Lakhasly

introduction:

Clay in the soil represents an essential element that affects its physical and chemical properties, and thus plays a vital role in supporting the growth of plants and providing them with a suitable environment. Clay is known as a very fine natural earthy material that becomes plastic when mixed with water. It is defined as the size of the particles resulting from the mechanical analysis of sedimentary rocks. According to geologists, the particle size is the particles less than 4 micrometers, and in the study of soil it is the particles with a diameter less than or equal to 2 micrometers [1]. What is the importance and origin of clay minerals in desert soil, and what are the areas of their formation in the desert?
I_The importance of clay in soil:
a-Definition of clays minerals:
The term "clay mineral" refers to foliar silicate minerals and minerals that impart plasticity to clay and that harden when dried or fired. Clay minerals are a silicate layer that usually forms as a result of chemical weathering. Other silicate minerals on the Earth's surface. They are found high in shale, and are the most common type. From sedimentary rocks in cold, dry, or temperate climates, clay minerals are fairly stable and form an important component of soil. Clay minerals act as "chemical sponges" that contain water and plant nutrients dissolved from other minerals. This results from the presence of unbalanced electrical charges on The surface of clay grains, where some surfaces are positively charged and thus attract negatively charged ions, while other surfaces are negatively charged attract positively charged ions. Clay minerals also have the ability to attract water molecules, and because this attraction is a surface phenomenon, it is called adsorption, which is different from absorption because Ions and water are not attracted to the depth of clay grains. Clay minerals resemble mica in chemical composition, except that they have very fine grains, and are usually under a microscope. Like mica, clay minerals are formed in the form of flakes with irregular edges and one side is smooth [2].

b_The importance of clay in soil:
1_ Water retention : The presence of clay in soil plays a crucial role in water retention. The unique structure of clay particles allows them to absorb and hold water, providing a reservoir for plants during dry periods.[3]
2_Providing food supplies :Clay minerals in soil serve as a rich source of essential nutrients for plant growth, including potassium, calcium, and magnesium. Their presence enhances soil fertility and supports healthy plant development. [4]
3_ Improving soil aeration : Clay minerals contribute to improved soil structure and functionality by preventing particle aggregation and facilitating better air and water flow. This enhances root growth and nutrient uptake by plants. [5]
4_ Preventing corrosion and erosion :presence of clay helps prevent soil erosion and land degradation by stabilizing soil particles, reducing soil erosion, and maintaining its natural composition.[6]

C_ The difference between sand, clay and silt:

Send[7]
Clay[8]
Silt[9]

Particle size
from 2.0 to 0.02 mm in diameter
ranging from 0.002 to 0.0002 mm
ranging from 0.02 to 0.002 mm

Water permeability
Sand is characterized by good drainage and low water-holding capacity, and low nutrient content.
Clay has poor drainage, high water holding capacity and high nutrient content.
Silt is characterized by moderate drainage and water-holding capacity, and moderate nutrient content.

II_ Clay formation process in the desert:
a_How clay is formed in desert soil:
Genesis of clay minerals:
Clay minerals are formed as the following reaction occurs:
Liquid water + silicate minerals + appropriate conditions

Where clay minerals are secondary minerals consisting of hydrated aluminum silicates, they are formed by transformations of existing minerals or primary minerals, or they are formed by synthesis from solutions of their chemical components. The type of these minerals depends on the quality of the primary minerals present to which chemical changes occur, as well as on the quantity of components that are recombined to give A secondary clay mineral. We summarize the methods of clay formation as follows. Inheritance from the rock. Rocks can be broadly divided into three categories: volcanic and metamorphic.
Sedimentary by conversion from other clay minerals
The new formation consists of ions transported by soil water
Factors that form clay minerals

(Sedimentaire) or (Détritique) Clay minerals vary depending on whether their origin is from pre-existing rocks.

sedimentary

Or (Hydrothermale)

Hot aqueous solutions

The factors affecting the formation of these minerals are temperature, pressure, ionic concentration of the elements, the pH of the solutions present, and the potential of oxidation and reduction.

Weathering is considered

(Alternation/weathering)

: One of the basic processes in the formation of clay minerals and is divided into physical weathering (temperature difference and freezing, crystal growth, and wind)
Chemical weathering (dissolution, hydration, oxidation, reflux and hydrolysis)* [10]
b_Are desert conditions suitable for the formation of clay minerals?
Clay minerals are abundant in arid and semi-arid regions, where they play a major role in soil formation, water retention, and nutrient cycling. The most common clay minerals in these regions are smectite, kaolinite, and illite. Smectite is formed by the weathering of volcanic rocks and glasses, kaolinite is formed by the weathering of feldspars and micas, and illite is formed by the alteration of micaceous clays.[11]
C_Explanation of the presence of clay in desert soil:
1_Erosion and weathering:
Water erosion: It leads to water erosion, even in semi-arid areas , to the formation of large quantities of clay sediments that are transported and deposited in desert sedimentary basins.[12]
Chemical weathering: Chemical weathering processes, such as hydrolysis and carbonation, create clay particles from rock minerals, contributing to the formation of clay layers in desert soils.[13]
2_Wind:
Sandstorms play an important role in transporting clay sediments over long distances, contributing to the formation of clay layers in desert soils.[14]
3_Human activity :
Agricultural practices, such as plowing and irrigation, contribute to the formation of clay particles from the soil, which can lead to the formation of clay layers in desert areas reclaimed for agriculture.[15]
4_Volcanic activity:
Volcanic eruptions can release large amounts of ash and gases containing clay particles, which may form layers of clay in desert soil when deposited on the ground.[16]
III_The location of clay in the desert:
a_The absence and presence of clay in desert soil and its impact on agriculture:
Improving the soil's ability to retain water:
Clay particles have a relatively large surface area, making them capable of absorbing large amounts of water. This property plays an important role in improving the soil's ability to retain water in dry environments.[17]
Improving soil structure:
Clay binds sand particles together, improving the soil structure and making it more stable. Clay also helps reduce soil erosion caused by wind and water.[18]
Increasing soil fertility:
Clay contains many essential nutrients for plants, such as nitrogen, phosphorus and potassium. Clay also helps exchange cations, making these nutrients more available to plants.[19]
Improving soil aeration:
Although clay may reduce soil porosity, it can improve soil aeration by creating fine paths that allow air to flow within the soil.[17]
Enhancing soil biological activity:
Clay provides a suitable environment for the growth of many beneficial soil microorganisms, such as bacteria and fungi. These organisms play an important role in improving soil fertility and converting organic matter into nutrients for plants.[18]
b_Reclamation of clay soil in the desert:
Improving drainage:
Drainage in clay soils can be improved by creating suitable drainage systems, such as channels or pipes, or adding materials such as sand or gravel to increase the pore space in the soil.[20]
2. Increase ventilation:
Aeration of clay soils can be increased by deep plowing, or adding materials such as straw or sawdust to increase the organic surface area of ​​the soil.”[21]
3. Treating acidity:.
The acidity of clay soil can be treated by adding lime or dolomite to raise the pH to the appropriate level for plant growth.[22]
4. Adding organic materials:
. Adding organic materials such as manure or animal manure is necessary to improve the structure and fertility of clay soil, and provide important nutrients to plants.[23]

C_Irrigation of clay soil:
Water permeability in clay soil:
Clay soils have very fine particles, creating very small pores between them. These small pores reduce the movement of water through the soil, resulting in low water permeability. In addition, clay soils tend to stick together, making it more difficult for water to penetrate For soil.[24]
Flood irrigation:
This is the most common method of irrigating clay soil, in which the soil surface is drenched with water until it becomes saturated. However, flood irrigation can lead to water wastage, weed growth, and soil erosion.[25]
Sprinkler irrigation:
Water is sprayed on the surface of the soil using sprinklers or hoses. This method is more water efficient than flood irrigation, but may not be suitable for heavy clay soils that absorb water slowly.[26]
Drip irrigation:
Water is delivered directly to the roots of plants using drip irrigation systems. This is the most water-efficient method of irrigating clay soil, but it may be more expensive than other irrigation methods.[24]
Soil moisture test:
Before irrigating the soil, it is important to test the soil moisture to confirm the need for irrigation. This can be done using a soil moisture meter or simply by placing your finger in the soil.[26]
Watering deeply:
When irrigating clay soil, it is important to irrigate it deeply to ensure that the water reaches the plant roots. This can be done by irrigating the soil for longer periods or by using drip irrigation systems.”[24]
Avoid over watering:
It is important to avoid over-irrigating clay soil, as this can lead to stagnant water draining and root damage[25].
d_Clay soil and salts:Salinity affects the properties of clay soil, including drainage, aeration, pH balance, and nutrient absorption. These changes can lead to decreased agricultural productivity and soil degradation."[27]