Soil may look the same wherever you go, but if you look closely you will notice that the color and texture can be very different. In this activity, we are going to investigate these differences by getting our hands into the soil and attempt to categorize the soil into different types. This will help us to get a better understanding of the different components of soil and why a specific type may be so important to a particular habitat. This will also introduce how engineered soils are constructed. This activity can be done at home but is optimal in a group setting.
Engineered soils are made from specific ratios of sand, silt, clay, and organic components like compost or leaves. Engineered soils increase the permeation of runoff and reduce pollution through natural filtering. This is a form of stormwater management used along highways, parking lots, rooftops, and other low-impact designs. The benefits of engineered soils are that they can hold water, reduce flooding, and filter out nutrients from runoff, recycling metals and chemicals useful for plants back into the environment. To remain in place, soils need the help of plant roots to prevent erosion.
Show students a short video or demonstration of a texture test. Ask them to describe differences in color and texture of soils they may have noticed near their home, around the school, or at the playground. Ask about why these differences may be important and what color may tell us about soil.
The four major components of soil are inorganic minerals, organic matter, water, and air.
Sandy soil is light, warm, and dry, and tends to be acidic and low in nutrients. Sandy soils are often known as light soils because they have a high proportion of sand and relatively little clay. Clay weighs more than sand.
Sandy soils drain water quickly and are easy to work with. They are quicker to warm up in spring than clay soils but tend to dry out in summer. Sandy soils may suffer from low nutrients becuase organic matter is washed away by rain.
The addition of organic matter can help give plants an additional boost of nutrients by improving the nutrient and water-holding capacity of the soil.
Clay soil is a heavy soil type that benefits from high nutrients. Clay soils remain wet and cold in winter but dry out in summer. These soils are made of over 25 percent clay, and because of the spaces found between clay particles, clay soils hold a high amount of water. Since these soils drain slowly and take longer to warm up in spring, and because they may dry and crack in summer, they can often challenge gardeners.
Silt soil is a light and moisture-retentive soil type with a high fertility rating. As silt soils are comprised of medium sized particles, they drain and hold moisture well.
As the particles are fine, they can be easily compacted, prone to washing away with rain. By adding organic matter, the silt particles can be bound into more stable clumps.
Loam soil is a sand, silt and clay rich soil with a balance of organic matter.
These soils are fertile, easy to work with and provide good drainage. Depending on their predominant composition, they can be either sandy loam or clay loam.
Because loam soils have a balanced mix of soil particles, they are considered to be a gardener's best friend, but they still may benefit from a topping of additional organic matter.
