Notes

Texture: Soil may be smooth or rough depending on the size of the rock particles it contains. Larger particles like gravel and sand give soil a rough texture. Smaller particles like silt and clay give soil a smoother texture. Different soil samples have different combinations of particles sizes.

Sand is made up of relatively large particles, giving it a rougher texture.



Pore Space: The size of the particles that make up soil affects the amount of space between the particles. Smaller particles have smaller pore spaces, and larger particles have larger pore spaces. These differences can have a significant effect on plant growth. For example, too little pore space will limit water drainage. Loam, which has roughly equal amounts of the different particle sizes, drains well and is usually a good choice for growing plants.


There is very little space between the small particles on the left, while there is more space between the larger particles on the right.



Color: Soil color gives scientists clues about the soil’s composition. Dark soil is usually rich in humus. Red or orange soil may have high iron content. White soil may be rich in the mineral calcite. A grayish color may be a sign that soil is not draining well.