Initial Publication Date: January 13, 2021

Introduction: Know Soil, Know Life

Chapter Summary

Soil is the foundation our natural living world depends on. It is the often-unappreciated substance of life, the dynamic material that civilization is built on, the critical-zone of the earth. Most of our food, much of our clothing (fiber), and building materials (wood, clay, bricks, etc.) are derived directly or indirectly from soils or the plants grown on soils. Soils are also a key component of the filtration of surface water before it becomes groundwater.

Not all soils are created equal. Although all soils are formed by similar processes (additions, losses, transformations, and translocations) they are nonetheless diverse and dynamic. This diversity is based on the conditions and environment (factors of formation) in which they have developed or formed. Soils, therefore, need to be managed appropriately to maintain their ecosystem services.

Soils will increasingly be looked upon to provide basic resources as the population continues to rise. It is imperative that we understand soils in order to responsibly conserve and manage this non-renewable resource. It may take hundreds of years for a few centimeters of soil to form however if poorly managed those few centimeters can disappear overnight.

Educator Background

Soil and its components

What exactly IS soil? First and foremost, the soil is not dirt. Dirt is the stuff under your fingernails; it is the stuff you sweep up off the floor; it is unwanted and unnecessary. Soil, on the other hand, is essential for life as we know it; so, soil cannot be dirt. Dirt may be soil out of place, just as a weed is a plant out of place. For example, a rose in a cornfield, while beautiful, is a weed and a corn plant in a rose garden is also a weed. So, when you track mud (wet soil) inside you are putting the soil in a place it is not wanted. At that point, it becomes dirt.

This does not tell us what soil is but rather what it is not. There are several definitions of soil depending on who you ask. Perhaps the simplest is:
"Soil is a living, dynamic resource that is at the surface of our earth."

To take that definition a little further soil is defined as:
"A natural, three-dimensional body at the earth's surface. It is capable of supporting plants and has properties resulting from the effects of climate and living matter acting on earthy parent material, as conditioned by relief and by the passage of time."

Soil (pedosphere) occurs at the intersection of rocks (lithosphere), water (hydrosphere) air (atmosphere), and living organisms (biosphere). There are tens of thousands of different soils worldwide occurring on every continent and virtually anywhere where plant life can set its roots. An understanding of the environment requires an understanding of soil – what it is; how it is formed; what it is made of; and how it is used. Soils serve as a repository of many geological and climatic events of the location where it's located. It is a window to the past, but it can also serve as a view of the future as its properties relate to how we can and should use and manage this finite resource.


A handful of soil may at first seem lifeless and solid but, soils are teeming with life and contain pores that are full of air and water. There are 5 components to every soil – minerals, living organic matter (OM), dead organic matter, water, and air. The mineral, living OM, and dead OM make up the solid phase. The water and air make up the pore space. A typical handful of soil contains 50% pore space, 45-50% solids, and 0-5% OM.

Soils are critical to life (including people) on earth

Why is there life on earth? It may come as a surprise that all living things depend on four basic things. You may first think of food, shelter, and water. With a little more thought; air. Looking at the bigger picture, energy is seen as critical. The ultimate source of energy is sunlight with no sunlight the earth would. Upon further consideration, the first three items – food, fiber, and shelter – are all related to a single often overlooked and looked down upon item. This item is soil.