Soil is made up of three main components – minerals that come from rocks below or nearby, organic matter which is the remains of plants and animals that use the soil, and the living organisms that reside in the soil. There are three ways in which soil is formed- mechanical, chemical, and biological weathering. Water is one of the most powerful causes of physical weathering because rocks are worn away as water flows over them.
Chemical weathering is the decomposition of rock which is the result of chemical reactions between minerals in the rock and the environment. On the other hand, biological weathering describes any processes of disintegration or decomposition accomplished by living organisms. For example, when a plant’s roots grow into cracks in rocks and create large crevices, biological weathering has occurred. Soil is organized in layers and typically begins with the weathering of bedrock to produce very fine particles and ends with a soil layer resting on bedrock. Characteristics of soil such as chemical features- pH, ion content, and ion-holding capacity- and physical factors- qualities of soil particles and bedrock- ultimately determine its suitability.
This factors determine how well a particular soil can supply essential minerals to plants and filter ions out of wastewater. Soils have a layered structure and have horizons with capital letters A, E, B, C, and O which can affect the location’s climate. Soil texture is determined by the ratio of sand, silt, and clay in the sample. These primary soil particles are arranged into secondary units called peds. The shape of these peds and the way in which they aggregate in the soil is known as soil structure. Soil structure affects how easily air, water, and plant roots move through soil. Soil consistence refers to the degree to which soil resists pressure. Terms such as loose, friable, sticky, nonsticky, plastic, nonplastic, soft, firm, and hard may be used to describe a soil’s consistency.
The bulk density (BD) expresses how much a soil weighs per unit volume. It depends on both the amount of pore space in a particular soil and the density of the soil particles. If a soil is subjected to pressure, pore spaces can collapse, decreasing total pore space. Compaction reduces the permeability of soil to water and air.
Surface erosion by water is influenced by the slope of the land- what determines whether a piece of land should be planted with grass, trees, or cultivated crops. One of the most obvious signs of erosion is the presence of gullies. In this experiment, the soil texture triangle (see picture below) was used to determine what type of soil a group received. Then in the next activity, the “Texture by Feel Analysis of Soil” was used to determine the texture of the unknown soil sample. And lastly, the soil profiles of three habitats- desert, prairie, and temperate rainforest- were tested to determine soil organization within the different soil horizons