Irrigation and Watering Techniques – SS1 Horticulture and Crop Production Lesson Note (First Term)

Irrigation is the artificial application of water to the soil to help crops grow. It lets farmers grow crops such as tomatoes, carrots and lettuce in the dry season, when rain cannot be relied on.

Behavioural objectives

By the end of the lesson, students should be able to:

1. explain why irrigation is needed in Nigeria;
2. describe surface, sprinkler and drip irrigation;
3. state the advantages and disadvantages of each method;
4. name simple tools for watering a small garden;
5. choose the right time of day and amount of water for sandy and clay soils;
6. list simple maintenance tasks for irrigation equipment.

Why do we need irrigation?

Irrigation is needed because rain does not fall all year, yet people need food all year round.

• Two seasons: Nigeria has a rainy season and a dry season, so crops cannot depend on rain alone.
• Insurance: It protects crops if the rains stop unexpectedly.
• All-year farming: It allows farmers to plant and harvest even in December and January.
• Better quality: Horticultural crops are mostly water, so steady watering makes them juicy and crunchy.
• Steady supply: Farmers can supply vegetables and fruit to the market when they are scarce.

What are the methods of irrigation?

There are three main methods of irrigation: surface, sprinkler and drip irrigation.

• Surface irrigation: water flows over the soil by gravity.
• Sprinkler irrigation: water is sprayed into the air like rain.
• Drip irrigation: water drips slowly to the roots of each plant.

What is surface irrigation?

Surface irrigation is the method in which water flows over the ground to the plants by gravity.

• It is the oldest and simplest method.
• Water is released at the top of the farm and flows down to the plants.

What are the types of surface irrigation?

There are two common types of surface irrigation: basin and furrow irrigation.

• Basin irrigation: a small “pool” or basin is made around the base of a tree, such as mango or citrus, and filled with water.
• Furrow irrigation: small trenches (furrows) are dug between the ridges of crops, and water flows along them to soak into the roots.

What are the advantages and disadvantages of surface irrigation?

• Advantage, low cost: it is very cheap because it needs no expensive pipes or pumps.
• Advantage, simple: farmers can learn and use it easily.
• Disadvantage, water loss: some water evaporates and some sinks too deep for roots to reach.
• Disadvantage, erosion: flowing water can wash away the topsoil.
• Disadvantage, slopes: it works poorly on steep or uneven land.

What is sprinkler irrigation?

Sprinkler irrigation is the method that pumps water through pipes and sprays it into the air through nozzles like rain.

• It is often called “artificial rain”.
• You may have seen a machine spinning and spraying water in a circle at a stadium or a large farm.

What are the advantages of sprinkler irrigation?

• Even coverage: it spreads water like natural rain over a large area.
• Good for slopes: it can be used on hilly ground without water running off to the bottom.
• Cooling: on very hot afternoons, it helps cool the air around the plants.

What are the disadvantages of sprinkler irrigation?

• High cost: the pipes and the pump are expensive to buy.
• Wind: strong winds blow the water away from the plants.
• Wet leaves: water on the leaves can encourage some diseases.

What is drip irrigation?

Drip irrigation is the method that delivers water slowly, drop by drop, directly to the roots of each plant.

• It is the most modern and efficient method.
• Tiny pipes with small holes (emitters) lie right next to the stem of each plant.

What are the advantages of drip irrigation?

• Water saving: it uses much less water than surface or sprinkler irrigation, because no water is wasted on empty space or weeds.
• Disease control: the leaves stay dry because water only reaches the roots, which discourages fungi that love wet leaves.
• Fertigation: liquid fertiliser can be mixed into the water so that it goes straight to the roots.

What are the disadvantages of drip irrigation?

• High cost: the pipes, emitters and tank cost more to set up.
• Blocking: the small holes block easily with sand, dirt or salt.
• Care needed: the pipes must be checked often for leaks and damage.

How do the three irrigation methods compare?

The table below compares the three methods already described.

What tools are used to water a small garden?

Small gardens are usually watered by hand with simple tools.

• Watering can: gives a gentle spray that suits seedlings and nursery beds.
• Bucket or calabash: carries water to beds and tree basins where there is no pipe.
• Hosepipe: reaches far beds quickly when there is a tap or pump.

What are the rules for watering?

Good watering depends on the right time, the right amount and the type of soil.

What is the best time to water plants?

• Best time: early morning (before 9 AM) or late evening (after 5 PM).
• Worst time: afternoon, because the sun evaporates the water before the plant can use it.
• Leaf damage: water left on leaves in strong afternoon sun may scorch them.

How should sandy and clay soils be watered?

• Sandy soil: needs small amounts of water very often, because it drains fast.
• Clay soil: needs larger amounts less often, because it holds water for a long time.
• Clay tip: apply water slowly so that it soaks in and does not run off.

How do we maintain irrigation equipment?

Irrigation equipment lasts longer and works better when it is checked and cleaned regularly.

• Clear the clogs: check the holes in drip pipes and sprinkler heads for sand or salt blocking them.
• Check for leaks: a leaking pipe wastes water and money, and creates a swampy spot that breeds mosquitoes.
• Clean the pump: keep a pump oiled and clean so that it does not break down in the middle of the season.

Evaluation

1. Define irrigation and give two reasons why it is important.
2. Describe basin irrigation and furrow irrigation.
3. State two advantages and two disadvantages of sprinkler irrigation.
4. Explain how drip irrigation controls disease and what fertigation means.
5. Why is afternoon the worst time to water plants?

Assignment

Write a watering plan for a school garden that has one sandy bed and one clay bed of tomatoes. In your plan:

1. choose one irrigation method and give two reasons for your choice;
2. say the best time of day to water and how often you would water each bed;
3. list two maintenance tasks for your equipment and say why each is needed.