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AGRICULTURAL SCIENCE JSS 2
WEEK 1
SOIL FERTILITY AND FERTILITY MANAGEMENT
LESSON: 1
SOIL FERTILITY: This is the ability of the soil to supply adequate major nutrients to
plants in a required quantity. Nutrients are essential elements for the plant body
to function well. They are called essential elements because without them the
crop will not grow well and may even die.
Plants nutrients are classed into;
1. Major(Macro) Nutrients: These are required by plants in relatively large
quantities. Examples; Nitrogen, Potassium, magnesium, calcium etc. Below are
some of the essential elements, their functions and deficiency symptoms (signs)
ELEMENTS, FUNCTIONS AND DEFICIENCY
ELEMENTS
Nitrogen
FUNCTIONS
Rapid plant growth and formation of
chlorophyll
Calcium
Neutralizes acidity in plants and
strengthen plant wall
Phosphorus Helps plants resist diseases and for
seed germination
Potassium Neutralizes organic acids in plants and
strengthen stem and stalk of plants.
Aids uptake of nitrate from the soil.
Magnesium Promotes formation of fat and oil.
Normal cell division and chlorophyll
Sulphur
Constitute plant protein, chlorophyll
formation and nitrogen fixation
DEFICIENCY SYMPTOMS
Stunted growth and
yellowing of leaves
Curling of leaves
Purple coloration of leaves
stunted growth
Yellowing between leaf
veins. Reduced plant
growth, seed and fruit
development.
Yellowing between leaf
veins and stunted growth.
Premature ageing of plant.
Stunted growth. Yellowing
of leaves
Micro or Minor Nutrients: These are needed in small quantities. They act as
coenzymes. Examples: iron, manganese, boron etc. Below are some of the
essential elements, their functions and deficiency symptoms (signs)
Element
Iron (Fe)
Manganese
and copper
Zinc
Boron
Molybdenum
Function
Chlorophyll formation and
protein synthesis
Protein and enzyme constituent.
And for photosynthesis
Growth of plant hormones.
Reproduction process.
Increase yield. Seed and fruit
formation
Nitrogen fixation and increased
soil pH level
Deficiency Symptoms
Restricted growth
Pale green colouration of leaves.
Death of young leaf tip.
Production of small leaves
Poor plant growth, reduced rate of
water absorption
Retarded growth and premature
flower drop.
Ways Of Maintaining Soil Fertility
1. Bush Fallowing: Bush fallowing is farming technique in which the farm land is
not cultivated for a period of time ,so that the soil nutrients can be replenished.
The soil is allowed to rest for sometimes before it is being used again. Farmers
adopt this method because it is simple, cheap and helps to check pests and
diseases. However, this is only possible where land is abundant. It discourages
land improvement.
2. Cover Cropping: This is the cultivation of fast growing crops that spread on the
soil surface to provide cover over the soil. Example: mucuna,centrosema
,calpogonium, pueraria stylosanthes etc. The crops prevent loss of nutrients
through erosion and evaporation of excess water. It also helps to fix atmospheric
nitrogen into the soil. However, they compete with other crops for nutrients.
3. Crop Rotation: Planting different types of crops on a piece of land every season
following a sequential order. The different crops grown during a given year or
season are collectively called COURSE.
4. Organic Manuring: This is the application of plant and animal residues to
improve the fertility of the soil. The various types include;
i. Green Manure:It is obtained by ploughing(turning)into the soil young plants
which decay to add to the soil nutrients.
ii. Compost manure: is obtained from the decaying of plant and animal materials
in a pit. iii. Farm yard manure: is a mixture of animal wastes with plant materials
used as animal bedding.
Organic manuring helps to check soil erosion, stimulate microbial activities
and conserve soil moisture. However, it is bulky and difficult to handle, the
quantity to be apply to crops is difficult to estimate.
5. Inorganic Manure/ Fertilizer: These are chemical substances which contain
plant nutrients. Types of inorganic manure include;
a. Simple or straight fertilizers:These contain only one major nutrients .Examples
are nitrogenous fertilizer(nitrogen), phosphatic fertilizerphosphorus )and potash
fertilizer(potassium).
b. Compound or mixed fertilizer: This contains two or more major nutrients in
different proportions. Examples are NPK fertilizer which contains Nitrogen,
Phosphorus and Potassium in the ratio 15:15:15.
Method of fertilizer application includes; broadcasting, ring method, foliar spray,
row side placement and top dressing. Organic fertilizer improves soil pH, and
improves soil structure. However, it lowers soil pH, reduces microbial activities in
the soil, and it is expensive to purchase.
6. Liming: The process of adding material rich in Calcium or Magnesium( such as
lime, wood ash etc) to the soil to reduce its acidity.
7. Mulching: This is the act of covering the soil surface with materials such as dry
grass, crop residues, polythene sheets etc to reduce the impact of rain and
sunlight on the soil.
Assignment.
a. Define the term soil fertility.
b. What is the difference between macro-nutrient and micro-nutrient ?
c. Why are some elements regarded as essential elements ?
Please submit the assignment to
MISS OGBA
through
( E-MAIL ADDRESS) [email protected]