Physical-chemical absorbability
Depending on condition, if compounds inside of the solution are dissociated, at that case separate ions may be absorbed by soil. If only cations are absorbed in the result of chemical reaction, and if this reaction goes under definite physical strength, such absorption is called physical and chemical absorbability of soil. Reaction that given below is able to elucidate this:
[Soil] Ca + 2Nas Cl = [soil] Na + Cas Cl2
Physical chemical absorbability has one feature; cations of soil replace each other in result of change reaction. Cations absorbed in such way are called as “change” or ”absorbed” cations. It is necessary to note especially that all mass of the soil does not take part in the process of absorption. Creator of absorption process in soil is fine particles of colloid.
Such colloid particles are called "absorbability" the soil. Most specific feature of this complex is an ability to replace cation in self with cation solution. By composition absorbing complex consist of very different chemical compounds. It includes both mineral and organic colloids. That is why its called as complex. In various soil types amount of absorbing complex is different. So, but he absorbing complex is high in some soils and low in some. In soils rich with fine particle, clayey and organic matters absorbing complex is high and in soils with less sandy the absorbing complex is low.
Chemical absorbability:
Besides aforementioned various absorption methods food matters could be saturated by chemical absorbability of soil and protected. Different compounds in structure of the solution or solutions contact with soil and salts in them get into reaction with each other and form new compounds. This absorbability of the soil as passes on definite chemical reaction it is called as chemical absorbability. One of essential features of the absorbability is creating of sometimes less solved and sometimes non-soluble compounds in the result of reaction.
As we know there are different salts in structure of the soil solution. e.g: Salt of "Na3 CO4" gets into some chemical reaction with "Ca Cl" salt and at result creates calcium phosphate salt which is hard soluble:
3Ca2 Cl + 2Na3s PO4 =
=Ca3 (PO4) + 6Nas Cl
Hardly soluble salt of "Ca3 (PO4)2 in result of this reaction has settled from structure of the solution completely and may be absorbed by soil. All soluble salts cannot be absorbed by soil in the result of process of chemical absorbability but in result of this reaction salts giving hard compounds are absorbed by soil by chemical method.
Energy of absorbing: Different cations have different energy of absorbing. But some cations are absorbed by soil quickly and some lately. As a whole energy of absorbing of cations depends on their valency. Univalent cation: Na, K, NH4. Some weak bivalent cations: Ca, Mg are absorbed by soil comparatively intensively. Among these cations despite univalency of "H" ion its absorbing energy is higher than al aforementioned cations. Therefore, hydrogen ion takes one special place among absorbed cations. Briefly absorbing complex of soil is always absorbed by cations. Depending on condition of land formation, composition of absorption complex is very different, too. In some cases absorption complex is saturated by hydrogen, sometimes by calcium and natrium cation. Depending on absorbed cations soils are divided in two parts: “saturated by bases” and non-saturated by bases". Ca, Mg, Na has settled in the absorption complex of the soil saturated by bases. But hydrogen ion has settled in the absorption complex of soil non-saturated by bases. Therefore as reaction of first is neutral and weak alkali but reaction of the second is sour. Black, chestnut, grey, brownish, saline soils can be noted as saturated by bases. But soils unsaturated by bases are podzol and swampy soils. Moreover, absorbed cations in the type of each soil are very different. Ca, Mg in absorption complex of black soils and Na in absorption complex of saline soils are taken as main one. Finally hydrogen ion is located in absorption complex of soils. Depending on structure of absorbed cations, soils have very different physical-chemical composition and structure. e.g: as Ca, Mg strongly maturates colloid particles of soil these soils have very clear and durable structure. If structure of the soil is clearer the physical feature of soil, i.e. aeration and water permeability is rather higher. Therefore, black soils can preserve high productivity. As we mentioned in absorption complex of saline soils Na cation was passed. As this cation is univalent, and maturation on colloids passes slow the structure of the soil formed is not so durable to water and at result of irrigation a soil loses its structure.
By spoiling structure of such soils their physical property gets spoiled and it may lose productivity gradually. At last, because hydrogen ion is in the absorption complex in podzol type soils, sometimes high acidity is formed in soil solutions. This creates suitable conditions for humus’s washing off in soil, too. As amount of rotten matters and especially of humus in such soil gets diminished gradually, so their productivity may be diminished, too.
Biological absorbability.
Biological absorbability has big role in absorption of food matters and its preservation in soil. They are small organisms in structure of soil that creates biological absorbability. Many food matters are absorbed in soil in result of activity of these organisms and so they protect these matters from washing off from soil.
Importance of the plants is big in biological absorbability, too. Plant’s roots passing to deep layer of the soil, take out food matters on top layer and gather then in soil as plant remainders. Biological absorbability has one special place in forming of nitrates in soil and its absorption. Nitrates in the soil may be absorbed only by biological absorbability. In general, biological factor can play close part not only in absorbability but even in generation of food matter and preserving of soil productivity on same level.
Mechanical composition of the soil.
Under influence of erosion process rocks turn to land and are met with deep chemical and mechanical changes. In eroded rocks we can clearly see mechanical particles of various size and diameter. Depending on pertografic and chemical structure of the rock, big rocks with few centimeters of diameter and then sand and clay particles are spread in eroded rocks. Plant roots and insects livings in soil play a big role in forming of the mechanical elements of the soil. Plant roots and insects gradually split big rocks and turn them in the form of fine particles. Different mechanical particles in soil are called as mechanical structure of that soil. Such mechanical particles form structure of the soil in the normal soils by being attached to each other.
If we sample of soil stirred up in the water, we’ll see settling of particles gradually to bottom of the water depending on the diameter. These mechanical particles in soil are very different both for their shape and for diameter of particles. Soil is divided in 2 parts for mechanical composition:
1. Skeleton of the soil - > 1mm
2. Fine part - < 1mm/
Skeleton of soil include particles more than 1 mm and fine part includes particles less than 1 mm. It is necessary to note especially that basic property of the soil has gathered in its fine part. Moreover sand, gas and silt particles in fine part of soil are differed by separate mechanical fractions. Learning of the mechanical composition of the soil has close link with practical problems. It is possible to say in a word that physical property of the soil or to be truer its link with irrigation, weather and hot depends on mechanical composition of soil. Finally structure of the soil, its chemical composition, absorbability and productivity is closely connected directly with mechanical composition. In most cases agricultural tools used in sowing of soils is connected with mechanical composition of that soil. Therefore, heavy clayey soil, light soil, sandy soils were distinguished among people since old times. To define mechanical composition of soils very different methods have been offered. As a whole method specifying the mechanical composition of the soil is called as mechanical analysis of the soil.
Methods offered are:
1. Method is method offered by professor Sabanin. According to this method mechanical composition of the soil is specified in the special apparatus. Principle of the Sabanin method is dependent on the volume and measure of the particles. According to this method fine part of the soil is separated into 4 mechanical fractions:
I fraction 25 mm - Sand
II fraction 0. 2-0s 05 mm- sandy dust
III fraction 0. 05-0,01 mm - dust
IV fraction < 0. 01mm - silt
Depending on percentage of the fractions noted above soil is divided into: clay, clayey, sandy, sand separate mechanical types. It is necessary to note especially that settling ability of mechanical particles inside of the solution: dependent on its special weight, shape and height. Method of Sabanin is called as analysis method in the silent water, too. Besides Sabanin’s method the method of professor Shenin is also applied in mechanical analysis.
Basic principle of this method is defining mechanical composition in flowing water. These scientists had special apparatus and mechanical composition of soil in the apparatus depends on the speed of the water, and it is separated into some mechanical fractions.
At last, the 3rd method is Fadeyev-Williams method. These scientists had taken Sabanin’s method as basic principle in their methods, too. Sabanin in general, had separated mechanical composition into some separate groups we noted below.
Diameter with mm
Stone >10 mm more
Small stone 10-3 m
Big 1 – 05 m
Sand middle 0.5- 0.25
Fine 0.25 - 0.01
Middle 02.01-0.005
Fine 0.005- 0.001
Silt < 0.001
Silt fraction is important mechanical fraction of soil. Because this fraction has gathered the most active parts of soil: colloids
In these fractions:
Mineral crumbs called as quartz, field spar, augite, garnet, limonite, tiff and dolomite had been spread.
Morphology of soil
Each soil mass during development appropriates special foreign morphological signs under influence of the different physical, chemical, biological processes. Soils have different morphological signs connected with changing of the condition.
Morphological sign of the soil depends on conditions land forming process. It is possible to say that morphological sign of the soil reflects its inside chemical property and productivity. Morphological method of the soil is one of basic methods in the field of research at present. Russian soils scientists have been first to develop the morphological method of the soil. Academician Ruprekht, professor Dokuchayev, Sibirtsev had improved morphological methods in their soil researches.
Foreign features of soils that characterized by simple vision are called as “morphological signs” of that soil. “Morphological signs” of soil shows its inner property. E.g: darker color of soil shows richness of organic matters in that soil, being in yellowish color shows presence of iron compounds in it and being in whitish color shows that there is much calcium – carbonate salts in soil. Moreover, according to morphological sign of the soil, we shall be able to specify generation of the same soil and concerning to what kind. From this reason soil morphology has both theoretic and practical importance. By folk habits people can define productivity of soil for its color. E.g: black land has more productivity than grey, brownish soils and it’s a well known fact. Basic morphological signs of the soil consist of:
1. Color of the soil
2. Structure of the soil
3. Compactness of the soil
4. Thickness of the soil layers
5. New formations of soil and its structure
6. Skeleton of the soil
7. System of the soil
1. Color of the soil: Color of the soil is considered as one of clearly visible morphological signs. In ancient times people used to name of soils for their color: black, yellowy, grey, and brownish and so on. Soils are very different according to color. When one defines color of the soil, it is difficult to name simply it in one color. Therefore when the color of the land is specified it is necessary to show tone and assortment of color in the first place. It is necessary to give degree of the color, too. E.g: black, strong black, blackish, grey, light grey, strong grey, greyish and so on. Color of the soil is dependent on its chemical structure and physical state. Chemical compounds inside of the soil giving color to soil are in the first place. e.g: iron compound gives yellow and reddish color to soil, organic compounds give black color to soil, SiO2 and Ca CO2 gives a soil whitish and these there mentioned colors when mixed with each other on various forms they create soils of different color. As we note above the color of the soil has great importance on agriculture. Due to color of soil we can identify its economic worthiness. As organic matter is high in black soil they are deemed to be most worthy soils. But grey and light colored soils have no so high economic value.
2. Structure of the soil: Separation of some soil mass to various parts under influence of definite physical strength in the different shape is called as structure for of soil and separated parts are called as soil structure.
That structure of the soil depends on organic and colloid minerals and lime salts in soil. Therefore we do not meet structure of the soil in some sandy soils. Basing on it soils are divided in general into two parts called structured and unstructured. By shape structure of soil is granular, nut type, cloudy. It is necessary to note especially that each type of soil has owns structure. e.g: granular forests are met in black, nut type in grey, chestnut soils, thin layer structure in saline soils. Soil structure has direct influence on its physical property. Suitableness of soils structure in permeability of water, being hot is one of primary conditions. Therefore, granular structure is considered in the agriculture as one of most valuable structures.
3. Compactness of the soil: Less or more porosity in oil form some definite compactness in the land. From this view soils are divided into solid, very solid, soft and loose compactness. In some cases there is no compactness in soil. Generally, as compactness degree in soil increases as get down from upper layers to lower layers. From one side low level of organic matters in layers and accumulation of much salt is dependant. Salts in the bottom layers give especially very high compactness. This is considered as one of basic morphological signs of the saline soils, too.
Thickness of the soil and layers of soil.
Depending on natural condition and land formation process thickness of soil is different. The thickness from top layer to mother rock is called thickness of soil layer. In many cases thickness of soil is 40-150 sm. In some cases in typical black soils the thickness of soil layer reaches 2,5 meter. Depending on geographical situation thickness of soil sometimes is high or lower.
General thickness of the soil is not more than 30-40 cms in high mountain regions. Its may be explained from one hand weak passage of land forming in mountainous regions and from other side washing-off of generated soils by floods. In foothill areas thickness of land layer reaches till 90-100 cms. But thickness of the plain land can reach at last till 150-200 cms in the regions. Big thickness of land layer in such regions is explained by settling of washed sediments from foothills to plains and gradual increase of land layer’s thickness. Economic value of the soil is specified with thickness of the some layers. E.g. humus layer is thick in black soils and it shows richness of organic matters in those lands. If humus layer sometimes has weak thickness, losing of organic matters gradually in those lands under influence of washing off is registered in the same land:
New formation of soil and its structural parts.
Compounds formed under influence of land formation in land vacuums are called new formations of that soil. Main importance in studying new formation of soil is to define chemical composition in that soil. New formations of soil consist of settled compounds of land solution basing on change of certain conditions. Generally, formations are divided in two groups, chemical and biological. From new chemical formations CaCO3, CaSO4 H2 O (gypsum), iron compounds and SiO2 can be shown in this regard. New formations of Ca Ca3 are mostly spread in 50-60 cms depth of soil. Such formations are called as white peep-holes. White peep-holes are considered from characteristic morphological signs for chestnut type soils.
Gypsum is found in saline soils as new formations. These formations are spread in the form of small crystals and sometimes in the form of big druse in deep layers of saline soils. In swampy soils iron oxides are spread from new formations. Such formations form one layer of grass color with greenish patterns in definite depth of soil, which is called grey layer. But in some cases, especially in podzol soils compounds of iron oxides form nets in land layer and they are called as ortschtein formations.
Typical podzol soils amount of ortshtein formations is so high hat even it forms ortstein layer. At last, formations of SiO2 forms sometimes crystallinity, and sometimes it is found in whitish podzol soils in amorphous shape. Such formations creates separate layer in podzol soils and it is called as pozdol layer.
Remainders of the plant roots and insects can be noted among from new formations. In some soils crumb rock pieces can be found inside of land layer of some lands. And sometimes big tree and plant remainders are not found and such remainders are deemed to be compounds generated from land formation process. Therefore such remainders are called as structural. Reason that soil is reddish in subtropical zones is erosion of Fe2 O3 (hematite) under influence of high temperature and plenty rainfall. This erosion passes so quickly that it separates an iron from mother rocks and passes to soil and changes its color and composition.
