Lesson Note

Subject: Agricultural science

Topic: Irrigation

Learning Objectives: By the end of the lesson, the learners should be able to:

  1. Define the term irrigation,
  2. State the importance of irrigation,
  3. Identify factors to be considered when making choice for irrigation methods,
  4. State the sources of water for irrigation.

Lesson Discussions

Definition Of Irrigation

Irrigation may be defined as the artificial application of water to the soil for farming purposes in order to supplement shortfall in rainfall.

Importance Of Irrigation

In agriculture, irrigation plays the following important roles:

  1. As rain begin late in some years, irrigation makes early planting possible.
  2. Irrigation ensures efficiency in crop production, resulting in increased crop production and income to the farmers.
  3. Irrigation serves as an insurance against drought since it tends to counter the undesirable effects of such dry weather conditions by providing optimum moisture for the soil during drought.
  4. Irrigation provides suitable environment for production of crop plants.
  5. It makes movement of plant nutrients and their absorption possible all the season, including dry season. For instance, a surface application of nitrogenous fertilizer will have no effect on a completely dry soil. There must be water to dissolve it and take it down to the roots. Should rain doesn’t make this happen, irrigation can.
  6. In places of salinity, irrigation can be used to leach undesirable salts from the soil.
  7. Irrigation makes it possible for farmers to raise a large variety of crops.
  8. Irrigation positively changes both plant and soil climate for the better.
  9. It may be used to soften tillage pans.

Choice Of Irrigation Method

  1. Water Supply: If the source of water supply is higher than the land to be irrigated, surface irrigation will probably be easiest. If water has to be pumped up, then sprinkler will be better.
  2. Soil: Factors to be considered here are topography and soil type. For instance, any method can be adopted if the slope is nearly level. If the slope is gentle, then furrow or border irrigation will be the best method. Steeper slope requires sprinkler. Soil with night water holding capacity requires surface application with large amount applied infrequently. If water holding capacity is low, however, more frequent application of small amounts of water is required and hence sprinkler system will be preferred.
  3. Crop: The system of irrigation adopted will depend on the types of crops grown and rooting habit. For instance, sprinkler irrigation is best for shallow rooting crops. For row crops and orchards, furrows are best. Then for forage crops, borders are more suitable.
  4. Climatic Factors: Sprinkler irrigation are unsuitable where strong winds are probable.
  5. Frequency Of Application: If frequent light watering is required, then sprinkler is the best.
  6. Economic Factors: The availability of capital will determine the system or method to adopt.

Sources Of Water For Irrigation

Water for irrigation may come from one or more of the following sources:

  1. Rivers
  2. Lakes
  3. Boreholes
  4. Wells
  5. Reservoir
  6. Irrigation dams
  7. Excavation pits
  8. Ponds
  9. Perennial streams

Done studying? See all previous lessons in Agriculture.

Take a quick test for this lesson

  1. What is irrigation?
  2. State the importance of irrigation.
  3. State and explain the factors to consider while making choice for irrigation method.
  4. Mention nine sources of water for irrigation

Questions answered correctly? Bravo!!

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