Mineral Riches in the Soil

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Soil Minerals

Soil minerals are the important substances found in soil which are basically produced as a result of the breakdown of large rocks. Examples of mineral riches in the soil are Potassium, Iron, Magnesium, Sulphur and Calcium. The mineral soil is very supportive for the plant growth.


The thin layer consisting of loose material that covers the Earth’s surface is called Soil. It is composed of both organic and inorganic materials, and its formation is a lengthy process that takes upto a thousand years. Soil is formed with the help of rocks when they break into small pieces and mix with organic matter. The process is known as weathering. Thus, soil is a mixture of various substances and particles, it is the mixture of rocks minerals and soil.


Besides minerals, soil consists of humus, living organisms, water and air. The organic substances formed after the decomposition of dead and decayed plants and animals is called humus. It makes the soil highly fertile. Many living organisms including microbes, worms, bacteria and fungi can be found in the soil that participate in generating the soil humus. Soil gets plenty of water through rain and underground water and also has aeration allowing living organisms to grow and function well inside the soil. Water and air in the soil are also very helpful for photosynthesis in the plants.


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Types of Minerals in Soil

The largest component in the soil are minerals and it makes upto 40-45 percent of the total components. The types of soil minerals are divided into two categories, which are as follows:

  1. Primary Minerals in the Soil: It is one of the types of minerals in soil and falls into that category of soil which have not been chemically transformed since the deposition. It is similar to their parent materials and is larger in size with irregular shape. These minerals are usually present in sand and silt. Examples of the primary minerals in soil include silica minerals and silicate, titanomagnetite, apatite, iron minerals, volcanic gases and non-crystalline inorganic constituents.

  2. Secondary Minerals in the Soil: It is the second category of minerals found in the soil and is formed after the weathering of primary soil minerals. It is mainly found in fine silt or clay minerals. The particle size of secondary minerals are much smaller as compared to the primary minerals since these are formed as a result of the weathering process. Having a large surface area, these minerals help in retaining moisture. Some examples of secondary minerals in the soil are hydroxides, phyllosilicates, oxides, carbonates, phosphates, sulfates and halides. These are beneficial to be added to the farmland.


Functions of the Soil Minerals

Soil plays an important role in various functions including food and other biomass production, biological habitat, gene pool, environmental interaction, physical and cultural heritage, and acts as a platform for man-made structures. The soil forming rocks and minerals are very helpful for the plant growth as it’s a great assistance to the plant life. A number of minerals are absorbed from the soil via the roots of the trees and plants. Most of the important minerals are magnesium and nitrate where the former helps in the production of chlorophyll allowing photosynthesis and the latter mineral is the major source of amino acids required to synthesise proteins. Absence of these essential minerals will lead to stunted plant growth.


Formation of Soil

Its formation involves breakdown of rocks in the rock cycle. Soil being a mixture of geological and organic materials, it is highly beneficial for the growth of plants. In contrast, sand is purely rocky material devoid of living organisms and therefore, sand is not great for the plant growth. Mixing manures, fertilizers or compost to the sand can turn into soil. Soil has therefore two parts, rocky materials and organic matter. Soil has a life cycle of its own. 


How are Rocks Broken to Form Soil?

  • Soil formation starts by disintegration of rocks under the influence of climate.

  • Sun, water and wind play important roles in weathering of the rocks.

  • Rain water dissolves rock elements; temperature fluctuations may cause differential weathering i.e. expansion and contraction of rock forming crystals.

  • Also, the freezing and thawing of water in rocks widen the cracks and the lichens, generally cyanobacteria or algae growing on the rocks release substances that help in powdering down the rocks.

  • In addition, mosses help in further breaking down the rocks.


Minerals Present in the Soil

Soil forming minerals are the major components of soil and mostly found are Sodium, Potassium and Nitrogen. Some of the other minerals of soil are as follows:

  • Hematite - It is red to blackish red in appearance and it swells up when it absorbs water forming hydrated iron oxide.

  • Limonite - It is yellow to brown in colour and it is hydrated ferric oxide and acts as a cementing and coloring agent for soil.

  • Goethite - Goethite is formed when limonite adsorbs water. 

  • Gibbsite - It is the most common Aluminium compound present in the soil. It is present in highly weathered soil.

  • Carbonate Group - Calcium hydroxide and Magnesium hydroxide combine with carbon dioxide to form carbonates.

  • Calcite - Calcite is white or colourless and the major constituent of sedimentary rocks, consisting of calcium carbonate.

  • Dolomite - It is the chief source of magnesium found in the soil.

  • Siderite - It is an important mineral present in the water-logged soil. It is generated by the alteration of other iron-bearing minerals.

  • Sulphate Group - It is formed by the combination of oxygen and sulphur ions. It further reacts to form calcium sulphate by reacting with calcium ions..

  • Gypsum - It is found in sedimentary rocks as well as desert soils. It is water soluble and it can be leached easily.

FAQ (Frequently Asked Questions)

1. What are the Minerals Found in Laterite Soil?

Ans. Laterite soil consists mainly of zircon, quartz, and oxides of titanium, tin, iron, aluminium and manganese, which remain during the course of weathering. Quartz is the most abundant mineral from the parent rock. The presence of laterites vary significantly according to their climate, location and depth.

2. What are the Minerals Found in Black Soil?

Ans. The minerals found in the black soil includes Iron, Aluminium and Magnesium. Black soil is deficient in Nitrogen, Phosphorus, Potassium and Humus. Black soil appears red in colour mainly due to its iron oxide content.

3. What are the Minerals Found in Forest Soil?

Ans. The minerals found in forest soil are organic, very acidic and have limited chemical fertility. Its texture may range from fine loams, to coarse gravels to silts, with sandy loams and sands.