United States Department of Agriculture
Natural Resources Conservation Service		 North Carolina Go to Accessibility Information
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Apple Lesson

S.K. Worm asks "How much topsoil do we have to use?"

Objective

Students will comprehend that the earth and all of its resources are limited.

Background

Protecting our soil is very important. We need soil to grow food. Advances technology has enabled the world to feed many of its people, but the world's population continues to expand. A fixed land resource base and an ever-increasing population to feed puts a greater need on soil conservation.

Materials

One large apple, sharp knife, and cutting board

Procedures
  1. Consider this apple represents the earth. Slice the apple into quarters, and set three quarters aside.
  2. The three quarters represent the oceans on the earth (75% of the earth is water).
  3. One quarter represents the earth's land area. Slice this quarter in half and set aside one piece.
  4. One eighth represents the land area that is inhospitable for humans (polar areas, deserts, high mountains).
  5. One eighth represents the land areas where people live, but not necessarily where they grow food that's needed for life.
  6. Slice the 1/8 into four sections. (1) One of these (1/16) represents the areas where we cannot grow food--either the soil is too poor, the slope is too steep, the soil is too wet, or temperatures are too cold. (2) Another section represents the land areas that are covered with concrete or pavement (cities, parking lots, highways, and interstates). (3) Another section represents areas where people live (cities, houses, condominiums, and apartments).
  7. The remaining section represents the land area of the earth where it is conducive to grow food. Peel the 1/32 slice of the earth. This tiny bit of peel represents the very thin surface of the earth's crust where humans depend upon the rich topsoil to grow food for the entire world population.
Evaluation

Our planet is finite. We do not realize how important our soil resource is. It takes 300-500 years to form one inch of valuable topsoil. This same inch could be washed away overnight in a rainstorm. What can you do to prevent soil erosion and protect our world's land resources?

An apple being sliced in small peices to demonstrate the limited land humankind has to live and produce food on.

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