Lesson Notes By Weeks and Term v4 - SHS 1

Lesson Video

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Performance objectives

• Describe at least three modern methods of crop irrigation.
• Explain the advantages and disadvantages of each method.
• Analyze which irrigation systems are best for specific crops.
• Identify irrigation systems used on local Ghanaian farms.

Lesson summary

In Ghana, our agriculture is heavily dependent on rainfall, which can be unreliable, especially with changing climate patterns. This makes farming during the long dry season very difficult, leading to food shortages and high prices. Modern irrigation provides a solution by allowing farmers to supply water to their crops efficiently, anytime they need it. This lesson will move beyond the traditional watering can and flood methods to explore modern, water-saving technologies like drip and sprinkler systems.

Lesson notes

A. What is Irrigation?

Irrigation is the artificial application of water to land or soil to assist in the growing of crops. It is used to supplement rainfall, especially in areas or during seasons when rainfall is insufficient for crop growth. Traditional Methods in Ghana: Many small-scale farmers still use methods like the watering can, buckets, or flood irrigation (diverting water from a stream to flood the entire field). While these methods work, they are often labour-intensive and waste a lot of water through evaporation and runoff. Modern Methods: Modern methods focus on efficiency – using the least amount of water and energy to get the best results. We will focus on two major types: Drip and Sprinkler irrigation. B. Drip Irrigation (or Trickle Irrigation)

This is one of the most efficient methods of irrigation. It involves the slow, precise application of water directly to the root zone of the plants. How it Works: Water is delivered through a network of plastic pipes and tubes. At specific points along the tubes, small devices called emitters or drippers release water drop by drop, right where the plant needs it most. Key Components: Water Source: A borehole, well, river, or storage tank (e.g., Polytank). Pump: To create the necessary pressure to push water through the pipes. For a simple gravity-fed system using an elevated tank, a pump may only be needed to fill the tank. Filtration System: Crucial for removing sand, silt, and debris from the water to prevent the tiny emitters from clogging. This is the heart of a good drip system. Mainline Pipe: The main pipe that carries water from the source to the field. Sub-main Pipes: Smaller pipes branching off the mainline to distribute water to different sections of the field. Lateral Lines: Even smaller tubes that run along the rows of crops. The emitters are attached to these laterals. Emitters (Drippers): The devices that release water slowly to the plant roots. Advantages of Drip Irrigation: High Water Efficiency: Reduces water loss from evaporation and runoff by up to 95%. This is perfect for dry regions like the Upper East or Northern Regions. Reduced Weed Growth: Water is only applied to the crop's root zone, so the areas between the rows remain dry, suppressing weed growth. Fertigation: Liquid fertilisers can be mixed with the irrigation water and delivered directly to the roots, saving labour and fertiliser costs. Reduced Soil Erosion: The slow application rate prevents water from washing away the topsoil. Less Disease: Plant leaves remain dry, reducing the risk of fungal diseases that thrive in moist conditions. Disadvantages of Drip Irrigation: High Initial Cost: The cost of pipes, filters, and emitters can be high for large farms. Clogging: Emitters can easily get blocked by dirt or mineral deposits if the water is not filtered properly. Maintenance: Requires regular checks to ensure emitters are working correctly. Damage: Pipes can be damaged by farm machinery or rodents.

Ghanaian Context Example: A tomato farmer in Navrongo during the dry season would benefit greatly from drip irrigation. It would conserve precious water from their dugout or borehole and ensure each tomato plant gets exactly what it needs without wasting a drop. C. Sprinkler Irrigation

Evaluation guide

• Describe the modern and efficient ways of crop irrigation
• Structured Talk -for-Learning: In mixed -gender groups, learners brainstorm on modern
• methods of supplying water to vegetable crops and ornamental plants (e.g. use of drip irrigation,
• and sprinkler irrigation) after watching a PowerPoint presentation on modern forms of