Agricultural Science

Soil explained with its composition

len Alfred Ajibola - 03rd August, 2023 @ 06:34 PM

Topics in Agricultural Science

Clay soil explained with its types and characteristics Loamy soil explained with its characteristics Sandy soil: Characteristics of sandy soil and ways to make it fertile Soil explained with its composition Types of agricultural practices Crop rotation explained Benefits of crop rotation Differences between subsistence and commercial farming Subsistence farming explained with its characteristics What is commercial farming? Types of commercial farming Characteristics of commercial farming Importance of forest: Forest reserves in Nigeria Wildlife reserves in Nigeria and its importance Prevention and Control of Crop Pests Economic Importance of Crop Pests Classification of Insect Pests and their Economic Importance Agricultural machines and their uses Causes of soil erosion Ways to prevent soil erosion Asexual Propagation in Plants, Types and Examples

Academic Questions in Agricultural Science

Please click here to see all Questions and Answers

The ideal pH for the optimum growth of most agricultural crop is between _____.

  • A. 1 – 3.5

  • B. 4 – 5.5

  • C. 6 – 7.5

  • D. 8 – 9.5

  • E. 10 – 11.5

  • F. 12 – 13.5

People who go about their lives by raising and herding livestock such as cattle, sheep and goats are said to practice _____.

  • A. Pastoralism

  • B. Pasturalism

  • C. Herding

  • D. Herdsmen

  • E. Animalism

  • F. Anime Farming

The act of giving birth in pigs is called _____.

  • A. Calving

  • B. Piggery

  • C. Kidding

  • D. Farrowing

  • E. Calfing

  • F. Pigging

Which of the following is not a vegetable?

  • A. Cashew

  • B. Cocumber

  • C. Tomatoes

  • D. Carrot

  • E. Squash

  • F. Eggplant

All plants are crops.

  • A. True

  • B. False

In agriculture, macronutrients are essential nutrients required by plants. Which of the following is not a macronutrient?

  • A. Zinc

  • B. Sulphur

  • C. Calcium

  • D. Phosphorus

  • E. Potassium

  • F. Magnesium

Which of the following is false concerning micronutrients?

  • A. They are non-essential nutrients

  • B. They are required by plants in minute quantities

  • C. Iron is a micronutrient

  • D. Chlorine is a micronutrient

  • E. Copper is a micronutrient

  • F. Boron is a micronutrient

_____ is a term that describes the biological, chemical and cultural control tactics employed to make pest management economical, environmentally friendly and socially acceptable.

  • A. Integrated Pest Management

  • B. Integral Pest Management

  • C. International Pest Management

  • D. Inclusive Pest Management

  • E. Imbibed Pest Management

  • F. Inclusion Pest Management

What is Soil?

Soil is defined as the uppermost and biologically active layer of the earth's surface formed by weathering, and comprises of sand, silt, clay, minerals, water, air, organic matter, and living organisms. 

Depending on the soil's composition, it can serve various purposes such as building and construction, as a home to various organisms, for the storage of water, planting of crops, pottery, and so on. As an instance, sandy soil is utilized in building when mixed with cement, while loamy soil is suitable for planting various crops due to its high humus content.

You can read on soil erosion here.


From the above paragraph, we can deduce that the soil serves a variety of functions. They include the following:

  • The soil acts as a support and foundational medium. For instance, it is crucial for the growth of plants in agriculture.

  • It acts as a reservoir for water, thus making it an important part of water cycle. 

  • The soil is home to a variety of organisms.

  • It acts as a modifier of earth's atmosphere from the various activities carried out on it.

  • Please read on functions of the atmosphere here.


The life supporting functions of the soil is seen in various biochemical (life) cycles such as water cycle, carbon cycle, nitrogen cycle, ammonification, biogeochemical cycle and so on. It is considered a crucial part of the ecosystem since it contains the biotic (living) and abiotic (nonliving) components. In short, without the soil, the chances of life will be significantly decreased on earth.

Please read more on the components of the ecosystem here.


Alongside the atmosphere (air) and hydrosphere (water), the soil acts as a substrate on which various living organisms thrive. It is formed from the disintegration, or breaking down of rock via a weathering process resulting from climatic, biological and geographic factors.


Pedosphere is a term that refers to the entire soil present on the earth's surface. It interfaces with the lithosphere, atmosphere, hydrosphere and biosphere respectively.

You can read on agricultural terms and meanings here.



Composition of the Soil

Recall that we have various types of soil, and these have got their respective compositions. The types of soil in this instance refers to sandy, loamy and clay soil. However, understand that a typical soil is composed of about 50% solid, and 50% pores.

You can attempt Len Academy agricultural science questions for JSS1 here.


With regards to the solid components of the soil, it comprises of inorganic matter (minerals) and organic matter, in a ratio of 45 to 1. In addition, water and air are present within the soil's pore spaces at about 25% respectively. This is shown in the image below:

Components of the soil - Len Academy


Meanwhile, understand that the presence of negligible pores within a soil will lead to compaction, and this is a typical problem associated with clay soil.

You can read on the problems of agriculture in Nigeria here.


Note: The above paragraph explains only the composition of a general soil. Once again, it is important to stress that the composition of a specific soil, let's say sandy soil, will be significantly different from that of loamy and clay soil; and vice versa. 


  • With regards to the composition of sandy soil, it comprises of about 85% sand, 10% silt and 5% clay. This is shown in the image below:

Composition of Sandy Soil - Len Academy

Sandy soil consists of large soil particles that are quite widely separated, thus having good amounts of air spaces between them. For this reason, they barely stick together, and can be coarsed, gritty or grained in appearance.

Please read on sandy soil here.


  • Clay soil is composed of about 50% clay, 25% sand and 25% silt.

Composition of Clay Soil - Len Academy

Clay soil consists of fine (or powdery) particles that can become sticky when wet. This is so because the particles have very negligible spaces between them. As a result, they possess a good water retention capacity, and can easily become waterlogged.

Please read more on clay soil with its types and characteristics here.


  • Loamy soil comprises of about 50% silt, 25% clay and 25% sand.

Loamy soil appears to be dark and moist in appearance, with moderate-sized pore spaces. It is well-aerated, and has a decent water retention capacity. Also, loamy soil contains an abundance of humus (organic matter), thus making it the best soil for planting most crops.

Please read the details on loamy soil here.

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Amazing facts in Agricultural Science

Cows technically have one stomach, not four. However, a cow's stomach has four compartments. These are: rumen, reticulum, omasum and abomasum

Peanuts are legumes and not nuts

Although plants neither see nor hear, they can recognize their siblings and even give them preferential treatments

Squirrels do plant more trees (through their actions) than an average human in their lifetime. They often hide their acorns and nuts underground and forget about them

Cows have got the ability to walk up stairs, but not down stairs

A group of cows is called a team, drove or herd.

People just prefer to call them herd

Notable points in Agricultural Science

Below are characteristics of gymnosperms:

  1. Their seeds have cones that protect them.

  2. Sepals and petals aren't present in their cones.

  3. Stigma and style are absent.

  4. They do not produce fruits. Only seeds are formed.

  5. Companion cells are absent.

  6. Sporophyll form the cones.

  7. Anther and filament are absent.

  8. The ovules are not present in the ovary.

  9. Gymnosperms do not possess flowers.

  10. Please read on the anatomical differences between gymnosperms and angiosperms here

The flower is the reproductive organ in plants' sexual reproduction. In order to achieve a successful sexual propagation or reproduction in plants, the floral parts of the flower are utilized.

The floral parts of a flower consists of the followings:

  1. Sepals

  2. Petals

  3. Stamen

  4. Carpel

The stamen is male portion of a plant. It consists of the anther and filament.

The carpel (or pistil) is the female portion of the plant. It consists of the stigma, style and ovary.

Please read more on plants' sexual reproduction here

An organism will be considered a pest if it does one of the followings:

  • Attack crops and eat its seeds, roots, stem, leaves and flowers. Examples are locust and grasshoppers.

  • Cause damage to stored food, fruits or other agricultural produce. Some may even urinate or deaficate on these products. Examples are rodents, cockroaches and mice.

  • Attack and kill farm animals like goats, sheep and cattle. Examples are foxes, wild cats and snakes.

  • Act as disease vectors. A vector is an organism that carries parasite and other disease causing organisms, without being affected; but when they introduce the parasites into their host, such host becomes infected with disease. Examples of vectors are rodents and mosquitoes.

    Please read more on vectors of diseases here.

Below are the classification of crops based on their uses:

  • Oil crops

  • Vegetable crops

  • Latex crops

  • Drug and Medicinal crops

  • Beverage crops

  • Fibre crops

  • Fruit crops

  • Root and Tubers

  • Legumes

  • Spices

  • Cereals

All crops are plants but not all plants are crops. Below are some instances:

  • Weeds are considered as plants, not crops.

  • Parasitic plants are not necessarily crops. Examples of parasitic plants include mistletoe, corpse flower and striga.

  • Carnivorous or insectivorous plants are not necessarily crops. Examples are sundew, venus flytrap and pitcher plant. The image below shows a carnivorous plant (venus flytrap).

Venus flytrap - Len Academy


Meanwhile, always understand that all crops are plants, and they are grown for food, money or something beneficial.

Please read on plants versus crops here