Understanding the growth of land plants demands more than just the study of plants by themselves. There is an intimate interrelationship between the plants and the soil in which they are growing. At the crux of this interrelationship are root hairs, fine hairlike outgrows from the root’s surface cells. Show students the dense “fuzz” of root hairs on the root of a germinating seed (type into your browser: root hairs and soil images). Help them picture how these root hairs make intimate contact with virtually every soil particle and penetrate every space within a centimeter or so of the root. They are the part of the plant that does the real work of absorbing water and nutrients from the soil, and they also must absorb air (oxygen) for their own energy metabolism. (When you pull a plant and examine the roots, root hairs are not seen because they are so delicate that they are stripped off in the pulling.)
This “picture” should help students visualize the key requirements for soil.
It surface must be porous so the water will enter (infiltrate) and not run off the surface.
It must hold water (via capillary action) making it available to plants.
It must be loose enough to facilitate aeration.
Necessary nutrients (Nitrogen, phosphorous, potassium, etc.) must be present.
See the text for further explanations
Erosion (having soil carried away by water and wind) is the most serious cause of degradation of soil.
Type into your browser: erosion of crop lands images
The most effective erosion prevention practice is to keep a vegetative cover on the soil. The following video provides a demonstration of this. By visualizing the root hairs binding soil particles, kids readily see how this works.