PLANT NUTRIENTS AND NUTRIENT CYCLES

 

 

AGRICULTURAL SCIENCE FIRST TERM

 

E NOTES FOR SS 2

 

FIRST TERM AGRICULTURAL SCIENCE 

SS 2

 

Senior Secondary School 2

 

Subject : AGRICULTURAL SCIENCE

 

Topic :

PLANT NUTRIENTS AND NUTRIENT CYCLES

 

Class : SS 2

 

 

 TERM : FIRST  TERM  

 

 

WEEK : WEEK 8

 

 

LEARNING MATERIALS

• Whiteboard/Chalkboard
• Explanatory posters/pictures
• Explanatory videos
• Pictures of PLANT NUTRIENTS AND NUTRIENT CYCLES

Instructional Materials :

• Lagos State Scheme of Work.
• Online Materials.
• Textbooks
• Workbooks
• Pictures of PLANT NUTRIENTS AND NUTRIENT CYCLES

 

 

Previous Knowledge :

The pupils have been taught

 

 

  ENVIRONMENTAL FACTORS AFFECTING AGRICULTURAL PRODUCTION

 

 

in their previous lesson

 

PERFORMANCE OBJECTIVES

By the end of the lesson , learners will  be able to

• SAY THE MEANING OF PLANT NUTRIENTS AND NUTRIENT CYCLES
• MENTION THE CLASSIFICATION OF PLANT NUTRIENTS AND NUTRIENT CYCLES
  
• STATE THE FUNCTIONS OF EACH CLASS OF NUTRIENTS
• LIST THE DEFICIENCY SYMPTOMS OF LACK OF NUTRIENTS
• EXPLAIN NITROGEN CIRCLE

 

WEEK EIGHT

TOPIC: PLANT NUTRIENTS AND NUTRIENT CYCLES

CONTENT

• Classify plant nutrients
• Functions and deficiency symptoms of nutrients
• Nutrient cycles

 

PLANT NUTRIENTS AND NUTRIENT CYCLES

Plant nutrients are classified into two, these includes macronutrient and micronutrient.

 

MACRONUTRIENTS

These are mineral elements or nutrients required by crops in large quantities. Examples are: nitrogen, phosphorus, potassium, magnesium, calcium and sulphur.

 

MICRONUTRIENT OR TRACE ELEMENTS

These are mineral elements or nutrients required by crops in small quantities. Examples are: Zinc, Copper, boron, molybdenum, Iron, Chlorine and Manganese.

 

FUNCTIONS AND DEFICIENCY SYMPTOMS OF PLANT NUTRIENTS

S/N	ELEMENT	FUNCTION	DEFICIENCY SYMPTOMS
1.	Nitrogen	Aids plant’s growth and reproduction Promotes vegetative and short system growth Excess Nitrogen delay maturation and fruiting Promotes chlorophyll formation Necessary for synthesis of plant hormones	Stunted growth  Yellowing of leaves Leaves tend to drop Poor formation of fruits and flowers
2.	Phosphorus	It aid enzyme reactions It is a constituent of cell division Increases soil resistant to diseases Helps in ripening of fruits Help in root development and seed germination Aids seed germination	Logging results in cereal crops Stunted growth Leaves turn purple and brownish in colour Poor root development  Immature fruit drop
3	Potassium	Important constituent of plant tissues Aids synthesis of carbohydrates Activates various plant enzyme reactions Promotes development of young plants  Helps in nitrate uptake in the soil	Weak slender stems Delayed growth Premature loss of leaves Brown colour at margin of leaves
4	Calcium	Strengthens plant cell with calcium pectate Helps in translocation and storage of carbohydrate and proteins in seeds and tubers Necessary for normal growth of root tips It controls toxicity of aluminum, manganese and sodium ions It improves soil PH	Causes stunting of root system Weak slender plants Pale yellow colour of leaves
5	Magnesium	It is important in the synthesis of carbohydrate as it is a constituent of chlorophyll  It assists in transportation of phosphate for fruit seeds development It enhances plant growth It is required for normal cell division Necessary for synthesis of soil in plants	Chlorosis along leaf veins  Stunted growth Premature leaf fall

 

NITROGEN CYCLES 

Nitrogen cycles refer to the circulation of certain nutrients like nitrogen, carbon and water in nature.

Nitrogen cycle is the nature’s way of regulating the amount of Nitrogen in the soil and air

 

Ways by which Nitrogen is added to the soil in Nitrogen Cycle

1. Direct fixation by lightening during rainfall.
2. Incorporation into the soil by free living bacteria or non-symbolic bacteria.
3. Nitrogen fixing bacteria in the root nodules.
4. Decomposition of organic matter.
5. Application of Nitrogen fertilizer. 
6. Ammonification.
7. Nitrification. 

 

Soil can gain Nitrogen through the following ways

1. Symbiotic Nitrogen Fixation
2. Electrical discharge 
3. Non symbiotic Nitrogen Fixation
4. Ammonification and Nitrification 
5. Application or organic manure and Nitrogen fertilizers

 

Ways by which nitrogen is lost from the soil are:  

1. By Denitrification
2. Soil erosion
3. Leaching
4. Soil PH
5. Bush burning
6. Crop removal
7. Volatilisation
8. Oxidation reaction
9. Reduction reaction

 

Processes that lead to formation of Nitrate from organic matter in Nitrogen Cycle

1. Putrefaction: Delay of plant and animal remains into similar nitrogenous compounds by microorganism
2. Amminization: Products from putrefaction reactions converted to simple amino compounds and animal
3. Ammonization:  Conversion of amino compounds and amines into ammonium compounds
4. Nitrification: Oxidation of ammonium compounds into nitrites and Nitrates

 

CARBON CYCLE

This involves the series of processes which contribute to the circulation of carbon in nature.

 

Explanation

1. Carbondioxide is removed from the air mainly by photosynthesis
2. Carbon is lost in form of carbonates of calcium and magnesium through leaching and drainage.

The atmosphere gains carbondioxide through

1. Burning of fuel like coal and wood
2. The action of volcanoes which releases carbon dioxide 
3. The respiration of plants and animals 
4. Death and delay and putrefaction of plants and animals
5. Diffusion of carbon dioxide from seas and other bodies of water

 

IMPORTANCE OF CARBON CYCLE

1. Plant use carbondioxide obtained from the air to manufacture their food during photosynthesis
2. Provision of carbon which is the essential building block of all organic matters
3. Organic matter which is made from carbon helps to replenish soil nutrients.

 

WATER CYCLE

This is the continuous movement of water from the atmosphere to the earth and from the earth to the atmosphere.

 

The atmosphere receives water through 

1. Evaporation from oceans and land 
2. Transpiration from plants
3. Breathing and respiration by plants and animals

 

Land receives water through:

1. Rainfall and precipitation
2. Infiltration and percolation 

 

FORMS IN WHICH WATER EXISTS IN THE SOIL 

1. Hygroscopic water
2. Capillary water
3. Gravitational water

 

Ways of conserving water in the soil 

1. Stoppage or reduction of water-run-off
2. Addition of humus or organic mature 
3. Removal of weeds to reduce transpiration and water loss
4. Mulching
5. Cover cropping
6. Contour ridging
7. Appropriate tillage
8. Strip cropping 

 

IMPORTANCE OF WATER TO CROPS

1. Water provides the medium for absorption of minerals salts
2. It facilitates transfer of nutrients to other parts of plants 
3. It is an essential raw material during photosynthesis
4. Facilities enzymatic activities occurring in crop plant protoplasm
5. It is a constituent of protoplasm
6. It has cooling effect on crops
7. It helps to sustain life
8. It helps in seed germination
9. It helps to maintain plant turgor or turgidity

 

 

 

 

Presentation

The topic is presented step by step

 

Step 1:

The class teacher revises the previous topics

 

Step 2.

He introduces the new topic

 

Step 3:

The class teacher allows the pupils to give their own examples and he corrects them when the needs arise

 

 

 

EVALUATION

1. Give five examples each of macro and micro nutrients.
2. State the functions and deficiency symptoms of sulphur, iron, manganese copper, zinc, boron and molybdenum.
3. List five importance of water to crops.
4. List three form which water exist in the soil.
5. List three ways by which Nitrogen is lost from the soil.
6. What is macro nutrient? List five examples.
7. What are micronutrients? List five examples.
8.  Differentiate between macro and micro nutrients
9.  List three factors influencing nutrient availability in the soil
10. State three function of Nitrogen to plants

Part B Objectives 

1. The following are climate factors except (a) soil types (b) humidity (c) temperature (d) light
2. Which of the following is not an edaphic factor (a) soil PH (b) soil fertility (c) soil water (d) topography
3. The following are types of erosion except ____ (a) splash (b) rill (c) sheet (d) mulch
4. The washing away of soil nutrients down beyond the reach of the root is ___ (a) erosion (b) leaching (c) mulching (d) staking
5. High humidity is responsible for ____ (a) dryness (b) water logging (c) rainfall (d) erosion
6. Explain Nitrification.
7. List five ways the soil can gain nitrogen.
8. The conversion of nitrates to nitrogen gas by certain bacteria is ___ (a) oxidation (b) reduction (c) nitrification (d) de-nitrification
9. Microbial delay of plant and animal remains into simpler nitrogenous compound is ___ (a) nitrification (b) putrefaction (c) leaching (d) burning
10. The washing away of soil nutrient down beyond the reach of the root is called ___ (a) erosion (b) mulching (c) leading (d) fertilization
11. The following are macro nutrients expect (a) boron (b) nitrogen (c) magnesium (d) calcium
12. Which of these is not a micro-element? (a) copper (b) zinc (c) boron (d) potassium

 

 

 

 

Conclusion :

 

The teacher summarize the lesson. He or she gives out a board summary of the topic as note .

He or she goes round to mark and does the necessary corrections