What Components Make Up Soil?

Soil consists of minerals, organic matter, water, and air. Minerals from weathering rocks combined with decaying organic matter are what create the solid portion of soil. Space exists between these solid particles, and that space becomes filled with water and air. Healthy soil supports the lives of plants by supplying them with much needed nutrients, air, water, and support. It also supports the lives of all sorts of living organisms from microscopic bacteria to earthworms and insects.

The spaces between solid particles are called pores. Spaces greater than .03mm in diameter are referred to as macropores. These macropores are where roots grow, and they allow the flow of air and water within the soil. Micropores are those spaces less than 0.03mm in diameter, and they capture water.

Ideally, soil should consist of roughly equal parts of solid matter and pore space. Generally, about half of the pore space contains water and the other half contains air. When plants are watered or it rains, the water displaces the air previously occupying portions of the pore space. As the water drains or evaporates, air returns to fill the void between the solid particles. The solid portion of the soil is comprised primarily of minerals (roughly 90% or so of the solid material) and the remaining portion is made of organic material.