What is Soil?
Subtitle 1: Describing Soil
Soil is a complex mixture of minerals, organic matter, gases, liquids, and innumerable organisms that together support life on Earth. Depending on the soil scientists that you ask, there is no one definition of soil. The simplest definition of soil is as a natural body of relatively-unconsolidated material on the Earth’s surface that is composed of rock and mineral particles, organic material, air and water. Soil is part of the terrestrial environment and is the basis of terrestrial ecosystem functioning.

Soil is the product of the interaction of a variety of mostly weathering forces and processes. Soils are classified based on several characteristics, such as texture, color, mineralogy, structure, and organic matter content. Soil texture can be classified into sand, silt, and clay, and these particles are combined in different ratios to form a soil’s texture. Color is also a very important characteristic in soil classification, as it can give an indication of the type of minerals present and of certain soil processes, such as decomposition or oxidation.

On the microscopic level, soil is composed of mineral components, organic matter, and mesoelements, which are the components that hold the soil together. Mesoelements include clay particles and organic matter, which help bind the soil particles together and form the basis of soil structure. Soil also contains numerous species of living organisms, ranging in size from microscopic bacteria, to nematodes and earthworms, to larger insects and animals, such as ants and moles.

Subtitle 2: Formation of Soil
Soil is formed through a combination of weathering and erosion processes, with a key factor often being climate. Physical weathering is the physical breaking apart of rocks by wind, water, and temperature, which can occur due to erosional forces or repeated cycles of wetting and drying. Chemical weathering is the break down of rocks due to chemical reactions, such as leaching, oxidation, and acid-base reactions.

Biological weathering is a form of chemical weathering that is driven by living organisms, such as bacteria or fungi. This type of weathering can be extremely effective in weathering rocks because it can occur on a very small scale. The combination of these three processes leads to the formation of soil particles.

Soils also form through geochemical processes, such as the movement of elements, acids, and other compounds through the soil. This process is often referred to as “soil genesis” and it is the process by which soil particles form and then combine with organic matter, minerals, and other elements.

Subtitle 3: Soil Ecosystems
Soils are complex ecosystems that contain myriad living organisms and are vital to plant growth and health as well as the functioning of terrestrial ecosystems. These organisms range in size from microscopic bacteria and fungi, to larger animals such as earthworms, moles, and insects.

These organisms are important because they are vital to many of the primary processes that occur in soils, such as nutrient cycling, decomposition, and soil formation. Microorganisms are particularly important, as they are responsible for breaking down organic matter and releasing nutrients into the soil. Other organisms, such as earthworms, create tunnels which allow air and water to infiltrate the soil and improve drainage.

Conclusion
Soil is a complex mixture of minerals, organic matter, gases, liquids, and innumerable organisms that together support a wide variety of terrestrial ecosystems. Soil formation is driven by weathering and erosion processes and biological processes, and it is this complexity that makes soil such an indispensable part of terrestrial ecosystems. Without healthy soil, plants cannot grow and provide the essential ecosystem services that many organisms, including humans, rely on for their survival.