05/07/2017
The Science of Soil
What is soil?
Soil is loose upper part of the Earth’s surface where plants grow. Soil consists of a mix organic material (decayed plants and animals) and broken bits of rocks and minerals.
Soils are complex mixtures of minerals, water, air organic matter and countless organisms that are decaying remains of once living things. It forms at the surface of land – it is the skin of the earth. Soil is capable of supporting plant life and is vital to life on earth.
It also contains lot of tiny creatures, such as earthworms. Earthworms turn the plant and animal material into nutrients. They also dig through the soil, which lightens and loosens it so plants grow better.
How is soil formed?
Soil is formed over a long period of time by a number of factors. It can take up to 1000 years for just an inch of soil to form. Besides time, another factor that helps soil include:
Living organisms – This includes organisms such as plants, fungi, animals and bacteria.
Topography – This is the relief or slope of the surface of land where the soil is forming.
Climate – The overall climate and weather where the soil is forming.
Parent material – The parent material is the minerals and rocks that are slowly disintegrating to form the soil.
Why is soil important?
At first you may think of soil as just dirt. Something you want to get rid of. However, soil plays a very important role in supporting life on earth.
Plants – Many plants need soil to grow. Plants use soil not only for nutrients, but also as a way to anchor themselves into the ground using their roots.
Atmosphere – Soil impacts our atmosphere releasing gases such as Oxygen, carbon dioxide into the air.
Living organism - Many animals, fungi and bacteria rely on soil as a place to live.
Nutrient cycles – The soil plays an important role in cycling nutrients including the carbon and nitrogen cycles.
Water – The soil helps to filter and clean our water.
So then, what is dirt?
Dirt is what gets on our cloths or under our fingernails. It is soil that is out of place in our world – weather tracked inside by shoes or on our cloths. Dirt is also soil that has lost the characteristics that give the ability to support life – it is dead.
Properties of Soil
Soil is often described using several characteristics including texture, structure, density, temperature, colour consistency and porosity. One of the most important properties of soil is the texture. Texture is the measure of whether is more like san, silt or clay. The more like sand a soil is the less water it can hold. On the other hand, the more like clay a soil is the more water it can hold.
Soil Horizons
Soil is made up of many layers. These layers are often called horizons. Depending on the type of soil there may be several layers. There are three main horizons, which are present in the soil.
Organic – The layer (also called the humus layer) is thick layer of plant remains such as leaves and twigs.
Topsoil – Topsoil is considered the top horizon. It is fairly thin layer (5 to 10 inches thick composed of organic matter and minerals. This layer is the primary layer where plants and organisms live.
Subsoil – Subsoil is considered the second horizon. This layer is made primarily of clay, iron and organic matter, which accumulated through a process called illuviation.
Parent material – The parent material is considered the third horizon. This layer is called the parent material because the upper layers developed from this layer. It is made up mostly of large rocks.
Bedrock – The bottom layer is several feet below the surface. The bedrock is made up of solid mass of rock
Type of soil
There are six types of soils such as Sandy, Silty, Clay, Peaty, Saline and Loam.
The type of soil that gardens and gardeners’ love is lomy soil. It contains a balance of all three soil materials – silt, sand and clay – plus humus. It has the higher pH and calcium levels because of its previous organic matter content. Loam is dark in colour and is mealy soft, dry and crumbly in your hands. It has tight hold on water and plant food but it drains well and air moves freely between soil particles down to roots. The feel test for loam yields a smooth, partly gritty, partly sticky ball that crumbles easily.
