IRRIGATION AND DRAINAGE

AGRICULTURAL SCIENCE FIRST TERM

E NOTES FOR SS 2

FIRST Term Agricultural Science

SS 2

Senior Secondary School 2

Subject : AGRICULTURAL SCIENCE

Topic :

IRRIGATION AND DRAINAGE

Class : SS 2

 TERM : FIRST  TERM  

WEEK : WEEK 6

LEARNING MATERIALS

• Whiteboard/Chalkboard
• Explanatory posters/pictures
• Explanatory videos
• Pictures of IRRIGATION AND DRAINAGE

Instructional Materials :

• Lagos State Scheme of Work.
• Online Materials.
• Textbooks
• Workbooks
• Pictures of different types of farm implements and tools

Previous Knowledge :

The pupils have been taught

SURVEYING AND PLANNING OF FARM STEAD

in their previous lesson

PERFORMANCE OBJECTIVES

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

• SAY THE MEANING OF IRRIGATION AND DRAINAGE
  
• MENTION TYPES OF IRRIGATION AND DRAINAGE
  
• WRITE OUT THE ADVANTAGES AND DISADVANTAGES OF IRRIGATION AND DRAINAGE

WEEK SIX 

TOPIC:

IRRIGATION AND DRAINAGE

WEEK SIX

TOPIC: IRRIGATION AND DRAINAGE

CONTENT

• Meaning 
• Types
• Advantages and Disadvantages

IRRIGATION 

This is the artificial application of water to soil or land for farming purposes.

FACTORS THAT DETERMINES IRRIGATION SYSTEM

1. Availability of water.
2. Slope of the land.
3. Soil type.
4. Type of crop.
5. Size of the farmland.

IMPORTANCE OF IRRIGATION IN CROP PRODUCTION

1. Irrigation softens the soil for tillage operations.
2. It provides moisture in the soil for root absorption.
3. It reduces the amount of salt accumulated in the top soil which could be injurious to the crops.
4. It cools the soil, thereby reducing soil, theory reducing soil temperature.
5. It enables crops to do well.
6. It increases crop productivity and yields.
7. It assists in production of crops all-round the year.
8. It helps in microbial decomposition and nutrient release to the soil.
9. It dissolves soil nutrient for root absorption.

NEGATIVE EFFECTS OF IRRIGATION

1. It provides humid environment which favours the buildup of pests and diseases. 
2. It encourages the spread of weeds seeds.

TYPES OF IRRIGATION SYSTEMS   

The three types of irrigation systems are:

1. Surface irrigation 
2. Sub-surface irrigation 
3. Overhead irrigation

SURFACE IRRIGATION

In this system, water from rivers, dams or stream flows along the surface of the land to the farmland. This can be in form of channels, flooding, contour ditch, furrow, basin etc. This type of irrigation requires a gentle slope to be successful.

ADVANTAGES OF SURFACE IRRIGATION

1. It removes excess water caused by heavy rainfall.
2. It is easier to establish or setup. 
3. It is cheap to maintain.
4. It prevents accumulation of alkali.
5. It increases activities of microbes in the too soil.

DISADVANTAGES OF SURFACE IRRIGATION

1. It cannot be practiced where land is hilly. 
2. It cannot be successful in a sandy soil.  
3. The volume of water, especially in flooding may be difficult to control.
4. Some crops may not tolerate heavy flooding.

SUB SURFACE IRRIGATION

In this system, water is applied below the soil surface. It involves the use of perforated pipes to deliver the water within the soil. This water gets to the root through capillary action.

ADVANTAGES OF SUBSURFACE IRRIGATION

1. It is possible to maintain water at optimum depth for crop need.
2. Water used efficiently.
3. It ensures low evaporation loses from the soil.
4. It does not create obstruction when carrying out cultural practices.

DISADVANTAGES OF SUBSURFACE IRRIGATION

1. Water with high salt content cannot be used.
2. It requires some level of expertise or technical-know-how.
3. It is a bit expensive.

OVERHEAD IRRIGATION

In this system, water is supplied to the farmland above the surface of the soil.

PROBLEMS ASSOCIATED WITH OVERHEAD IRRIGATION 

1. Wind can cause uneven distribution of water by distorting sprinkler pattern.
2. The spray force can damage ripening of soft fruits.
3. A stable water supply is needed for economic use of the equipment.
4. The initial investment is usually high.
5. Power requirement for pumping water is high.
6. Requires technical-know-how.
7. It can spread diseases.
8. Laterals pipes hinder the movement of farm machines.
9. High cost of maintenance, repair and spare parts.

There are two types of overhead irrigation:

1. Drip irrigation
2. Sprinkler irrigation 

SPRINKLER IRRIGATION

In this system, water is sprayed from the air and allowed to fall on the ground like rain through nozzle under pressure.

ADVANTAGES OF SPRINKLER IRRIGATION

1. The amount of water supplied is regulated.
2. It economizes the use of water.
3. It is suitable for arid lands with high evaporation transpiration rate.
4. It can be used for all crops except tree crops.  
5. Soluble fertilizers and herbicides can be applied through the irrigation water.

DISADVANTAGES OF SPRINKLER IRRIGATION

1. Sprinkler irrigation is costly to operate.
2. High wind velocity may prevent distribution of water.
3. A stable water supply is required. 
4. It requires high power to produce the high pressure needed to pump water into pipes.
5. There is lack of sufficient technical know-how on sprinkle irrigation. 

DRIP IRRIGATION

Drip irrigation is a method whereby water is discharged through nozzles called emitters or drippers at selected spacing to deliver water to the soil surface near the best of the plant.

ADVANTAGES OF DRIP IRRIGATION

1. It is economical in the use of water.
2. It reduces salt concentration in the root zone.
3. Fertilizers can be applied through the system.
4. It operates with slower and arid areas.

DISADVANTAGES OF DRIP IRRIGATION

1. It is very expensive to set up and maintain.
2. Water cannot be distributed in a sloppy farmland evenly.
3. Water with high salt content can be used.

PROBLEMS ASSOCIATED WITH IRRIGATION

1. Inadequate water supply for irrigation.
2. Irrigation equipment is expansive.
3. Pests from surrounding may invade irrigated areas and damage crops.
4. Disease causing organism increase with increased humidity.
5. Vectors eg. Snails and tsetse flies breed freely in irrigation areas.
6. Lack of technical-know-how.
7. Excessive dissolution of salt affects crops.
8. It disturbs free movement of farm machinery. 

HOW TO REDUCE DISEASE BUILD UP IN IRRIGATION FARM

1. Use of disease-resistant varieties.
2. Crop rotation.
3. Use of appropriate chemicals.
4. Use of clean tools.
5. Use of clean or healthy planting materials. 
6. Destruction of infected crops to prevent spread of diseases.
7. Avoidance of excessive irrigation.
8. Weed control.

DRAINAGE

Drainage is the process whereby excess water in the soil is removed artificially to promote good farming activities.

IMPORTANCE OR EFFECTS OF DRAINAGE

1. It helps in regaining water logged soil for crop production.
2. It improves soil structure and water holding capacity of the soil.
3. It improves soil aeration for good root respiration.
4. It gives suitable condition for the growth of microbes which helps in decomposition.
5. It helps to increase soil temperature.
6. Drainage leaches excess salt from the soil which prevent poisoning and death of the plants.
7. It makes tillage operation easier.
8. It reduces incidence of crop diseases. 
9. It enhances harvest of crops e.g swamp rice.
10. It enhances early planting of crops.
11. It makes land preparation easier.
12. It reduces soil acidity.
13. It increases soil temperature.
14. It increases crop production. 
15. It makes soil workable soil and light.
16. It reduces soil salinity.

TYPES OF DRAINAGE

1. Surface drainage
2. Sub-surface drainage

SURFACE DRAINAGE

This involves the orderly removal of excess water artificially from the surface of the land using constructed open ditches, field drains and land grading.

ADVANTAGES OF SURFACE DRAINAGE

1. It is relatively easy to construct.
2. It is cheaper than the sub surface drainage system.

DISADVANTAGES OF SURFACE DRAINAGE

1. It occupies good land (space) that could have been use for planting. 
2. It hinders the passage of machines like tractor.
3. It is prone to gully erosion.
4. It requires frequent maintenance.
5. It increases the cost of production. 
6. Farm mechanization is impaired.
7. It is expensive and difficult to establish.

SUB SURFACE DRAINAGE

This is the orderly removal of excess water from the land using tiles or moles or perforated pipes dug under the ground, it is also called underground drainage.

ADVANTAGES OF SURFACE DRAINAGE

1. It does not pose any threat to machines.
2. High values of crops are grown.
3. It leaves the field free from surface obstruction.
4. More land is made available for cultivation.
5. Cost of maintenance is low.
6. Drainage is faster and more efficient.

DISADVANTAGES OF SUBSURFACE DRAINAGE

1. It is very expensive to operate.
2. It cannot easily be constructed. 
3. It is difficult to maintain.
4. It needs very deep excavation of the soil.

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. What is irrigation?
2. List two negative effects of irrigation.
3. Describe surface and sub-surface irrigation.
4. Discuss the two types of overhead irrigation.
5. List five problems associated with irrigation.
6. List four things that can be done to reduce disease build up in an irrigation farmland.
7. What is irrigation?
8. List four importance of irrigation in crop production.
9. List the three types of irrigation system.
10. What is farm machinery?
11. List five tractor couple implements.
12. State and explain the two systems of drainage.

Part B Objectives 

1. Artificial application of water to the farmland is _____ (a) irrigation (b) wetting (c) drainage (d) harvesting

1. Excess water is conducted away from the soil through ____ (a) irrigation  (b) wetting (c) drainage (d) planting
2. The type of irrigation which can be done on a gentle slope is ____ (a) surface irrigation (b) subsurface irrigation (c) overhead irrigation (d) Sprinkler
3. The machine which is used to hatch eggs is ____ (a) tractor (b) incubator (c) milking machine (d) plough
4. The tool used in transplanting is ______ (a) cutlass (b) hoe (c) hand trowel (d) tractor

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