Virtual Kollage: Soil science

Posted by / Saturday, 14 May 2016 / No comments

Soil science



SOIL SCIENCE
Soil is the loose part of the earth’s crust that can support plant growth.

Importance of soil
 It serves as habitat for some living organisms

 It provides the nutrients requirement of plants

 It supports plants growth

Factors that influence the formation of soil

·         Topography of the land

·         Climate

·         Living organisms

·         Time

·         Human influence

·         Parent rock materials

  
COMPONENTS OF SOIL
Mineral components (it consists of salt, silt and clay)
Soil water
Soil air
Organic matter
Soil Living organisms

PHYSICAL PROPERTIES OF SOIL
Soil Texture: This refers to the degree of coarseness or the fineness of the soil particles
Soil Structure: This refers to the way in which the different soil particles are arranged. It gives the physical appearance of the soil.

Water Holding Capacity: This is the measure of the ability of soil to retain water. It determines drainage through the soil.

Characteristics
Sand
Clay
Loam
Particle size
Large
Small
Intermediate
Texture
Coarse- feels gritty when wet
Fine- feels sticky when wet
Intermediate
Air Space
Large
Small
Intermediate
Water Retaining Capacity
Low
High
Intermediate
Porosity
High
Low
Intermediate

SOIL PROFILE
This refers to the vertical cross-section of the soil which shows all the layers of the soil particles.

Characteristics of each layer/ horizon
1.      Topsoil/Horizon A
It is rich in organic matter and microbes
It is dark in colour
Nutrients here can be leached to the sub-soil
It is usually less thick than sub-soil

2.      Sub-soil/ Horizon B
It contains less organic matter and microbes
Relatively thicker and less dark than the top-soil
It is usually reddish-brown in colour
Nutrients leached are deposited here

3.      Horizon C
It contains no organic matter and microbes
It contains weathered materials
Soil minerals occur in this layer

4.      Horizon D
It contains rocks which have not undergone weathering
It contains no organic matter and microbes

IMPORTANCE OF SOIL PROFILE

·         It helps to determine the nutrient content of a soil

·         It helps to determine the soil type of a particular land

·         It helps the farmer to determine the crop suitable for a particular land

·         It helps to determine the susceptibility of a land to soil erosion

·         It enables the farmer to know the type of implement to use.

SOIL FERTILITY AND SOIL PRODUCTIVITY
A fertile soil is one that can provide adequate conditions and nutrients for effective growth of plant.
Features of a fertile soil:
It is rich in soil nutrients and organic matter
It must contain useful soil organisms
It must have a good water holding capacity
It must have a suitable Ph
The texture must be loamy

SOIL FERTILITY
This refers to the ability of soil to provide physical conditions and nutrients required for effective growth of a plant.

SOIL PRODUCTIVITY
This refers to the ability of soil to provide desired yield in the cultivation of a given plant when properly managed.

LOSS OF SOIL FERTILITY
The following are some of the ways through which a soil can lose its fertility:
Crop removal
Leaching
Erosion
Bushfires
Overgrazing by cattle and other farm animals
Poor farming and tillage methods
Surface mining and quarrying

MAINTENACE OF SOIL FERTILITY
In order to avoid soil losing its fertility, the farmer can undertake or carry out any of the following to preserve the fertility of the soil.

Growing of cover crops
Practicing crop rotation
Application of organic and inorganic fertilizers
Adding lime top the soil
Practicing fallow cropping
Strip cropping: This refers to the planting of crops along the contours of slope
Terracing: This refers to leveling of hilly areas in the form of steps.
Practicing mixed farming and mixed cropping

PLANT NUTRIENTS
These are substances that plants require in various quantities in order to grow. There are two types of nutrients. These are macronutrients and micronutrients.
a.       Macronutrients: These are the nutrients required in large amount for proper growth of the plant. Example Nitrogen (N), Potassium (K), Phosphorus (P), Calcium (Ca), Magnesium (Mg) and Sulphur (S).
b.      Micronutrients: These are the nutrients required in small amounts to support the growth of the plant. Example Boron (B), Manganese (Mn), Chlorine (Cl), Zinc (Zn), Copper (Cu) and Iron (Fe).

SOME ESSENTIAL NUTRIENTS FOR PLANT GROWTH
Nutrients
Functions
Deficiency
Nitrogen
Formation of proteins and chlorophyll
-          Small sized plants
-          Poor development
-          Yellowing of leaves
Phosphorus
Formation of energy compounds and acts as a buffer in the cell sap
-          Poor root development
-          Small sized plants
-          Mottling (colours of different shades)
Potassium
Formation of cell membranes and regulates certain metabolic processes in the cell
-          Red leaf coloration
-          Weak plants
-          Poor growth
Magnesium
Formation of chlorophyll
Yellowing of leaves
Iron
Formation of chlorophyll
Yellowing of leaves
Sulphur
Formation of protein
Slender stems and yellowing of leaves
Calcium
Formation of cell walls
-          Stunted growth
-          Poor roots development
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