Lesson Notes By Weeks and Term v4 - SHS 2

Lesson Video

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Performance objectives

• Describe different methods of irrigation
• Explain the importance of drainage systems
• Identify common irrigation and drainage equipment
• Discuss the pros and cons of various irrigation methods

Lesson summary

In Ghana, our agriculture is heavily dependent on rainfall. We have two main seasons: the rainy season, when we plant most of our crops, and the dry season (Harmattan), when farming becomes very difficult due to lack of water. This reliance on rain limits our ability to produce food all year round, affecting food prices and the income of our farmers. Modern mechanised agriculture offers solutions to this challenge. This lesson focuses on two critical technologies: irrigation (supplying water to crops artificially) and drainage (removing excess water from the soil).

Lesson notes

Part A: Irrigation Systems What is Irrigation? Irrigation is the artificial application of water to land or soil to assist in the growing of agricultural crops. It is used to supplement rainfall, especially during periods of drought or in areas with low rainfall, like the Savannah regions of Ghana. Think of it as "man-made rain" for our farms. Uses and Importance of Irrigation in Ghana: Year-Round Farming: Enables farmers to cultivate crops during the dry season, leading to multiple harvests per year. Increased Crop Yield: Adequate water supply ensures that crops like maize, rice, and vegetables reach their full potential, increasing the yield per hectare. Cultivation in Arid Regions: Makes it possible to farm in dry areas of the country, such as the Upper East and Savannah regions, through projects like the Tono and Vea irrigation dams. Food Security: Ensures a consistent supply of food throughout the year, which helps to stabilise food prices in our markets. Growing Specific Crops: Some crops, like rice and sugarcane, require large amounts of water and can only be grown commercially with reliable irrigation. Methods of Irrigation

There are three main methods of irrigation used in modern agriculture.

a) Surface Irrigation This is where water is distributed over the soil surface by gravity. It is the oldest and one of the most common methods in Ghana, especially for small-scale farmers. How it works: Water flows from a higher point (like a canal or pump outlet) and spreads across the field. Types of Surface Irrigation: Furrow Irrigation: Water is channelled into small parallel trenches (furrows) made between rows of crops. The water seeps into the soil and spreads laterally to the crop roots. *Example:* Used for row crops like maize, tomatoes, and okra. Basin/Flood Irrigation: The entire field is flooded with water, which is held in a bunded area (basin). *Example:* Very common for rice cultivation in paddies, such as those at the Kpong Irrigation Project. Border Irrigation: The field is divided into long, parallel strips (borders) separated by small ridges. Water flows down these strips in a thin sheet. Advantages: Low initial cost and simple technology. Low energy requirement as it uses gravity. Disadvantages: Can be very inefficient; a lot of water is lost to evaporation and runoff. Requires a level or uniformly sloped piece of land. Can lead to waterlogging if not managed well.

b) 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: A pump supplies water under pressure through pipes to sprinkler heads, which spray the water into the air so it falls on the crops like rain. Example: Commonly used on commercial vegetable farms (e.g., cabbage, lettuce), school farms, and for irrigating sports fields. Advantages: More water-efficient than surface irrigation (about 75-85% efficiency). Suitable for most soil types and uneven terrain. Can be used for applying fertilisers and pesticides (fertigation). Disadvantages: Higher initial cost for pumps, pipes, and sprinklers. Requires a continuous energy source (electricity or fuel) to run the pump. Strong winds can distribute the water unevenly. Water can be lost to evaporation before it reaches the ground.

Evaluation guide

• Describe the methods and uses of irrigation AND drainage systems in
• Agricultural production.
• Experiential learning :
• Learners in mixed -ability groups visit a nearby farm with irrigation