Mineral Riches in the Soil

Soil minerals are naturally occurring, inorganic substances found in soil, such as sand, clay, and various metal oxides. Minerals in the soil are essential for plant growth and soil fertility. The outermost layer of the earth, known as crust, is covered with a mixture of organic and inorganic material called soil.

Soil serves as a medium for the growth of plants as it is rich in minerals and useful living organisms. The mineral composition of the soil is about 45-50%, organic matter constitutes about 1-5% of it whereas the remaining space is filled with air and water. Soil minerals examples include quartz, feldspar, mica, iron oxides, and calcium carbonate. In this article, we will cover minerals in the soil, their types, uses, and more.

Soil is the top layer of the Earth’s surface made up of tiny pieces of rock, minerals, organic matter like dead plants and animals, and water. It is where plants grow and where many animals live. Soil comes in different types each with its own characteristics that affect plant growth and the environment.

There are various types of soils based on their contents, texture, water holding capacity, aeration, etc. A few of these are as follows:

• Sandy soil: It consists of loose particles with poor nutrient content and very little water-holding capacity. 
• Clayey soil: Its particles remain very close together with little or no space. Aeration is poor but it has great water holding capacity.
• Loamy soil: It has moderate aeration and water-holding capacity. It is considered the best soil for agriculture due to its rich nutrient content and the above properties.
• Peaty soil: This type of soil is characterized by high organic content, making it dark and rich. It holds moisture well and is acidic, often found in marshy or wet areas.
• Chalky soil: Chalky soil is alkaline and contains a high concentration of calcium carbonate. It tends to be light and free-draining, with poor water retention.
• Silty soil: Silty soil has fine particles that are smaller than sand but larger than clay. It is fertile, retains moisture well, and has good drainage, making it suitable for a variety of crops.

The breakdown of various types of rocks over a period of time by natural elements leads to the formation of soil. Soil is formed by the following processes: weathering and paedogenesis. Hereunder, is a detailed explanation of minerals riches in soil.

Also Read: What is Soil Profile?

Mineral in the soil is one of the part of soil composition including humus, living organisms, water and air. Minerals are essential substance found in soil. It is the largest component of the soil, making up almost 40% to 45% of the total components. Soil is rich in minerals such as iron, phosphorus, calcium, magnesium, sulphur etc. Minerals constitute the major portion of soil. Minerals are necessary for plant growth and development. The minerals present in soil are absorbed by plants through their roots.

For example: Nitrate is an essential mineral in the soil as it helps in the synthesis of proteins. Magnesium is an important component of chlorophyll. The mineral soil is very supportive of plant growth. It also helps the soil highly rich in nutrients and make highly fertile which gives better crop result and increases economic development.

Minerals in soil are formed through various processes, primarily originating from the breakdown of rocks. Weathering of rocks is a key mechanism in minerals formation. During weathering, minerals within rocks are altered, creating new mineral compositions. Also, minerals can form through the deposition of dissolved substances from water sources, such as rivers or groundwater, which precipitate and accumulate over time. Biological activity, including the decomposition of organic matter by microorganisms also contributes to mineral formation by releasing ions and nutrients into the soil. Overall, the combination of these processes results in the continuous generation and transformation of minerals within the soil profile.

Soil minerals are of two types: Primary minerals and secondary minerals.

Primary Minerals of Soil

These minerals have not undergone any alteration since their deposition. They are similar to their parent material. Often these materials are bigger in size and irregular in shape. These primary minerals are usually found in sand and silt. Primary minerals get formed at elevated temperatures on account of cooling magma during the original solidification of rock or during metamorphism. They are usually derived from igneous and metamorphic rocks in soil.

In most soils feldspars, micas, and quartz are the main primary mineral constituents. Other examples of the primary minerals in soil include silica minerals and silicates, titanomagnetite, apatite, iron minerals, volcanic gases and non-crystalline inorganic constituents.

Secondary Minerals of Soil

They are formed as a result of weathering of the primary minerals. Secondary minerals are mainly found in fine silt or clay. The particle size of these minerals is much smaller due to the weathering process. These minerals have a large surface area that helps them retain moisture. Some examples of secondary minerals in the soil are hydroxides, phyllosilicates, oxides, carbonates, phosphates, sulfates and halides. Their addition to farmland is beneficial.

Common minerals present in the soil are as follows:

• Hematite: It is a common iron oxide compound with the formula Fe2O3 and is widely found in rocks and soils. It is red to blackish-red in color. On absorbing water it swells up to form hydrated iron oxide. Clay-sized hematite crystals occur as a secondary mineral formed by weathering processes in soil, and along with other iron oxides it is responsible for the red color of many tropical, highly weathered soils. 
• Limonite: Hydrated ferric oxide is called Limonite. It is yellow to brown in color. It is an important coloring and cementing agent in soil. Limonite is a residual soil produced by the decomposition of magnesium silicate (olivine) rocks in tropical environments. During weathering process most of the original rock is leached away leaving only its iron content, which is precipitated out in the form of iron sesqui-oxides to create a soft and highly porous soil.
• Goethite: Limonite when adsorbs water is called goethite. It is one of the most thermodynamically stable iron oxide. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient times for its use as a pigment.
• Gibbsite: It is the most common aluminum compound found in soil. It is found in highly weathered soil. It is a major mineral in soils of the tropics and subtropics where it may be the dominant mineral in the clay fraction. 
• Carbonate Group: Magnesium hydroxide and calcium hydroxide combine with carbon dioxide to form carbonates. Carbonates buffer soil pH and are an indication of the relative abundance of bases. The most common types are calcite (CaCO3) and dolomite [CaMg(CO3)2]. Less common soil carbonates include sodium carbonate (Na2CO3) and siderite (FeCO3). 
• Calcite: It is generally white or colorless. It is a major constituent of sedimentary rocks and consists of calcium carbonate. Calcite is present primarily in arid and semi-arid regions, where the source was either limestone parent rock or calcareous air-borne dust, although in some climates the soil calcite is the result of coral and shells. Calcareous soils typically have a pH above 7.5.
• Dolomite: It is the chief source of magnesium in the soil. Dolomite, a type of limestone which provides valuable nutrients to plants and helps change the pH of the soil by raising it to match the plants’ needs. It is also known as dolomitic lime/limestone. It provides more nutrients than straight lime.
• Siderite: It is an important mineral found in water-logged soil. It is produced by the alteration of other iron-bearing minerals. Its chemical formula is FeCO3. This iron carbonate mineral is commonly found in sediments and soils. It has been used as iron ore and for steel production.
• Sulphate group: It is formed by the combination of Sulphur and Oxygen ions. It further reacts with calcium ions to form calcium sulphate.
• Gypsum: It is found in sedimentary rocks and desert soils. It is water-soluble and leaches easily. It is chemically calcium sulfate. It plays a  beneficial role in breaking up compact soil, especially clay soil. It is useful in changing the soil structure of excessively heavy soils.

The soil minerals present in the soil have following uses:

• Quartz: Provides stability and drainage, ensuring proper aeration for plant roots.
• Feldspar: Helps with nutrient exchange and contributes to soil fertility, supporting healthy plant growth.
• Mica: Adds to soil structure, promoting water retention and preventing erosion.
• Iron Oxides: Give soil its color and help with nutrient availability to plants, aiding in photosynthesis and overall growth.
• Phosphorus: Absorbed in the form of phosphate ions. It is a constituent of cell membranes, certain proteins, all nucleic acids and nucleotides.
• Potassium: Required by meristematic tissues, buds, leaves and root tips. It maintains anion-cation balance in cells, is involved in protein synthesis, opening and closing of stomata, maintenance of turgidity of cells.
• Calcium: Plays an important role in synthesis of middle lamella, formation of mitotic spindles etc.
• Magnesium: Essential constituent of chlorophyll and helps in maintaining ribosome structure.
• Iron: Required in large amounts compared to other micronutrients. It is obtained as ferric ions from the soil.  It is an important constituent of transport proteins, it activates catalase enzyme and is essential for the formation of chlorophyll.
• Manganese activates many enzymes involved in photosynthesis, respiration and nitrogen metabolism. Its most important role is the splitting of water during photosynthesis.
• Molybdenum: Important constituent of enzymes of nitrogen metabolism like nitrogenase and nitrate reductase.
• Chlorine: Helps in determining solute constituent of cells and helps in maintaining its anion-cation balance. It plays important role in the water splitting reaction of photosynthesis.

In conclusion, soil minerals form a significant portion of soil composition. They include various elements like iron, phosphorus, calcium, magnesium, sulfur, and others, which are vital for plant nutrition and growth. These minerals are of two types: primary minerals, which remain unchanged since deposition, and secondary minerals, formed through weathering processes. Common soil minerals such as hematite, limonite, goethite, gibbsite, and others contribute to soil fertility, pH regulation, and overall plant health. Understanding soil minerals and their functions is essential for sustainable agriculture and environmental management.

Also Read:

• Mineral Requirements of Plants
• Soil Formation
• CBSE Class 11 Mineral Nutrition- Essential Mineral Elements
• Uptake and Transport Of Mineral Nutrients
• Soil Profile Diagram

Which Type of Soil is Rich in Minerals?

Loamy soil is typically rich in minerals due to its balanced composition of sand, silt, and clay, providing ample nutrients for plant growth.

What are Soil Minerals?

Soil minerals are naturally occurring, inorganic substances found in soil, such as quartz, feldspar, and various clay minerals, essential for plant growth and soil fertility.

Which Soil has the Most Minerals?

There isn’t one specific type of soil that has the most minerals, as mineral content can vary depending on factors like geographical location, parent material, and weathering processes.

How are Minerals Formed in Soil?

Minerals in soil are formed through processes like weathering, where rocks break down into smaller particles, and deposition, where dissolved substances precipitate and accumulate over time.

How do Organisms Contribute to the Formation of Soil?

Organisms, such as plants and microorganisms, contribute to soil formation through processes like organic matter decomposition, which releases nutrients and minerals into the soil, enriching its composition.