Soil Composition, Types, and Conservation Methods
Soil Composition and Properties
Key Soil Components
- Soil: The loose, weathered material on Earth’s surface in which plants can grow.
- Humus: Dark-colored organic material in soil.
- Horizons: Layers of soil that differ in color and texture from the layers above or below it.
- Soil Profile: A vertical section of soil from the ground surface to the parent rock.
- Topsoil: The crumbly, topmost layer of soil made up of clay and other minerals and humus (nutrients and decaying plant and animal matter).
- Below: Subsoil, usually consisting of clay and other particles washed down from the topsoil, but little humus.
Soil Conservation Methods
- Windbreaks: A method of conservation that consists of planting trees to protect the soil from wind and strong rainfalls.
- Soil Erosion: The removal of the topsoil and its nutrients caused by agents of erosion such as wind.
- Clay: A type of soil with small particles; it is dense and soft.
- Parent Material: Found below the C horizon, it is the underlying geological material (generally bedrock or a superficial or drift deposit) in which soil horizons form. When parent material is weathered, mineral particles are formed.
- Transported Soil: Soil that was transported from one horizon to another due to agents of erosion.
- Horizon C: The horizon from the soil profile where weathered pieces of bedrock are usually found.
Soil Texture Analysis
- 50% silt, 9% clay, 41% sand: Silty Clay
- 30% sand, 60% silt, 10% clay: Sandy Clay Loam
- 20% clay, 35% sand, 45% silt: Loam
- Loam: The perfect soil for farming, where a huge variety of plants are able to grow. It is the only kind of soil that is not predominantly sand, silt, or clay.
- Sandy Clay Loam: A loam that features a large amount of sand, but also has a considerable amount of clay, and almost no silt. The contrast between the high amount of sand and clay indicates that this type of soil has good pore space, aeration, absorption, and drainage. This is because sand has the largest particle size and clay the smallest, so they complement each other, forming good soil for plants.
- Silty Clay: Light and moisture-retentive soils that are very fertile. As silt soils are comprised of medium-sized particles, they are well-drained and hold moisture well. As the particles are fine, they can be easily compacted and are prone to washing away with rain.
Soil Conservation Techniques
Soil is where plants grow. Some methods to conserve soil from leaching or soil erosion are:
- Terraces: When crops are on a slope, terraces are used to slow down the flow of water. These are paths that go down the slope so that water doesn’t damage crops.
- Windbreaks: Consist of making a hole where water from rainfall is stored, to protect the crop area from floods.
- Contour Plowing: Consists of making a hole where water from rainfall is stored, to protect the crop area from floods.
Soil Profiles in Different Biomes
Rainforest
The soil profile of the rainforest is similar to that of the taiga biome. In the first horizon, there’s a layer of humus that contains organic matter, often reddish due to iron oxide and other minerals mixed in, though in lower amounts, found in the B horizon. Finally, in the C horizon, there are pieces of rock that were weathered from the bedrock found below.
Taiga
The first horizon is composed of a black, thick layer of acid humus and few soil organisms. Then, Horizon A, which is the topsoil, becomes sandy as some materials are washed out. In the same horizon, we can find three small layers: one composed of redeposited organic matter, another of iron, and the last one of aluminum. Also, there is a lot of precipitation, which results in leaching of clays, organic matter, and oxides. In Horizon B (subsoil), there is an accumulation of clays stained by iron oxides. It transitions into a red or red-brown horizon. There is also a through-flow of soil water, leading to a loss of nutrients. In the last horizon, bedrock is formed because of the weathered material.