What is soil?
Soils are the loose mineral or organic materials found on the earth's surface, usually (or averagely) made up of about 25% air, 25% water, 45% mineral and 5% organic matter (humus, tiny living organisms and sometimes plant residue).
It is the stuff that supports rooted plants in a natural environment. There are soils practically on every land that is not covered by water.
There are many types of soils, usually placed in classes (types) based on their color, profile, texture, composition or structure. Each soil type is formed differently and can be found in specific places on the earth’s immediate surface, mid and deep under the surface. Soils on the surface (a few millimeters deep) are usually exposed to direct climatic and environmental factors, and are easily blown away by wind, washed away by water or even broken down by temperature changes, human and animal activity. There are also soils found deep down the earth, often protected from climatic and environmental factors. (see more under soil profile)
Because soils are formed from a variety of ways and in infinite conditions, it is hard to give a number for the types of soils we have on earth. However, they can be grouped using the stuff that they are made of.
For this lesson, we shall look at Sandy, Silty, Clay, Loamy, Peaty and Chalky Soils.
One important subject that many farmers and soils scientists look out for is soil chemistry. This includes soil pH (the acidity of the soil), nutrient level, its organic content and the chemical composition of the minerals found in it. This is partly because different soils are used for different things and it is important to know something about the soils you choose. These are usually determined by the geographic location of the soils, the types of plants growing in them, and even the environmental factors (water and air) that the soil is exposed to.
The study of soils as naturally occurring phenomena is called pedology, and a person who studies soils (soil scientist) is called a pedologist.