Lesson Notes By Weeks and Term v4 - SHS 3

Lesson Video

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Performance objectives

• Identify and describe various irrigation systems.
• Demonstrate skills in using irrigation systems.
• Analyze the pros and cons of each method.
• Relate irrigation to community and agricultural productivity.

Lesson summary

In Ghana, our agriculture is heavily dependent on rainfall, which can be unpredictable. The long dry season (Harmattan) often brings farming activities to a halt, affecting food supply and farmers' incomes. Irrigation, the artificial application of water to crops, is a crucial technology that allows for year-round farming. It is a cornerstone of "New Dawn Agriculture," transforming farming from a seasonal activity into a reliable, all-year business. This lesson will introduce you to the various irrigation systems available, from simple manual methods to modern, large-scale technologies.

Lesson notes

A. What is Irrigation?

Irrigation is the controlled, 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 inadequate precipitation or drought. Think of it as giving your plants a drink of water when the sky doesn't provide it.

Importance in the Ghanaian Context: Year-Round Production: Enables farmers to cultivate crops during the dry season, leading to multiple harvests per year. Increased Crop Yields: Consistent water supply prevents water stress in plants, leading to healthier growth and significantly higher yields. Food Security: Ensures a stable supply of food for our population, reducing our reliance on imported food items. Cultivation of Water-Loving Crops: Allows for the commercial cultivation of vegetables (like tomatoes, peppers, cabbage) and fruits that require consistent moisture. Economic Empowerment: Provides a consistent income for farmers and creates jobs in manufacturing, installation, and maintenance of irrigation equipment. B. Major Types of Irrigation Systems

Here, we will explore the main systems mentioned in the NaCCA exemplar, from the simplest to the most advanced. Manual Irrigation Description: This is the most basic form, where water is carried and applied to plants by hand using tools like watering cans, buckets, or hoses. It is widely practised by small-scale vegetable farmers and backyard gardeners in Ghana. How it Works: The farmer fetches water from a source (well, stream, tank) and manually pours it at the base of each plant. Advantages: Very low initial cost. Simple and easy to implement. Water is applied directly where needed, reducing waste if done carefully. Disadvantages: Extremely labour-intensive and time-consuming. Not practical for large farms (more than an acre). Can lead to inconsistent watering. Surface Irrigation (Flood Irrigation) Description: In this system, water is distributed over the land by gravity. The entire surface of the soil is covered by a sheet of water. It is one of the oldest methods of irrigation. How it Works: Water is released from a channel at the higher end of a field and allowed to flow across the land. It can be managed in three main ways: Furrow Irrigation: Water flows in small channels (furrows) created between rows of crops. Common for maize, tomato, and yam. Basin Irrigation: The land is divided into small, level plots (basins) surrounded by bunds (small earth walls). The basin is then filled with water. Ideal for rice paddies and orchards on flat land. Border Irrigation: The land is divided into long, parallel strips (borders) separated by ridges. Water flows down these strips in a thin sheet. Advantages: Low initial and maintenance costs. Does not require high-tech equipment or high pressure. Low energy requirement as it relies on gravity. Disadvantages: High water loss due to evaporation and runoff (low water efficiency, often below 60%). Requires level or uniformly graded land. Can lead to waterlogging and soil salinity if not managed well. Sprinkler Irrigation Description: Water is pumped through a network of pipes and sprayed into the air through rotating heads called sprinklers, falling on the crops like artificial rainfall. How it Works: A pump provides pressure to force water through main lines, sub-lines, and finally out of the sprinkler nozzles. The spray pattern and coverage depend on the type of sprinkler head. Centre-Pivot: A long pipeline with sprinklers is mounted on wheeled towers that rotate around a central pivot point. This is used for very large, circular fields (e.g., commercial maize farms in the Afram Plains). Lateral Move: Similar to a centre-pivot, but the entire pipeline moves linearly across a rectangular field. Conventional/Solid Set: A fixed grid of pipes and sprinklers is laid out across the field and remains there for the season. Advantages: Suitable for most soil types, especially sandy soils. Can be used on uneven or rolling terrain where surface irrigation is not possible. More efficient water use than surface irrigation (75-85% efficiency). Disadvantages: High initial investment and energy costs (for pumping). Water can be lost to evaporation and wind drift on hot, windy days. Can promote fungal diseases on some crops as it wets the leaves. Drip or Trickle Irrigation (A form of Localised Irrigation) Description: This is the most efficient method of irrigation. Water is applied slowly and directly to the root zone of the plants through a network of pipes and small outlets called emitters or drippers. How it Works: Water flows at low pressure through plastic pipes laid along the crop rows. At each plant, an emitter releases water drop by drop. This "feeds the plant, not the soil." Advantages: Highest water efficiency (over 90%), minimising evaporation and runoff. Reduces weed growth as the area between plants remains dry. Fertilizers can be applied directly to the root zone with the water (fertigation). Reduces leaf diseases as foliage is kept dry. Ideal for fruit tree plantations (mango, orange, cocoa) and high-value vegetables. Disadvantages: High initial cost. Emitters can get clogged by sediment or algae, requiring good water filtration and regular maintenance. The pipe network can be damaged by farm machinery or rodents. Sub-irrigation Description: Water is applied below the ground surface, directly to the root zone. This is less common in open-field agriculture in Ghana but is used in specialised contexts. How it Works: A system of underground porous pipes or a controlled water table allows water to move upwards to the plant roots through capillary action. Advantages: Very high water efficiency with almost no evaporation loss. Keeps the soil surface dry, reducing weed growth. Disadvantages: Very high installation cost. Requires specific soil types and a high level of technical skill to design and manage. Risk of soil salinization.

Evaluation guide

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