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Mineral riches are the inorganic chemical compounds present in the soils. Soil minerals are formed due to the weathering of rocks. Soil is generally composed of 45 – 60% minerals, 5-10% organic matter, 15 – 25% air, and 25 – 35% water. Soil with all the components in balanced proportions is called fertile soil. Soil mineral riches supply all the essential elements to plants.
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Key Takeaways: Mineral riches, soil, weathering, essential elements, types of minerals, soil-forming minerals, functions of soil mineral riches.
What are Soil Mineral Riches?
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Soil consists of different mineral elements like nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, iron, manganese, molybdenum carbon and their compounds. These mineral nutrients in the available forms are very important for the growth and development of plants. All these mineral elements, their free ions, and compounds form soil mineral riches.
Soil Minerals
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Formation of Soil Mineral Riches
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The topmost layer of the solid part of the earth is called the crust. The earth’s crust consists of rocks with chemical compounds in different proportions. Due to the influence of wind, water, and biological agents, these rocks are disintegrated into simpler compounds or elements.
Weathering of rocks
The process of disintegration of rocks is called weathering. A thin layer of loose, mineral matter on the surface of the earth’s crust is called soil. According to some scientists, it takes a few thousand years for the formation of an inch thick layer of soil. So, soil mineral riches are a by-product of a complex of mechanisms.
Fertile Soil
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Fertile soil is a mixture of mineral particles, organic matter, soil flora, soil fauna, water, and air. Soil flora includes plant roots, bacteria, algae, and fungi. Soil fauna includes earthworms, insects, nematodes, and rodents. Organic matter in the soil is a result of the death and decay of plants and animals.
Soil components
Both soil flora and fauna are responsible for the conversion of organic matter into brown and fine organic matter called humus. The relative size of mineral particles in the soil is called soil texture. Soil texture and quantity of organic matter are responsible for soil aeration. Soils get water through rains or the capillary action of the groundwater. Soil mineral riches are available to plants due to a combined action of all the above factors.
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Types of Minerals in Soil
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Soil mineral riches form about 40-45 per cent of the total volume of the soil. Soil mineral riches can be classified as primary minerals and secondary minerals based on their origin.
Primary Minerals
Soil mineral riches that have been in the existing form since their formation from parent rocks are called primary minerals. Primary minerals may undergo physical changes, but not chemical changes. Sand and silt consist of these kinds of minerals. Generally, these mineral particles are larger with irregular surfaces. Some of the primary minerals in soil mineral riches consist of crystalline minerals like siliceous minerals, silicates, apatite, ferrous minerals, titanomagnetite, volcanic gases and non-crystalline minerals.
Primary Minerals
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Secondary Minerals
These are the finer particles of the soil mineral riches. They are smaller than the primary minerals. There is a change in the chemical properties of these minerals since their formation from parent rocks or deposition from other places. Though they are smaller in size, their surface areas are proportionately larger.
Secondary Minerals types
Due to an increase in the surface area, these particles retain a lot of soil moisture. Fine silt and clay particles have this kind of soil mineral riches. Some of the important secondary minerals in the soil mineral riches are carbonates, halides, hydroxides, oxides, phosphates, phyllosilicates, and sulphates.
Soil Forming Minerals
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The chemical names of soil-forming mineral riches are as follows:
Calcite: It is a colourless or white mineral substance. It is a major component of sedimentary rocks that are formed from calcium carbonate.
Carbonates: Chemical combination reaction between magnesium hydroxide and calcium hydroxide with carbon dioxide forms carbonates.
Dolomite: It is calcium-magnesium carbonate. It is a chief source of magnesium in different soils.
Gibbsite: Chemically it is aluminium hydroxide. It is also called hydrargillite. It is an important aluminium ore in soils.
Goethite: It consists of iron oxide-hydroxide. It is a polymorph.
Gypsum: It is a soft calcium sulphate dehydrate mineral. It is found in sedimentary rocks and is water-soluble.
Soil forming minerals
Hematite: It is a hydrated iron mineral. It is red to blackish-red in tint and swells upon absorbing water.
Limonite: It is hydrated ferric oxide. It is yellow to brown.
Siderite: It is also a kind of iron mineral. It is generally found in water-logged soils.
Sulphate group: It is formed by the chemical combination of sulphur and oxygen ions. It reacts with calcium ions to form a calcium sulphate compound.
All these compounds provide essential mineral nutrients to plants.
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Functions of the Soil Mineral Riches
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- Soil mineral riches form the basic structural and chemical composition of the soil.
- The soil texture is due to the relative sizes of the soil particles. This property of soil mineral riches decides the water holding capacity and aeration of the soil.
- The relative arrangement of soil particles along with soil organic matter gives a proper structure to the soil. This property of soil mineral riches decides the feasibility of cultivation.
Soil minerals play a vital role in plant development
- Different ions in soil mineral riches are a source of nutrition for the growth and development of plants.
- The presence of essential elements in the soil is very important for the cultivation of different crops.
- The quality of groundwater is directly related to the number of chemical elements in soil mineral riches.
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Things to Remember
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- Inorganic chemical compounds in soils are called minerals.
- Soil mineral riches are formed due to the weathering of rocks. The disintegration of rocks into fine soil particles is called weathering.
- Soil minerals without any change in their properties are called primary minerals.
- Soil minerals with changes in their chemical properties are called secondary minerals.
- There are different soil-forming minerals like calcite, dolomite, gypsum, hematite, etc.
- Different ions in soil mineral riches are a source of nutrition for the growth and development of plants.
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Sample Questions
Ques: What are soil mineral riches? How are they essential for the growth and development of plants? (2 marks)
Ans: Different chemical elements in soils from soil mineral riches. They are nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, iron, manganese, molybdenum, etc and their compounds. All these mineral elements, their free ions, and compounds form soil mineral riches.
These mineral nutrients in the available forms are very important for the growth and development of plants. Vegetative growth, flower formation, and fruit formations depend on these essential elements. Without these elements, plants cannot complete their life cycles.
Ques: How are soil mineral riches formed? What are the factors that influence their formation? (2 marks)
Ans: The topmost layer of the earth crust is called soil. The earth’s crust consists of rocks with chemical compounds in different proportions. Due to the influence of wind, water, and biological agents, these rocks are disintegrated into simpler compounds or elements. The process of disintegration of rocks is called weathering.
Soil is formed due to physical, chemical and biological factors. Sunlight supplies heat to rocks. Rocks expand during the daytime and contract during night-time. So, rocks develop cracks. Water freezes in gaps to widen the gap in rock crevices. The roots of plants exert pressure in gaps. Carbon dioxide from roots forms carbonic acid after being combined with water. Carbonic acid and humic acid in organic matter further make soil particles finer.
Ques: What is meant by soil riches? What are the two kinds of soil minerals? (3 marks)
Ans: Essential elements in soil form soil mineral riches. Soil mineral riches are classified as primary minerals and secondary minerals based on their origin.
Soil mineral riches that have been in the existing form since their formation from parent rocks are called primary minerals. Some of the primary minerals in soil mineral riches consist of crystalline minerals like siliceous minerals, silicates, apatite, ferrous minerals, titanomagnetite, volcanic gases and non-crystalline minerals.
Soil mineral riches that have been in a chemically different form since their formation from parent rocks are called secondary minerals. Due to an increase in the surface area, these particles retain a lot of soil moisture. Fine silt and clay particles especially have this kind of soil mineral riches. Some of the important secondary minerals in the soil mineral riches are carbonates, halides, hydroxides, oxides, phosphates, phyllosilicates, and sulphates.
Ques: What are soil minerals? Write about any five soil-forming minerals? (5 marks)
Ans: Chemical constituents of soil are called soil minerals. They are different types like
- Calcite: It is a colourless or white mineral substance. It is a major component of sedimentary rocks that are formed from calcium carbonate.
- Dolomite: It is calcium-magnesium carbonate. It is a chief source of magnesium in different soils.
- Gibbsite: Chemically it is aluminium hydroxide. It is also called hydrargillite. It is an important aluminium ore in soils.
- Gypsum: It is a soft calcium sulphate dehydrate mineral. It is found in sedimentary rocks and is water-soluble.
- Hematite: It is a hydrated iron mineral. It is red to blackish-red in tint and swells upon absorbing water.
Ques: What are soil mineral riches? Write any five important functions. (5 marks)
Ans: Essential chemical elements in the soil form soil mineral riches. Their important functions are,
- Soil mineral riches form the basic structural and chemical composition of the soil.
- The soil texture is decided by the relative sizes of the soil particles and minerals in them.
- The structure of soil mineral riches decides the feasibility of cultivation.
- Different ions in soil mineral riches are a source of nutrition for the growth and development of plants.
- The presence of essential elements in the soil is very important for the cultivation of different crops.
Ques: Write a brief account of soil mineral riches. (2 marks)
Ans: Minerals present in soil are called mineral riches in the soil. Minerals that are required for the growth and development of plants are called essential elements. Soil minerals without any change in their properties are called primary minerals. Soil minerals with changes in their chemical properties are called secondary minerals. There are different soil-forming minerals like calcite, dolomite, gypsum, hematite, etc. Different ions in soil mineral riches are a source of nutrition for the growth and development of plants.
Ques: What is weathering? How is it useful in the formation of soil mineral riches? (2 marks)
Ans: The disintegration of parent rocks into soil particles is called weathering. Weathering of rocks occurs due to physical, chemical and biological factors. Mineral elements in rocks are in an unavailable form. Weathering makes these elements available in molecular, and ionic forms. These tiny compounds get mixed with soil solution. When plants absorb water, these mineral elements will also enter the plant body. Likewise, weathering helps plants absorb various essential elements in available forms.
Ques. How do the major factors of soil formation play an important role? (2 marks)
Ans. The major factors of soil formation are the nature of the parent rock and climatic factors.
- Parent Rock: Determines colour, texture, chemical properties minerals, content, permeability.
- Climate: Temperature, rainfall influence the rate of weathering and humus.
- Relief: Altitude and slope, determine the accumulation of soil.
- Flora, Fauna and Microorganism: Affect the rate of humus formation.
- Time: Determines thickness of soil profile.
Ques. What are some broad mitigation techniques of landslides? (2 marks)
Ans. Some broad mitigation techniques of landslide are as follows:
- Hazard mapping for locating landslides prone areas, so that building settlements can be avoided.
- Construction of a retention wall to stop the land from slipping.
- Increase in the vegetation cover to arrest landslides.
- The surface drainage control works to control the movement of landslides along with rainwater and spring flows.
Ques. List the six types of soil found in India. (2 marks)
Ans. Following are the six types of soil found in India:
- Red soil
- Black soil
- Alluvial soil
- Desert soil
- Mountain soil
- Laterite soil
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