Lesson Notes By Weeks and Term v4 - SHS 3

Lesson Video

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Performance objectives

• Identify and describe the different types of soil water.
• Explain the importance of soil water in agricultural production.

Lesson summary

*Analogy:* *Think of pouring water into a bucket filled with large stones. The water quickly runs through the large gaps and drains out the bottom. That's gravitational water.* B. Capillary Water Definition: This is the water held in the small pore spaces (called micropores) of the soil. It is held against the force of gravity by two forces: Cohesion: The attraction of water molecules to each other. Adhesion: The attraction of water molecules to the surface of soil particles. Characteristics: It can move in any direction in the soil (up, down, sideways) from wetter areas to drier areas. It is held with enough force to resist gravity, but not so tightly that plant roots cannot absorb it.

Lesson notes

*Analogy:* *Think of pouring water into a bucket filled with large stones. The water quickly runs through the large gaps and drains out the bottom. That's gravitational water.* B. Capillary Water Definition: This is the water held in the small pore spaces (called micropores) of the soil. It is held against the force of gravity by two forces: Cohesion: The attraction of water molecules to each other. Adhesion: The attraction of water molecules to the surface of soil particles. Characteristics: It can move in any direction in the soil (up, down, sideways) from wetter areas to drier areas. It is held with enough force to resist gravity, but not so tightly that plant roots cannot absorb it. Availability to Plants: This is the most important and the main source of available water for plants. Plant roots have enough suction power to pull this water from the soil particles. Importance in Agriculture: Photosynthesis: It is the primary source of water for this vital food-making process. Nutrient Transport: It acts as a solvent, dissolving soil minerals and transporting them from the soil into the plant through the roots. Turgidity: It keeps plant cells turgid (firm), providing support to stems and leaves. A lack of capillary water causes plants to wilt. Seed Germination: Seeds require capillary water to swell, break their dormancy, and germinate. Regulates Soil Temperature: It helps to buffer soil against extreme temperature changes.

*Analogy:* *Think of a sponge. When you dip it in water and lift it out, it doesn't drain completely. It holds a significant amount of water in its small pores. That's capillary water, ready to be squeezed out (or absorbed by roots).* C. Hygroscopic Water Definition: This is the water that forms a very thin film around individual soil particles. It is held extremely tightly by the forces of adhesion. Characteristics: It is held with such great force (a tension of more than 31 atmospheres) that it is immobile and does not move. It is the last bit of water remaining in the soil after it appears to be completely dry ("air-dry"). Availability to Plants: Hygroscopic water is completely unavailable to plants. The force holding it to the soil particle is much stronger than the suction force of the plant's roots. Importance: It has no direct agricultural importance for plant growth, but its presence indicates that the soil has reached a point of extreme dryness where plants can no longer survive.

*Analogy:* *Think of a dusty blackboard that you wipe with a wet cloth. Even after it looks dry, there is still a thin, invisible film of moisture stuck to the board. You can't get a drop of water from it. That's hygroscopic water.*

Key Soil Moisture Concepts

Evaluation guide

• Describe the types of so il water and their importance in Agricultural
• production.
• Think -pair-share: Learners in pairs brainstorm to come up with the types of soil
• water.