expense items of potassium losses from erosion are compensated by its supply with seeds (about 2 kg/ha) and precipitation (2-6 kg/ha).

It should be borne in mind that some part of the exchangeable potassium can pass in the soil into a fixed (non-exchange-absorbed) state and, thereby, be withdrawn from the potassium fund available to plants. It has also been established that not only arable, but also sub-arable soil horizons take part in the supply of plants with potassium. Thus, the consumption of potassium from the arable layer is reduced. For example, in experiments on soddy-podzolic soils, sunflower and lupine, on average, consumed about 32% of potassium from its total removal from subsurface horizons.

Composition and properties of potash fertilizers

Industrial potash fertilizers are divided into concentrated (potassium chloride, potassium sulfate, potassium chloride - electrolyte, potassium salt, potassium magnesia, potassium-magnesium concentrate) and raw (sylvinite and kainite).

Raw potassium salts.

Obtained by crushing and grinding natural potassium salts. Usually, more concentrated reservoir layers are used for this purpose. It is advisable to use raw potash salts only near potash ore deposits, since they have a low K2O content and a large amount of impurities. They contain a lot of chlorine, which also limits their use.

Of the raw potassium salts, sylvinite and kainite are the most common.

Silvinite - pKS1 + mNaCl. Contains 12-15% K2O and 35-40% ^2O. Available in coarse grinding (crystal size 1-5 mm or more). Pinkish-brown with inclusions of blue crystals. When stored in a humid room, it becomes damp, and when dried, it becomes caked. Transported in bulk. Apply under sodium-loving cultures.

Cainite - KO. MgSO4.3H2O with impurity No. 0. Contains 10% K2O, 6-7% MgO, 32-35% a, 22-25% N2O, 15-17% SO4. These are large pinkish-brown crystals. Humidity is not more than 5%. Obtained by grinding kainite or kainite-langbeinite ore. Does not cake, transported in bulk (bulk).

Concentrated potash fertilizers. Potassium chloride, potassium chloride - KO. This is the main potash fertilizer. Its production is 80-90% of total production potash fertilizers. Potassium chloride is obtained mainly from sylvinite, which is a mixture (agglomerate) of sylvin (KO) and halite (No. 0), containing 12-15% K2O. Chemically pure chloride contains 63.1% K2O. Depending on the production method, potassium chloride supplied agriculture, contains from 57 to 60% K2O. It is a fine crystalline powder of pink or white color with a grayish tint.

Potassium chloride is produced in several ways. The resulting white fine-crystalline potassium chloride during storage strongly caking.

The production waste contains up to 95% No. 0 and serves as a material for the production of soda, industrial table salt.

Flotation potassium chloride has larger natural crystals Pink colour. Hydrophobic additives (fatty amines) used in the flotation process significantly reduce the hygroscopicity and caking of the fertilizer.

This method of production of potassium chloride is the most widely used.

Potassium sulfate - K2SO4. It is a highly concentrated non-chlorine fertilizer. Contains 46-50% K2O. Fine-crystalline powder of white color with a yellow tint, humidity 1.2%. Does not cake, transported in bags or in bulk (without containers). It is obtained in the process of complex processing of polymineral potash ores (langbeinite, schenite) by conversion (exchange decomposition) with potassium chloride, and also as a by-product of a number of chemical industries.

Compared to chlorine-containing potash fertilizers, K2SO4 provides a significant increase in the yield of grapes, buckwheat, tobacco and other chlorophobic crops. This fertilizer is widely used in vegetable growing, especially in greenhouses. The presence of sulfur in the fertilizer has a positive effect on the productivity of cruciferous, legumes and some other crops.

However, the cost of potassium sulfate is much higher than that of all other potash fertilizers.

Potassium magnesia, potassium-magnesium sulfate - K2SO4. MgSO4. Contains 29% K2O and 9% MgO. Obtained by recrystallization from natural sulfate salts, mainly from shenit. Therefore, this fertilizer is sometimes called chenite. White, highly dusty powder with a grayish or pinkish tinge or grayish-pink granules irregular shape. Does not cake, transported in bags or in bulk. It is used primarily for crops sensitive to chlorine or on light soils.

Kalimag, potassium magnesia concentrate - K2SO4. 2MgSO4. It is obtained from sulfate potassium-magnesium-containing minerals by enriching them. Contains 18-20% K2O and 8-9% MgO. Produced in the form of granules gray color. Does not cake, transported in bulk. In terms of efficiency, it approaches potassium magnesia.

Potassium chloride electrolyte - KO with impurities No. 0 and MgCl2. It is a by-product in the production of magnesium from carnallite. Contains 34-42% KA, 5% MgO and No. 2O and up to 50% a. Highly dusty fine crystalline powder with a yellow tint. It does not cake, it is transported in paper bags or in bulk. In terms of efficiency, it approaches potassium chloride; on soils poor in magnesium, it is more effective than KO.

cement dust. Waste of cement production, non-chlorine potash fertilizer. Contains from 10-15 to 35% K2O. Potassium is found in the form of carbonates, bicarbonates, sulfates and a small amount of silicates. There are also gypsum, calcium oxide, sesquioxides and some trace elements. Potassium salts of cement dust are soluble in water and available to plants. It is used as the main fertilizer, primarily on acidic soils ah and under chlorophobic cultures.

Furnace ash. Local potash-phosphorus-lime fertilizer. Potassium is found in the ashes in the form of potash (K2CO3). The content of K2O in the ash varies significantly depending on the fuel source. For example, hardwood ash contains 1014% K2O, 7% P2O5, 36% CaO, softwood ash - 3-7% K2O, 2.0-2.5% P2O5 and 25-30% CaO. When burned, young trees produce more ash, in which the content of nutrients is higher. Furnace ash - enough effective fertilizer for all crops (especially for chlorophobic ones) and for all soils (primarily for acid ones).

Interaction of potash fertilizers with soil

Potash fertilizers are highly soluble in water. When introduced into the soil, they dissolve in the soil solution, and then interact with the soil absorbing complex according to the type of exchange (physico-chemical), and partially non-exchange absorption.

The exchange absorption of potassium cations by the soil is a small part of the total absorption capacity. The reaction of the exchange absorption of potassium cations by the soil is reversible.

As a result of the transition of potassium into an exchange-absorbed state, its mobility in the soil is limited and leaching beyond the arable layer is prevented, except for light soils with low absorption capacity. The exchangeable potassium of fertilizers absorbed by the soil is well available to plants.

Secondary processes of interaction of the soil solution with the soil absorbing complex gradually displace potassium cations from it. takes an active part in this exchange root system plants through root secretions.

On acidic and strongly acidic soils (especially those with a light granulometric composition), which have exchangeable hydrogen and aluminum in the composition of the FPC, a noticeable acidification of the soil solution is observed when potash fertilizers are applied. Therefore, on such soils, the effectiveness of potash fertilizers is reduced.

In addition, additional acidification of the soil solution also occurs due to the manifestation of the physiological acidity of potassium salts. However, it should be noted that the physiological acidity of potassium fertilizers is much less than that of ammonium fertilizers, and it manifests itself, as a rule, only with prolonged use of these fertilizers for potassium-loving crops that consume a large amount of potassium.

Non-exchangeable (fixed) potassium has a much lower mobility than exchange-absorbed. Its transition into solution and its availability to plants are significantly hampered.

Potassium Fixation Fertilizer different soils depending on their mineralogical composition and the dose of fertilizers, it can be from 14 to 82% of the applied amount.

When coarse-grained or granular fertilizers were applied, potassium fixation by the soil decreased by 20-30% due to less contact of the fertilizer with the soil.

The amount of non-exchangeable absorption of potassium also depends on the dose of fertilizer applied. The absolute amount of fixed potassium increases sharply with an increase in the dose of potash fertilizers, although in percentage to the introduced dose, a decrease in fixation is observed. Potential capacity of the soil to fix potassium is very high.

With the systematic use of potash fertilizers and a positive balance of potassium (i.e., when the applied potassium of fertilizers exceeds its removal by plants), the content of both mobile forms of potassium (water-soluble and exchangeable) and its fixed forms increases in the soil.

Under conditions of potassium fertilizer deficiency (i.e., with a negative potassium balance), the reverse process occurs. As plants consume available forms of potassium (water-soluble and exchangeable), a gradual transition of fixed potassium, and partly potassium of the crystal lattice, into more mobile forms occurs. For example, in an experiment on loamy soil (England) for 101 years, plants carried out with yields 3-4 times more potassium than it was contained in the soil in the exchange form.

The use of potash fertilizers on various soils

In areas where potash fertilizers are effective, they provide an increase in yield per kilogram of potassium fertilizers applied: grain 2-3 kg, potatoes 2033, sugar beet 35-40, flax fiber 1-1.5, hay seeded grasses 20-33 and hay meadow grasses 8-18 kg.

The effectiveness of potash fertilizers depends on the soil and climatic conditions and the biological characteristics of cultivated crops.

As for soil factors, here the main one is the provision of soils with potassium available to plants (the sum of water-soluble and exchangeable potassium).

The use of potash fertilizers is most effective on sandy, sandy loam, soddy-podzolic, peat-bog and floodplain soils, as well as on red soils. Potassium fertilizers also have a positive effect on plant yields in the zone of sufficient moisture on loamy soddy-podzolic, gray forest soils, podzolized and leached chernozems (in cases of low and medium availability of potassium).

On typical, ordinary, southern chernozems, chestnut soils and gray soils, the effect of potash fertilizers in most cases is weak or does not appear at all. The use of potash fertilizers is justified under these conditions only for potassium-loving crops - sugar beet, sunflower, vegetables, as well as on chestnut soils and gray soils during irrigation.

On solonetzes, which are usually rich in potassium, potassium fertilizers are not used, since they increase the alkalinity of these soils and do not give the expected effect.

Potash fertilizers, as a rule, have a positive effect on plant yields when the content of mobile potassium in the soil is at the level of 1-3 classes. With a higher supply of soils with potassium, the effectiveness of potash fertilizers decreases and is mainly determined by the composition of the crop rotation crops, the level of applied doses of nitrogen and phosphate fertilizers and other agricultural activities.

The main principles for optimizing the use of potash fertilizers are as follows.

The use of potash fertilizers, taking into account the availability of soils with potassium, the granulometric composition of soils, the biological characteristics of agricultural plants and the forms of potash fertilizers.
Raising the general level of agricultural culture, soil cultivation, maintaining a balanced nutrition of plants with potassium and other nutrients (primarily nitrogen and phosphorus).

The effectiveness of potash fertilizers (as well as phosphorus and nitrogen fertilizers) on slightly acidic and neutral soils increases markedly in comparison with strongly acidic soils.

Therefore, liming acidic soils is one of the mandatory methods for increasing the efficiency of potash fertilizers. However, due to the antagonism of potassium and calcium ions on limed soils, there is a need to increase the doses of potassium fertilizers.

The use of manure, which itself is good source potassium for plants, as a rule, reduces the effect of mineral potassium fertilizers.

The highest efficiency of potash fertilizers is achieved with their optimal ratio with nitrogen and phosphorus. Unilateral application of potash fertilizers is possible on drained peatlands and peat-bog soils provided with other nutrients.

The range of potash fertilizers is dominated by chlorine-containing forms. On soils of medium and heavy granulometric composition, it is advisable to apply such fertilizers in full dose (with the exception of a small dose in rows for some crops) in the fall. At the same time, fertilizers are placed in a more humid soil layer, where the bulk of the roots develop, and they are better absorbed by plants, and chlorine is washed out by autumn-spring precipitation from the arable layer and does not have a negative effect on chlorophobic crops. Only on light, as well as on peat-bog and floodplain soils, potash fertilizers should be applied in the spring. Under tilled and vegetable crops in such cases, it is advisable to give part of the total dose of potassium as a top dressing.

In crop rotation, potash fertilizers are primarily applied under potash-loving crops, which at the same time give a more noticeable increase in yield.

Flax and hemp require relatively little potassium, but their weak root systems cannot provide these plants with sufficient potassium under normal conditions. Therefore, under these crops, increased doses of potash fertilizers should be applied.

Under chlorophobic crops, it is advisable to use fertilizers with a minimum chlorine content. Experiments with potatoes have shown that the use of chlorine-containing potash fertilizers reduces the amount of starch by 7-15% compared to fertilizers that do not contain chlorine.