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
Ø  It serves as habitat for some living organisms
Ø  It provides the nutrients requirement of plants
Ø  It support 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
Ø  Mineral components ( it consists of salt, silt and clay)
Ø  Soil water
Ø  Soil air
Ø  Organic matter
Ø  Soil Living organisms

PHYSICAL PROPERTIES OF SOIL
Ø  Soil Texture: This refers to the degree of coarseness or fineness of the soil particles
Ø  Soil Structure: This refers to the way in which the different soil particles are arranged. It gives the physical appearance of the soil.
Ø  Water Holding Capacity: This is the measure of the ability of a soil to retain water. It determines drainage through 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.
DIAGRAM:



Characteristics of each layer/ horizon
1.      Topsoil/Horizon A
Ø  It is rich in organic matter and microbes
Ø  It is dark in colour
Ø  Nutrients here can be leached to the sub-soil
Ø  It is usually less thick than sub-soil
2.      Sub-soil/ Horizon B
Ø  It contains less organic matter and microbes
Ø  Relatively thicker and less dark than the top-soil
Ø  It is usually reddish-brown in colour
Ø  Nutrients leached are deposited here
3.      Horizon C
Ø  It contains no organic matter and microbes
Ø  It contains weathered materials
Ø  Soil minerals occur in this layer
4.      Horizon D
Ø  It contains rocks which have not undergone weathering
Ø  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:
Ø  It is rich in soil nutrients and organic matter
Ø  It must contain useful soil organisms
Ø  It must have a good water holding capacity
Ø  It must have a suitable Ph
Ø  The texture must be loamy
·        
 SOIL FERTILITY: This refers to the ability of a soil to provide physical conditions and nutrients required for effective growth of a plant.

·         SOIL PRODUCTIVITY: This refers to the ability of a 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:
Ø  Crop removal
Ø  Leaching
Ø  Erosion
Ø  Bushfires
Ø  Overgrazing by cattle and other farm animals
Ø  Poor farming and tillage methods
Ø  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.
ü  Growing of cover crops
ü  Practicing crop rotation
ü  Application of organic and inorganic fertilizers
ü  Adding lime top the soil
ü  Practicing fallow cropping
ü  Strip cropping: This refers to the planting of crops along the contours of slope
ü  Terracing: This refers to leveling of hilly areas in the form of steps.
ü  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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