SOIL-DEFINITION, TYPES AND PROPERTIES-BY INSTRUCTOR MRS. EREKATA, O.J
DEFINITION OF SOIL: Soil can be defined as the uppermost layer of the earth’s crust which supports plant growing and the survival of animals. Plants have their roots and they obtain water and mineral nutrients from soil. Soil is formed from rocks by a process known as WETHERING. The soil is divided into three layers:
TOP SOIL: [Soil surface] This is where most plants roots are found. The top soil is much darker than the soil beneath.
SUB SOIL: This is found below the top soil and it is relatively infertile.
PARENT ROCK: This is found below the sub soil. These three layers that is top soil, subsoil and the parent rock together form the soil profile.
COMPOSITION OF SOIL: A good soil consists of the following components.
A] Mineral/inorganic matter———-45%
B] Organic matter————————05%
C] Soil water——————————-25%
D] Soil air———————————–25%
E] Living organisms———————–insignificant
IMPORTANCE OF SOIL ORGANIC MATTER: The importance of soil organic matter are as follow:
They help to maintain good soil structure.
They supply nutrients to plants.
They provide energy for activity of micro-organism in the soil.
They regulate soil temperature.
They improve air and water holding capacity of the soil.
IMPORTANCE OF SOIL AIR: The importance of soil air are:
It provides oxygen for the respiration of living organism in the soil.
It aids seed germination.
IMPORTANCE OF SOIL WATER: The importance of soil water are:
It dissolves the plant nutrients.
It regulates soil temperature.
It is needed for photosynthesis.
It encourages the activities of enzymes in the soil.
MAJOR TYPES OF SOIL—BY INSTRUCTOR MRS. EREKATA, O.J.
There are three major types of soil which are:
A] SANDY SOIL: A soil is said to be sandy when the proportion of the sand particles in the sample is more than other particles. It has the following characteristics.
1. It has coarse particles texture.
2. It has large pore spaces.
3. It is not sticky when wet.
4. It is well drained, dry out quickly and easy to work.
5. It has poor water holding capacity.
B] CLAY SOIL: It has the following properties.
1. The soil particles are fine and very tiny.
2. It is sticky when wet and could be molded into any shape.
3. It is poorly drained and support water logging.
4. It has high water holding capacity.
5. It is heavy to work on but rich in nutrients.
C] LOAMY SOIL: The soil is formed from the combination of sandy soil and dry soil with a proportion of organic matter. The soil is very fertile and is considered to be the best soil for Agriculture.
CHARACTERISTICS OF LOAMY SOIL: It has the following characteristics-
It contains a lot of organic matter.
It is loose and moist in nature.
It is well aerated and can hold water.
It does not support erosion and water logging.
It is easy to cultivate.
SOIL PROPERTIES: These include the following:
A] SOIL TEXTURE: Soil texture refers to the relative proportion or sizes of the various particles of the soil. In other words, it refers to the degree of fineness or coarseness of the various soil particles. It is the percentage of sand, silt and clay in a soil. Soil texture can be determined by various methods, these methods include.
1. By feeling- Take a little sample of soil and rub them between the fore-finger and the thumb. A sharp feel represents the presence of sand while a smooth or powdery feel represents the presence of dry.
2. By Sieving- The various sizes represent in a sample of dried soil can be separated by putting the sample into a series of various measured mesh diameters and shaking vigorously.
3. By sedimentation: A sample of soil is placed inside a glass jar and large volume of water is added and the mixture is vigorously shaken and allowed to settle. At the end, large particles like coarse sand and gravel settle at the bottom while the organic material floats on top of the water in the glass jar.
4. By molding: Mix a sample of soil with little water and try to mold the mixture if the mixture is sticky, it shows that clay is present but if it is not sticky and cannot be molded, it shows that sand is present.
IMPORTANCE OF SOIL TEXTURE.
It enables the farmer to know the type of soil in his farmland.
It determines the type of crop to grow on the land.
It supports soil micro-organism essential for plant growth.
It determines the movement of air and water.
B] SOIL STURCTURE: Soil structure refers to the ways in which the different particles of the soil are packed or arranged. Soil structure has a direct effect on crop yield. If the soil structure is good, air will circulate well while water-logging, erosion and leaching will be reduced. The structure of the soil can be preserved by the following ways.
1. Plant cover crops
3. Applying manure
4. Avoiding over-grazing and erosion.
C] SOIL TEMPERATURE. This refers to the temperature within the soil. It is the degree of hotness or coldness of the soil. Soil temperature affects the formation of soil organic matter. It also aids seed germination.