Factors which influence the practice of irrigation include all except

Step 1: Analyze the question The question asks which option is NOT a factor influencing irrigation. Irrigation is the artificial supply of water to farmland, so we are looking for the option that would discourage or remove the need for irrigation.

Step 2: Explain the concept Irrigation is practised when natural water supply is not enough for crop growth. Factors that encourage it include:

• Low, seasonal, or unreliable rainfall, since crops need water supplied artificially.
• A need to increase food production, which allows farming all year round (dry-season farming).
• Fertile soil, which makes the investment in water worthwhile because crops will yield well.
• Availability of water sources such as rivers, dams, or boreholes.

Step 3: Evaluate each option

• A. Unreliable rainfall: This is a major reason for irrigation, since farmers need a back-up water supply. It is a factor.
• B. High rainfall: Plenty of rain already supplies crops with enough water, so irrigation is largely unnecessary. It is NOT a factor encouraging irrigation.
• C. Need for more food: Irrigation raises output and permits more than one harvest per year. It is a factor.
• D. Presence of fertile soil: Fertile land gives good returns when water is added. It is a factor.

Step 4: Answer The "except" option is B. high rainfall.

Tip: In "all except" questions, first decide what the topic is for (irrigation = solving a water shortage), then pick the option that works against it. High rainfall is the opposite of a water shortage. Also, always underline the word "except" so you do not pick a correct factor by mistake.