Runoff

Purpose
To demonstrate how rain affects topsoil.

Materials

Dirt

Red powdered tempera paint

Measuring spoon, teaspoon (5 ml)

Funnel

Coffee filter paper

Wide mouthed jar, 1 qt. (1 liter)

Measuring cup, 1 cup (250 ml)

Stirring spoon

Procedure

Add 1¼ teaspoon (1.25 ml) of red tempera paint to 114 cup (75 ml) of dirt. Mix thoroughly.

Set the funnel in the jar.

Place the coffee filter inside the funnel.

Pour the colored sand into the paper filter.

Add 1¼ (75 ml) of water to the funnel.

Observe the water dripping into the jar.

Pour this water out of the jar and add another 1¼ cup (75 ml) of water to the funnel.

Results
The liquid dripping out of the funnel is red.

Why?
The red paint represents nutrients in topsoil that are soluble in water. Nutrients dissolve in rainwater and feed the plants growing in the soil. If the rain is too heavy, the water runs across the land, taking the dissolved nutrients with it. Excessive rains can leave the topsoil lacking in necessary nutrients.

Printed with permission from Michal L. Le Vasseur, 2001

Download:
Runoff (Adobe PDF document)

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