Lesson Notes By Weeks and Term v4 - SHS 3

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Performance objectives

• Identify and describe at least four types of irrigation systems.
• Demonstrate setting up a simple irrigation system.
• Explain the advantages and disadvantages of each method.
• Relate irrigation systems to Ghanaian community farming.

Lesson summary

Welcome, future leaders in agriculture! Today, we are exploring a topic that is critical for Ghana's food security and economic prosperity: Irrigation. In a country like ours, where rainfall can be unpredictable, especially with changing climate patterns, irrigation is not just a technique; it is a lifeline for our farmers. It allows for year-round cultivation, turning farming from a seasonal activity into a full-time, profitable business. This lesson will move beyond simply watering plants; we will delve into the science and technology—the "machinery"—that makes modern, efficient farming possible, particularly for high-value crops like mangoes, oranges, and cashews.

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 during periods of drought or in arid and semi-arid regions like the northern parts of Ghana. Essentially, irrigation is about giving crops the right amount of water, at the right time, to ensure maximum growth and yield.

Why is it crucial for Ghana? Climate Variability: Ghana has distinct wet and dry seasons. The northern savannah regions experience a long, harsh dry season (Harmattan), making farming impossible without irrigation. Food Security: Irrigation enables year-round food production, reducing our reliance on imported food items and stabilising food prices in the market. Economic Empowerment: It allows farmers to cultivate high-value crops like vegetables and fruits during the dry season, providing a consistent source of income and creating jobs. Plantation Crops: For perennial crops like cocoa, mango, and oil palm, irrigation during establishment and dry periods significantly improves survival rates and yields. B. Types of Irrigation Systems

These systems are forms of agricultural technology or machinery, involving components like pumps, pipes, valves, and emitters to control water flow. Surface Irrigation This is one of the oldest methods. Water is distributed over and across the land by gravity, flowing from a higher point to a lower point. How it works: Water is released from a channel or pipe at the top of a field and allowed to flow down the slope. Forms: Flood/Basin Irrigation: The entire field is covered with a sheet of water, like in a rice paddy. Furrow Irrigation: Water is channelled into small, parallel ditches (furrows) created between rows of crops. The crops are planted on the ridges. Machinery/Components: Siphons, gates, pipes, and sometimes land-levelling equipment. Advantages: Low initial and operational cost. Simple technology, easy to manage. Disadvantages: Very inefficient; up to 50% of water is lost to evaporation and runoff. Requires a level or uniformly sloped piece of land. Can lead to waterlogging and soil salinity if not managed well. Ghanaian Context: Commonly used for rice cultivation in areas like the Kpong and Tono Irrigation Projects. Also used by some vegetable farmers for crops like cabbage and lettuce. Sprinkler Irrigation Water is piped to one or more central locations within the field and distributed by overhead high-pressure sprinklers or guns. It mimics natural rainfall. How it works: Water is pumped through a network of pipes and sprayed into the air through rotating sprinkler heads, falling onto the crops like rain. Machinery/Components: A pump, main pipes, lateral pipes, and sprinkler heads. Forms: Centre-pivot: A long pipe with sprinklers mounted on it rotates around a central pivot point, irrigating a large circular area. Lateral move: Similar to centre-pivot, but the pipe moves laterally across a rectangular field. Advantages: More efficient than surface irrigation (around 75-85% efficiency). Suitable for a wide range of soil types and terrains. Can be used to apply fertilisers and pesticides (fertigation/chemigation). Disadvantages: High initial cost for pumps and pipes. Requires a reliable energy source (electricity or fuel) to operate the pump. Water can be lost to evaporation and wind drift in hot, windy conditions. Ghanaian Context: Used on large commercial farms, school farms, and for irrigating sports fields and lawns. Ideal for large-scale maize, vegetable, or pineapple plantations. Drip (or Trickle/Localised) Irrigation This is the most efficient water and nutrient delivery system for growing crops. How it works: Water is delivered slowly and directly to the root zone of each individual plant through a network of pipes, tubes, and emitters (drippers). Machinery/Components: Pump, filters (very important to prevent clogging), mainlines, sub-mains, lateral lines, and emitters/drippers. Advantages: Highest water efficiency (over 95%). Minimises evaporation and runoff. Reduces weed growth, as water is only applied where needed. Reduces the incidence of fungal diseases that thrive on wet leaves. Precise application of water and nutrients (fertigation). Disadvantages: Very high initial installation cost. Emitters can easily get clogged by sand or salt particles, requiring good filtration and maintenance. Pipes can be damaged by farm equipment or rodents. Ghanaian Context: The best choice for high-value fruit tree enterprises (mango, citrus, papaya) and vegetable farming (tomatoes, peppers, cucumber). Many commercial farms on the Accra Plains use this system. Simple "bucket drip kits" are also becoming popular for small-scale farmers. Sub-irrigation Water is applied below the ground surface, either by raising the water table or by using a buried pipe system. How it works: Water is delivered to the plant root zone from below, through buried perforated pipes or by managing the water table to keep it at an optimal level. Advantages: Very low water loss from evaporation. Keeps the soil surface dry, reducing weed growth. Disadvantages: Requires specific soil types and water table conditions. High installation cost and potential for drainage problems. Not common in Ghana due to its complexity and specific requirements. Manual Irrigation This is the simplest form, relying on human labour to carry and apply water. How it works: Using watering cans, buckets, or simple hoses to water plants individually or in small groups. Machinery/Components: Buckets, watering cans, hoses. Advantages: Extremely low cost. Precise application of water, though labour-intensive. Ideal for small gardens, nurseries, and backyard farms. Disadvantages: Very labour-intensive and time-consuming. Impractical for any farm larger than a small plot. Ghanaian Context: This is the most common method used in backyard vegetable gardens and small-scale farms across the country. Every student who has a small garden at home has practised this.

Evaluation guide

• Demonstrate knowledge
• and skills in the use of
• various forms of irrigation
• systems in plantation and