(a) With the aid of an annotated diagram only, illustrate the water cycle. (b) State three forms in which water exists in the soil (c) List five importance ...

Answer Details

(a) The water cycle (hydrological cycle)

The water cycle is the continuous circulation of water between the earth surface and the atmosphere. The annotated diagram should show the following labelled stages arranged in a cycle:

• Evaporation: heat from the sun turns water from seas, rivers and lakes into water vapour that rises into the atmosphere.
• Transpiration: plants give out water vapour from their leaves into the atmosphere.
• Condensation: the rising water vapour cools and condenses to form clouds.
• Precipitation: the condensed water falls back to the earth as rain, hail or dew.
• Run-off and infiltration: some water flows over the surface into rivers and seas, while some sinks into the soil to become ground water, and the cycle repeats.

(b) Three forms in which water exists in the soil

1. Gravitational water (free water that drains away by gravity).
2. Capillary water (held around soil particles and available to plants).
3. Hygroscopic water (tightly held as a thin film on soil particles, not available to plants).

(c) Five importance of water to crops

• It is needed for seed germination.
• It is a raw material for photosynthesis.
• It dissolves soil nutrients and aids their absorption and transport within the plant.
• It keeps plant cells turgid, maintaining the shape and firmness of the plant.
• It cools the plant through transpiration and regulates temperature.