Red Soil – Properties, Composition, Types & Advantages

What Is Red Soil?

Red soil develops in warm, temperate, and humid climates, comprising approximately 13% of Earth’s soils. It originates from the weathering of ancient crystalline and metamorphic rock, which results in a red color due to its high iron content.

These soils consist of thin organic and organic-mineral layers atop a red layer of alluvium. They contain significant clay content and are typically low in nutrients and humus. Their water holding capacity is often limited, posing cultivation challenges.

Suitable farming techniques like liming can enhance the fertility of red soils. Understanding the properties of red soil is crucial for successful agriculture in countries such as China, India, and Greece, where it is abundant.

Properties Of Red Soil

1. Red soils encompass various soil types such as ultisols, alfisols, and oxisols, characterized by their distinctive reddish color resulting from high iron content.
2. The reddish color of red soils can range from reddish brown to reddish yellow.
3. Red soils generally exhibit characteristics favorable for plant growth and agriculture.
4. They tend to be acidic in nature, which can have positive effects on certain crops but may also lead to nutrient deficiencies.
5. Red soils are prone to frequent drought, especially in drier regions.
6. These soils are commonly found in tropical and subtropical areas.
7. They possess a sandy texture, promoting good drainage.
8. Red soils often lack sufficient organic matter and fertility.
9. High levels of iron, aluminum, potassium, and magnesium are commonly present in red soils.
10. Proper soil management practices, including adding organic matter and fertilizers, can enhance the fertility and productivity of red soils

Composition Of Red Soil

Red soil consists of various components as discussed below:

1. Iron Oxides:

Red soil gets its distinct color from a high concentration of iron oxide minerals, such as hematite and goethite. These minerals give the soil a reddish or reddish-brown appearance.

2. Aluminum Oxides:

Red soil also contains aluminum oxide minerals, which contribute to its color and play a role in its properties. These minerals include gibbsite and boehmite.

3. Silica:

Silica, in the form of quartz, is another significant component of red soil. It contributes to the soil’s texture and helps retain moisture.

4. Organic Matter:

Red soil contains varying amounts of organic matter derived from decomposed plant and animal residues. Organic matter improves soil fertility, water-holding capacity, and nutrient content.

5. Clay and Silt:

Red soil generally has a high proportion of fine particles, including clay and silt. These particles contribute to the soil’s ability to retain water and nutrients.

6. Weathered Rock Fragments:

Red soil may also contain fragments of weathered rocks and minerals, such as granite, basalt, and quartzite. These fragments contribute to the soil’s mineral content and texture.

Types Of Red Soil

1. Red Clay Soil:

Red clay soil, also known as Ultisols, belongs to the category of mineral soils without any calcareous material. It is characterized by a top layer with less than 10% weatherable minerals and a saturation base below 35% throughout the soil profile. Ultisols are typically found in tropical regions with humid temperatures, such as Africa, Asia, and South America.

2. Red Loam Soil:

Red loam soil is formed through the decomposition of granite, gneiss charnockite, and diorite rocks. It is cloddy, porous, and deficient in concretionary materials. This soil type lacks nitrogen, phosphorus, and organic matter but contains a sufficient amount of potash. However, red sandy loam soil is not highly fertile, making it less suitable for agriculture. It is predominantly found in states like Andhra Pradesh, Telangana, Karnataka, Eastern Tamil Nadu, Orissa, Jharkhand, and Madhya Pradesh.

3. Red Laterite Soil:

Red laterite soil, known as “brick soil,” is rich in iron and aluminium. It develops through intensive and prolonged weathering of the underlying parent rock. The high iron oxide content gives the soil its characteristic red color. Red laterite soils are commonly found in hot and wet tropical regions situated between the tropics of Cancer and Capricorn. They also serve as a source of aluminium ores.

4. Red Yellow Soil:

Red yellow soil is associated with broad-leaved forests typically found in humid subtropical regions. These soils have an acidic reaction and contain lower levels of humus compared to other soil types. The red-yellow color is attributed to the presence of ferric hydroxide. The thickness of these soils can vary from 30 to 70 cm, and their distribution includes regions like China, the Southern United States, southeastern Australia, and New Zealand.

5. Red Sandy Soil:

Red sandy soil is characterized by its light, warm, and dry nature. It contains a high proportion of sand and is low in nutrients, making it unsuitable for cultivation. The soil’s poor fertility, lack of organic matter, and inadequate nutrient content limit its agricultural potential. Red sandy soil is typically found in regions with arid, semi-arid, and humid rainfall patterns.

6. Red Gravel Soil:

Red gravel soil contains a significant percentage (usually 20% or more) of gravel in the top layer, which is distributed throughout the soil profile. The presence of gravel impedes plant growth, as it acts as a barrier and hinders the development of roots. These soils lack essential nutrients and can cause damage to plants due to root penetration by the gravel particles. As a result, agriculture is not advisable on red gravel soils. However, the presence of gravel helps to improve the structure of clay soils by creating air pockets that store oxygen. Plants such as perennials, ornamental grasses, and herbs can thrive in this type of soil.

Suitable Crops For Red Soil

Category	Crops
Fruits	Bananas, Oranges, Pineapples, Avocados
Sugarcane	Sugarcane
Vegetables	Carrots, Potatoes, Celery, Beets, Spinach, Beans, Peas, Corn

Red Soil Test Methods

Various types of tests are conducted to assess the properties of red soil. These tests include:

1. Sieve Analysis:

Arrange sieves in the order of 4.75mm to 2.56mm, 1.18mm, 600micron, 300micron, 150micron, 75micron, and pan.

Take 1kg of fine soil and place it on the top sieve.

Perform manual sieving 15 times and record the weight retained on each sieve.

Plot a gradient curve using the obtained values and draw a semi-log graph sheet to determine the grade of red soil.

2. Comprehensive Strength Test:

Use a standard mold size of 150*150*150 for casting.

Cure the concrete cubes for 14 days and determine the comprehensive strength using a compression testing machine (CTM).

3. Flexural Strength Test:

Use a standard mold size of 500*100*100 for casting.

Cure the specimens for 28 days and conduct the flexural strength test using a universal testing machine (UTM).

4. Water Permeability Test:

Use a standard mold size of 100*100 for casting.

Cure the concrete cylinders and conduct the water permeability test using a concrete permeability apparatus.

Perform the test for 14 days for ordinary mix and samples with partial replacement.

Test each specimen for 100 hours.

5. Porosity Test:

Use a standard mold size of 100*100 for casting.

Cure the concrete cylinders.

Conduct the porosity test by immersing the specimens in a water tank for 24 hours and then drying them in a hot air oven for 24 hours.

Perform the test for 14 days for ordinary mix and samples with partial replacement.

Advantages Of Red Soil

1. Red soil has a higher water-holding capacity compared to other types of soil.
2. It is suitable for cultivating crops such as rice, sugarcane, wheat, and pulses.
3. Red soil is well-suited for dry farming techniques.
4. It is highly effective when used in concrete.
5. Red soil can reduce the need for cement and replacement materials in concrete.
6. It exhibits good resistance to fluid passage, making it impervious.

Disadvantages Of Red Soil

• Red soil is characterized by its thinness, poor quality, porosity, and loose gravel.
• It is deficient in lime, phosphate, and nitrogen.
• Red soil has a low water holding capacity.

Faqs