Other soil components

There are three other components that make up the soil. We must not forget the living organisms that inhabit the soil. These are so important that we have a special topic feature on them (The Living Soil). They are extremely important because of their numbers (billions in just a tea spoon full of soil), the fact that they break down the organic remains, the dying vegetation, deposited on and in soils, to release nutrients for the next generation of plants, and they also play a big part in creating the structure of soils.

All soils contain pores. These are vital for the movement of roots, water, air and organisms. All soils are composed of a mixture of particle sizes and these never fit together exactly. Always there will be pores between the particles and aggregates Soil in some senses is like a sponge containing numerous holes in which the water can sit and through which air can circulate. Pore space can vary from a few percent to over 40 percent of the volume of the soil.The final important part of the soil is the water that it contains. The soil acts as a reservoir for water and moderates the flow of water to lakes and rivers. The water that is held in the pores of the soil and around mineral grains is vital in sustaining plant growth and the living soil organisms. At times it can fill the pores making the soil waterlogged but often it will drain through the soil and the pores will be only partially filled. The water that occurs in the pores will contain various nutrients in solution and as plants take up water so they will take in nutrients which are a major source of food for the plants that grow in the soil. This balance between the soil mineral particles, organic matter, the living organisms in the soil, and the pores containing air and water is so important in maintaining the human population. It is important that all users of soils understand this relationship.