Soil

1. Soil

2. What is soil? • Soil is the part of the regolith that supports plant life • The regolith is the layer of rock and mineral fragments • Is found in all forms and places all over the world • It's sand on the ocean floor, mud in swamps, and dirt in forested and rural areas.

3. What is in “good soil”? • Good soil is composed of four different materials: mineral matter (45%), water (25 %), air (25 %), and organic matter/humus (5 %) • Water and air are found in the pore spaces in the soil • Humus (organic matter) comes from dead and decaying plants and animals • Soil water provides moisture and nutrients that sustain life

4. Soil Formation • There are five main factors that determine a soil’s characteristics: climate, parent material, time, organisms, and slope • Parent material is the source of all mineral matter in soils • The longer the soil has to form, the thicker the soil will become. • Climate has the greatest impact on soil formation because it impacts rates of weathering. • The nutrients within the soil come from organisms. Without this the foods would not be able to sustain life. • Slope will impact how thick or thin the soil layer is.

5. What occurs where? • Soil is broken up into different layers or horizons due to different composition • Horizon A • Topsoil, Composed of organic material; Plants and animals can be found here • Horizon B • Subsoil; Clay is the major component of this layer (hardpan); This is where you will most likely find the water table • Horizon C • Partially weathered rock; Deepest tree roots can be found here • Unweatherered Parent Material (UPM) • This layer is also known as the crust; There will be no roots found here

6. Soil Texture • Soil texture refers to the proportions of the different particle sizes that are found in soils • Categories are based on the percentages of sand, silt, and clay • The soil triangle is a diagram that categorizes soil by texture