Why lime soils (part 2)
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Calcium in plant nutrition
The effect of increased soil acidity depends not only on the characteristics of plants, but also on the composition and concentration of other cations in the soil solution, on the total content of nutrients and other properties of the soil. With a lack of calcium, as a nutrient for plants, leaf growth is inhibited. Light yellow spots appear on them (chloroticity), then the leaves die off, and the previously formed (with the previous optimal calcium supply) leaves remain normal.
Unlike magnesium, old leaves contain more calcium than young ones, since it cannot be reused in plants. As the leaves age, the amount of calcium in them increases. Therefore, all the calcium that enters the soil returns with fallen leaves, tops or manure. Calcium enhances the metabolism in plants, plays an important role in the movement of carbohydrates, affects the conversion of nitrogenous substances, accelerates the breakdown of storage proteins in the seed during their germination. In addition, it is essential for the construction of normal cell walls and for the establishment of a favorable acid-base balance in plants.
Calcium in plants is in the form of salts of pectic acid, sulfate, carbonate, phosphate and calcium oxalate. A significant part of it in plants (from 20 to 65%) is soluble in water, and the rest can be extracted from the leaves by treatment with weak acids. It enters plants during the entire period of active growth. In the presence of nitrate nitrogen in the solution, its penetration into plants increases, and in the presence of ammonia nitrogen, due to antagonism between Ca2 + and NH4 + cations, it decreases.
Hydrogen ions and other cations interfere with the intake of calcium at their high concentration in the soil solution. Different plants differ dramatically in the amount of this element consumed. With high yields, agricultural crops carry it in the following quantities (in grams of CaO per 1 m²): cereals - 2-4, legumes - 4-6; potatoes, lupines, corn, beets - 6-12; perennial legumes - 12-25; cabbage - 30-50. Most of all calcium is consumed by cabbage, alfalfa and clover. These crops are also characterized by a very high sensitivity to increased soil acidity.
However, the need of plants for calcium and their ratio to soil acidity do not always coincide. So, all grain breads absorb little calcium, but differ sharply in their sensitivity to an acidic reaction - rye and oats tolerate it well, while barley and wheat do not. Potatoes and lupines are not sensitive to high acidity, but they consume relatively high amounts of calcium. Unlike magnesium, calcium is found less in seeds and much more in leaves and stems. Therefore, most of the calcium taken by plants from the soil is not alienated, but through the feed and litter it enters the manure and returns with it to the summer cottages.
The loss of calcium from the soil occurs not so much as a result of its removal with crops, but as a result of leaching. The loss of this element from the soil greatly increases with acidification. 10-50 g of CaO is washed out annually from 1 m². Five years later, by the time of re-liming, taking into account the annual removal of calcium by plants (20-50 g / m²), there is practically no lime in the soil applied at a dose of 400-600 g / m². On calcium-poor acidic sandy and sandy loam soils when cultivating cabbage, alfalfa, clover, fruit and berry crops, there may be a need for its introduction not only to neutralize acidity, but also to improve their nutrition with this element.
Magnesium in plant nutrition
It plays an important role in plant life. It is part of the chlorophyll molecule and is directly involved in photosynthesis. However, chlorophyll contains a smaller part of this element, about 10% of the total content in plants.
Magnesium is also a part of pectin substances and phytin, which accumulates mainly in seeds. With a lack of magnesium, the chlorophyll content in the green parts of the plant decreases. The leaves, especially the lower ones, become spotty, "marbled", turn pale between the veins, and along the veins the green color is still preserved (partial chlorosis). Then the leaves gradually turn yellow, curl off the edges and fall off prematurely. As a result, the development of plants slows down and their growth deteriorates.
Magnesium, together with phosphorus, is found mainly in the growing parts and seeds of plants. Unlike calcium, it is more mobile and can be reused in plants. From old leaves, magnesium moves to young ones, and after flowering, it flows out of the leaves into the seeds, where it is concentrated in the embryo. There is more magnesium in the seeds, and in the leaves there is less than calcium. The lack of magnesium affects the yield of seeds, roots and tubers more sharply than that of straw or tops. This element plays an important role in various life processes, it participates in the movement of phosphorus in plants, activates some enzymes (for example, phosphatase), accelerates the formation of carbohydrates, and affects the redox processes in plant tissues.
A good supply of plants with magnesium helps to enhance the reduction processes in them and leads to a greater accumulation of reduced organic compounds - essential oils, fats, etc. With a lack of magnesium, on the contrary, oxidative processes intensify, the activity of the peroxidase enzyme increases, and the content of sugar and ascorbic acid decreases.
The magnesium requirement of individual plants is different. With high yields, they consume from 1 to 7 g of MgO per 1 m². The greatest amount of magnesium is absorbed by potatoes, beets, legumes and legumes. Therefore, they are most sensitive to the lack of this element. Many crops on acidic soils (legumes, cabbage, onions, garlic) lack magnesium and calcium as nutrients, most of all due to antagonism with hydrogen, aluminum, manganese and iron, which are very abundant in acidic soils. There is less magnesium in soils than calcium. Especially poor in them are strongly podzolized acidic soils of light texture. In such soils, the application of lime fertilizers containing magnesium significantly increases the yield.
Regular liming of the soils of the summer cottage, on average once every five years, with one of the following fertilizers provides a radical improvement in acidic soils, increases their fertility and improves plant nutrition.
Limestone and dolomite flour
Obtained by grinding and crushing limestone and dolomite. The speed of interaction with the soil and the effectiveness of ground limestone and dolomite are highly dependent on the degree of grinding. Particles larger than 1 mm dissolve poorly and very weakly reduce the acidity of the soil. The finer the grinding, the better they mix with the soil, dissolve faster and more completely, the faster they act and the higher their effectiveness.
Burnt and slaked lime
When firing hard limestones, calcium and magnesium carbonates lose carbon dioxide and turn into calcium oxide or magnesium oxide CaO and MgO. When they interact with water, calcium or magnesium hydroxide is formed, that is, the so-called slaked lime - "fluff". It is a fine crumbling powder of Ca (OH) 2 and Mg (OH) 2. You can extinguish burnt lime directly in the field, sprinkling it with damp earth.
The fastest-acting lime fertilizer, especially valuable for clay soils. It dissolves much better in water (about 100 times) than carbon dioxide, but magnesium hydroxide Mg (OH) 2 is almost insoluble in water. In the first year after application, the efficiency of slaked lime is higher than that of carbonic lime. In the second year, the difference in their effect is largely smoothed out, and in subsequent years, their effect is leveled. According to the ability to neutralize soil acidity, 1 ton of Ca (OH) 2 is equal to 1.35 ton of CaCO3.
Calcareous tuffs (key lime)
They usually contain 90-98% CaCO3, and a small amount of mineral and organic impurities. Their deposits are most often found in near-terrace floodplains, in the places where the keys exit. In appearance, calcareous tuffs are a loose, porous, easily crumbling gray mass, in some cases colored with an admixture of iron hydroxide and organic matter in dark, brown and rusty colors of varying intensity.
Drywall (lake lime)
Contains 80-95% CaCO3, its deposits are confined to the places of dry closed reservoirs, which in the past received water rich in calcium. Lacustrine lime has a fine-grained constitution, easily crumbles and crushes, mainly into particles less than 0.25 mm. Its moisture capacity is small, it does not smudge and retains good flowability.
Contains from 25 to 50% CaCO3, some MgCO3 and other impurities. It is a rock in which calcium carbonate is mixed with clay, and often with clay and sand.
It is low-lying peat rich in lime. Contains CaCO3 from 10-15 to 50-70%. Valuable peat-lime fertilizer, most suitable for liming acidic soils, poor in organic matter and located near the places of occurrence of peat tufts.
Natural dolomite flour
Contains 95% CaCO3 and MgCO3. This is a free-flowing mass of fine texture, 98-99% consists of particles less than 0.25 mm, sometimes there are pieces of hard rock in it, which must be sifted out before introduction. This is a very valuable lime fertilizer, as it contains magnesium in addition to calcium.
It is obtained by burning oil shale at industrial enterprises and power plants, contains 30-48% CaO and 1.5-3.8 MgO and has a significant neutralizing ability. In addition, it includes potassium, sodium, sulfur, phosphorus, and some trace elements. This is the reason for the high efficiency of oil shale ash. Most of the calcium and magnesium in it is in the form of silicates, which are less soluble than carbonates, therefore, in comparison with calcium carbonate, it reduces the acidity of the soil somewhat weaker and slower. However, this does not diminish its value, and for some crops (flax, potatoes, etc.) it is a favorable property.
Read the third part of the article: 11 conditions for the use of lime fertilizers →
G. Vasyaev, Associate Professor,
Chief Specialist of the North-West Scientific and Methodological Center of the Russian Agricultural Academy,
O. Vasyaeva, amateur gardener
Potassium chloride KCl
The content of the main element in the composition of this representative of the group of potash fertilizers reaches 50%. It is used in the fall, for digging, introducing into the soil at the rate of 20-25 gr. per m², since chlorine is washed into the deeper layers of the soil, and its effect on plants is minimized.
Potassium chloride is especially good for potatoes, beets, barley, and most cereals.
KCl is a mineral fertilizer with a high concentration of nutrients per gram, acidic, soluble in water.
The average rate of its application for all vegetables and cereals is about 2 centners per hectare. If it is planned to plant sugar-containing crops on the prepared soil, then the dose can be increased by 25-50%.
Potassium sulfate K2SO4
Another name for this element is potassium sulfate. The great content of this element makes it the best mineral fertilizer for plants experiencing severe K.
It does not contain any impurities such as chlorine, sodium and magnesium.
Potassium sulfate is an ideal fertilizer for cucumbers, especially during the period of ovary and fruit formation, since it contains about 46% of potassium, so beloved by these melons and gourds.
Application rates for spring digging are about 25-30 g / m², for root dressing - 10 g / m².
Potassium salt (KCl + NaCl)
The main two components of this mineral fertilizer are chlorides. The substance looks like crystals of an auburn color.
In modern agro-industrial complexes, sylvinite is most often used - one of the most successful forms of potassium salt.
In the spring, this fertilizer is applied for all types of berry crops, at the rate of 20 grams. under one bush. In autumn, it is spread over the soil surface before plowing. The rate of continuous application of potash salt is 150-200 g / m².
How to Replenish Nitrogen Deficiency in Plants
In the soil
Nitrogen for plant nutrition is applied in the form of: potassium, sodium nitrate, ammonium, organic and other fertilizers. They increase the yield of almost all crops.
The soil is fertilized in early spring and early summer. During this time, the plant develops most actively. Timely feeding stimulates metabolism and stimulates growth.
Fertilizers have a positive effect after spring frosts and temperature drops. And it is not recommended to make them after the middle of summer. This will prolong the growth and significantly reduce the winter hardiness of the plants. Accumulation of nitrates in fruits is also possible.
What soils require liming
Before you start improving the fertility on your site, you have to find out whether the soil actually has acidity, and for effective fertilization, first of all, the correct calculation of the amount of lime per volume of the fertilized soil complex is necessary. And the very need for liming should be established, in an amicable way, on the basis of special agrochemical analyzes. The calculated dose of lime material will depend on the acidity of the soil and the presence of humus in it.
In general, to the question of which soils require liming, it must be remembered that they have an increased level of acidity:
- red earth soils,
- sod-podzolic soils,
- gray forest,
- peat bog.
For acidic soils, a whitish tint is characteristic, and when digging a site, layers of the same color are noticeable. At the same time, acidic soil is not necessarily evenly distributed throughout the entire site, but can only be in some places. Most likely, if mint and sorrel, horsetail and plantain, ivan-da-marya and heather grow violently on the site, soils with high acidity prevail on it.
The role of macro- and microelements in plant nutrition
Almost all elements of the periodic system of D.I. Mendeleev, but the role of many of them is still insufficiently understood.
Plants absorb nitrogen, phosphorus, potassium, calcium, magnesium, sulfur in the greatest quantity. These elements are called macronutrients, their content in plants is calculated in whole percentages or tenths.
Nitrogen (N) is a part of all proteins, nucleic acids, amino acids, chlorophyll, enzymes, many vitamins, lipoids and other organic compounds formed in plants. Lack of nitrogen causes the cessation of growth and yellowing of the leaves due to the violation of chlorophyll formation.
Nitrogen is a very mobile element; if it is deficient, it moves from old leaves to new, younger ones. Signs of nitrogen starvation appear - first in the yellowing of the lowest leaves, and then, if the process is not stopped, in the death of the leaves above.
Excess nitrogen leads to unnaturally rapid growth, the formation of loose tissues, which makes them more susceptible to various diseases. The growing season is lengthened and the beginning of flowering is delayed; in some plants, an overdose of nitrogen fertilizers can shift internal processes so much that it will lead to a complete rejection of flowering. Excess nitrogen also delays the absorption of potassium by the plant.
Phosphorus (P) plays an extremely important role in plant life.Most metabolic processes are carried out only with his participation. It ensures the health of the roots, the laying of buds, the ripening of fruits and seeds, and increases winter hardiness.
With a lack of phosphorus, flowering and ripening are delayed, defective fruits are formed, the leaves acquire a reddish-brown tint. First of all, the old lower leaves are affected, then the process spreads higher.
Excess phosphorus slows down metabolism, makes the plant less resistant to lack of water, impairs the absorption of iron, potassium and zinc, which leads to general yellowing, chlorosis, the appearance of bright necrotic spots, and leaf fall. The development of the plant is accelerating, it ages quickly.
Some plants react particularly negatively to high doses of phosphate fertilizers. This applies primarily to people from Australia, where the soil is poor in phosphorus. Conifers do not like feeding with phosphorus. Hibiscuses also require special care when introducing this element, for which it is not recommended to use fertilizers rich in phosphorus for flowering plants.
Potassium (K) plays an important physiological role in carbohydrate and protein metabolism of plants, in the processes of photosynthesis and water exchange, increases resistance to wilting and premature dehydration, strengthens plant tissues and makes them more resistant to diseases and pests.
It easily moves from old plant tissues, where it has already been used, to young ones. The lack of potassium, as well as its excess, negatively affects the quantity and quality of the crop. With an excess of potassium, the flow of nitrogen into the plant is delayed, growth inhibition, deformation and chlorosis of leaves, primarily old ones, occurs. In later stages, mosaic spots appear, the leaves wither and fall off. Excess potassium also impairs the absorption of magnesium or calcium.
Magnesium (Mg) is a part of chlorophyll and is directly involved in photosynthesis. And it is also necessary for the formation of a reserve substance of phytin contained in plant seeds, and pectin substances.
Magnesium activates the activity of many enzymes involved in the formation and transformation of carbohydrates, proteins, organic acids, fats, affects the movement and conversion of phosphorus compounds, fruiting and seed quality. The maximum content of magnesium in the vegetative organs of plants is observed during the flowering period. After flowering, the amount of chlorophyll in the plant sharply decreases and magnesium flows out of the leaves and stems into the seeds, where phytin and magnesium phosphate are formed.
Lack of magnesium manifests itself in yellowing of leaves, chlorosis.
Calcium (Ca) participates in carbohydrate and protein metabolism of plants, the formation and growth of chloroplasts. It is necessary for the normal assimilation of ammonia nitrogen by the plant, and makes it difficult to restore nitrates to ammonia in plants. The construction of normal cell membranes is highly dependent on calcium.
Unlike nitrogen, phosphorus and potassium, which are usually found in young tissues, calcium is found in significant quantities in old tissues, while it is more in leaves and stems than in seeds.
Sulfur (S) is a part of the amino acids cystine and methionine, is an integral part of proteins and some vitamins, affects the formation of chlorophyll. Lack of sulfur leads to chlorosis, primarily of young leaves.
Other nutrients are no less important - iron, copper, manganese, molybdenum, zinc, cobalt, boron and others, which are usually called microelements. They are consumed by plants in small quantities, but their deficiency leads to serious defects in plant development. The content of trace elements in a plant is calculated in hundredths and thousandths of a percent.
- Iron (Fe) is part of the enzymes involved in the construction of chlorophyll, although this element is not directly included in it. Iron is involved in the redox processes in plants; it is an integral part of respiratory enzymes. Iron deficiency leads to the breakdown of growth substances (auxins) synthesized by plants, while the leaves become pale yellow. It is most often observed with an excess of carbonates and in heavily calcareous substrates. Iron cannot move from old tissues to young ones.
- Copper (Cu) is a part of copper-containing proteins, enzymes, it also takes part in the process of photosynthesis, carbohydrate and protein metabolism.
- Manganese (Mn) is a part of redox enzymes and takes part in photosynthesis, carbohydrate and nitrogen metabolism.
- Molybdenum (Mo) plays an important role in nitrogen nutrition. It is localized in young growing organs and less in stems and roots. With a lack of molybdenum, the development of nodules on the roots of leguminous plants and nitrogen fixation are delayed. The introduction of molybdenum into the soil promotes the absorption of nitrogen fertilizers by plants, but a high content of molybdenum is very toxic to plants.
- Zinc (Zn) influences the metabolism of energy and substances in the plant. With a lack of zinc, the content of sucrose and starch decreases, the accumulation of organic acids increases, the content of auxin decreases, protein synthesis is impaired, and growth retardation is characteristic.
- Cobalt (Co) participates in the biological fixation of molecular nitrogen.
- Bor (B) participates in the reactions of carbohydrate, protein, nucleic acid metabolism and other processes. Plants need it throughout their entire life span. First of all, young leaves and points of growth suffer from its deficiency. Excess boron burns the lower leaves, they turn yellow and fall off.
The deficiency of a certain nutrient will not slow down the effect on the development of the plant, but it is often very difficult to determine the true cause of the growth disorder. An excess of one element can inhibit the absorption of another, therefore, introducing an excess of one substance, we can cause starvation in another. It is important not only to add all the necessary nutrients, but also to choose the right ratio.
Lime fertilizers are divided into (Fig. 7.4): 1) hard limestone rocks that require grinding or burning 2) soft limestone rocks that do not require grinding 3) industrial waste, rich in lime.
By the content of CaO and MgO, solid rocks are divided into the following groups: limestones - 55-56% CaO and up to 0.9% MgO dolomitized limestones - 42-55% CaO and up to 9% MgO dolomites - 32-30% CaO and 18-20 % MgO. According to the content of clay, sand and other impurities, solid rocks are also divided into pure calcareous rocks - no more than 5% of impurities (limestone, dolomite) marly or sandy calcareous rocks - 5-25% marl or sandy calcareous rocks - from 25 to 50% clay or sand.
Soft calcareous rocks include calcareous tuffs - 80-98% CaCO3 drywall (lake lime) - 80-95% CaCO3, etc.
Of industrial waste, shale ash contains 30-50% CaO, 1.5 - ^, 0% MgO, as well as other defecate elements - 60-75% CaCO3, 10-15% organic matter, as well as N, P2O5, K20.
Limestones - 75-100% Ca and Mg in terms of CaCO3 (55-56% CaO, 9% MgO) Dolmitized limestones -
79-109% Ca and Mg in terms of CaCO3 (42-55% CaO and up to 9% MgO)
Dolomite flour -100% CaCO3 and MgCO3, <30-32% CaO and 18-20% MdO)
80-90% CaCO3, 0.1% P205 (up to 25% clay and sand admixture)
Burnt lime (CaO) - up to 170% CaCO3
Slaked lime (Ca (OH),) - up to 135% CaCO3
Defective dirt (defect) - up to 40% CaO
(60-75% CaCO3), 10-15% organic matter, N-0.5%, P205-1-2%.
Fig. 7.4. Classification of lime fertilizers
The main lime fertilizers are limestones - 75-100% of Ca and Me oxides in terms of CaCO3. Lime materials containing up to 25% sand and clay can be used. However, the action of this fertilizer is slow and, of course, good quality limestone should be used whenever possible. This is a prerequisite for high liming efficiency.
Dolomitized limestone with a content of 79-109% of the active substance (a.i.) in terms of CaCO3 can be recommended in crop rotations with legumes, potatoes, flax, root crops, as well as on highly podzolized soils.
Marl with CaCO3 content up to 25-75% and clay with sand up to 20 ^ 0% also acts slowly. It is advisable to use on light soils.
Chalk - 90-100% CaCO3, acts faster than limestone, valuable lime fertilizer in finely ground form.
Burnt lime (CaO) with a CaCO3 content of more than 170% is a strong and fast-acting lime material.
Slaked lime (Ca (OH) 2) with CaCO3 content up to 135% is a strong and fast-acting lime fertilizer.
Dolomite flour with a CaCO3 and] Y2CO3 content of about 100% acts more slowly than calcareous tuffs. It is important to use it where magnesium is needed.
Calcareous tuffs - 75-96% CaCO3, impurities up to 25% clay and sand, also up to 0.1% P2O5, act faster than limestone. They are found in low places in the Non-Chernozem zone.
Defective dirt (defecation) - waste of beet sugar factories. It consists mainly of CaCO3 and Ca (OH) 2. Lime content on CaO up to 40%. In addition, it contains 0.5% nitrogen, P2O5 - 1-2%. It is important not only on acidic soils, but also on chernozems in beet-growing areas.
In addition to the listed materials, the following industrial wastes are used in liming practice.
Shale ash from cyclones is a dry pulverized material with an active ingredient content of 60-70%.
Dust from kilns and cement plants with a CaCO3 content of over 60%. Usually used on farms adjacent to cement plants. These lime materials are applied by machines with closed containers and with pneumatic devices.
In addition, metallurgical slags are also used, mainly in the regions of the Urals and Siberia. They are usually non-hygroscopic and spray well.
The need for limestone materials is usually covered primarily by local resources - lime-containing industrial waste and local deposits of unconsolidated carbonate rocks. In most cases, these are calcareous tuffs, lake lime, loose chalk, dolomite flour, etc. However, in the country as a whole, local lime materials and lime-containing industrial wastes do not play a major role in the balance of lime materials.
The main lime fertilizer - limestone flour - is obtained by breaking hard rocks - limestones. It is a highly effective lime fertilizer suitable for all crops. Dolomite and magnesia limestone flour containing magnesium, first of all, must be used on soils of light granulometric composition. Cement dust contains a significant amount of potassium, has a very fine particle size distribution and is a fast-acting lime fertilizer. Its application is especially effective on soils poor in mobile compounds of potassium and under crops sensitive to the lack of this element.
The range of lime fertilizers can be significantly expanded through the use of loose deposits of local lime fertilizers: tuff, drywall, chalk, etc. Their use is advisable in the farms close to the deposits.
Sometimes lime fertilizers are used that do not meet the requirements of the standard and technical conditions, the uniformity of application is lower than the agrotechnical requirements. All this leads not only to a decrease in the efficiency of soil liming, but in some cases (with overlimening or uneven lime application) to negative consequences.
Organic fertilizers can also be additional sources that have a positive effect on the change in soil acidity (the calcium content in terms of CaCO3 is 0.32 -
- 40%) and phosphate rock (neutralizing capacity of about 22% CaCO3). In addition, calcium can enter the soil with atmospheric precipitation (about 15-25 kg / ha), but its role in influencing acidity is negligible and is not taken into account when recalculating the balance. The calcium contained in superphosphate also does not significantly affect the reaction of the soil.
When compiling a calcium balance, its removal by plants is also taken into account. The approximate removal of calcium and magnesium with the yield of agricultural crops is presented in table. 7.8.
Potassium preparations, undoubtedly have a positive effect on all plants. But, due to the fact that most of these products contain a chloride component, its use can harm some plants and soils. Fertilizing the soil with potassium chloride is recommended only in the fall and in a strictly limited amount, since chlorine is harmful to many garden crops. Long-term use of the drug negatively affects the condition of the soil - it can become acidic. In addition, potassium chloride contributes to the accumulation of salts in the soil.
Despite these disadvantages, fertilization with potassium chloride is indispensable on sandy, podzolic, peaty and sandy loam soils, where productivity is achieved only through the introduction of fertilizer mixtures.
There are also vegetables that, during the ripening process, absorb a lot of potassium substances, which leads to depletion of the soil. With a deficiency of potassium, plants become weak, their growth and development is impaired. You can determine the lack of potassium component in the soil by the appearance of the plants:
- leaves lose chlorophyll, become shriveled, reddish spots appear on them, the edges dry out and acquire a brown color
- stems weak, poorly developed, curved, pale colored
- the root system is weak, poorly developed, which is why the plant is poorly fixed in the soil - it can be easily pulled out
- fruits are small, take a long time and develop poorly
- plants get sick, greens are covered with various blooms.