What is Soil? A Definition

Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support the life of plants and other soil organisms.

Some scientific definitions distinguish dirt from soil by restricting the former term specifically to displaced soil (see below).

Soil is a three-state system that consists of a solid phase of minerals and organic matter (the soil matrix), as well as a porous phase that holds gases (the soil atmosphere) and water (the soil solution).

Soil Profile

What is Soil?

Soil is a product of several factors: the influence of climate, relief (elevation, orientation, and terrain slope), organisms, and the soil’s parent materials (original minerals) interacting over time.

Soil is essential for life as we know it on Earth. It provides a home for plants and animals and helps regulate the Earth’s climate by carbon sequestering. Soil also stores water and nutrients, which are essential for plant growth.

Soil does more than store water. It also filters particulates and other harmful elements before being released into waterways and wells. The chemical composition of the soil can also affect water quality for the good and bad.

Soil creation or a better term may be soil development is a slow process and thus soil should be considered a non-renewable resource.

Soil erosion is a significant problem, and it can be caused by various factors, including deforestation, overgrazing, and agricultural practices.

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we are losing soil

There are several things that can be done to protect soil, including:

  • Planting trees and shrubs
  • Grazing animals in a rotational system
  • Using conservation tillage practices
  • Avoiding the use of pesticides and herbicides
  • Managing manure and other organic wastes properly

Here are some books that discuss how the soil/agriculture system should work. These books should be considered Must Reads.

Here are some additional facts about soil:

  • The average soil depth is about 10 inches but can range from a few inches to several feet.
  • A teaspoon of healthy soil is home to millions of organisms, including bacteria, fungi, algae, protozoa, and earthworms.
  • Soil is a significant carbon storehouse, containing about twice as much carbon as the atmosphere.
soil has life in it

Why Soil Should Never Be Called Dirt

Soil and dirt are often used interchangeably, but they are not the same thing. Soil is a living, dynamic system that supports life, while dirt is simply a mixture of mineral particles and organic matter.

As mentioned previously, it doesn’t hurt to review soil is made up of four main components:

  • Organic matter is the living and decaying matter that gives soil its dark color and texture. Organic matter is vital for soil health because it provides nutrients for plants, helps to retain water, and improves soil structure.
  • Minerals: These are the inorganic particles that make up the bulk of soil. Minerals provide nutrients for plants and help give soil strength and structure.
  • Water: Water is essential for plant growth and soil health. Soil can hold a large amount of water, which helps to regulate the Earth’s climate and provide water for plants during dry periods.
  • Air: Air is essential for the growth of soil organisms. Soil organisms help to break down organic matter and release nutrients for plants.

Dirt, on the other hand, is simply a mixture of mineral particles and organic matter. It does not contain the same level of organic matter as soil, and it does not support the same level of biological activity.

Dirt is also more likely to be compacted, which can make it difficult for water and air to move through it.

The difference between soil and dirt is a key thing to remember because soil is essential for life on Earth. It provides a home for plants and animals, and it helps to regulate the Earth’s climate.

Dirt, on the other hand, is not as valuable as soil. It can be used for construction and other purposes, but it does not have the same benefits as soil.

Quote to Remember – I Say This All the Time

Don’t call soil dirt. You grow plants in soil. What you sweep up off the floor is dirt.

Stock images by Depositphotos


  • Todd

    Todd is the founder of Home Microgreens & the Home Microgreens store. He also writes for several other websites, including MyViewFromTheWoods.com. Todd worked at a large farm market, garden & nursery center for 20 years. Somehow he snuck off to become a geologist and professor before coming back to his senses to write & lecture about microgreens and gardening. When not at the computer, he can be found in the garden, trout stream, or mountain trail with his new Springer Spaniel Caden.

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