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Letís take a closer look at the top horizon.  You could also call this the surface horizon, or the A horizon.  It is dark in color.  Do you know why?  Because organic matter has been added to the soil.  picture shows the soil in dark brown color meaning that the soil has been added some organic matter Organic matter comes from the plant roots, leaves, and other material as it breaks down and decomposes in the soil.  Microorganisms use this organic matter for food.  Do you see below the second nail, the soil looks lighter?  Do you know why? There isnít as much organic matter down there.


Now, looking at the very bottom soil horizon.  What do you notice now?  This horizon is called a B horizon, because itís below the A horizon.  It has a much different color than the A horizon. shows the soil in red color meaning that it has a lot of iron Does it remind you of rusty metal?  The B horizon of this soil profile contains a lot of iron, which makes the soil look so red.


How do soil scientists describe the many different soil colors?  By using a Munsell Color Book.  What you do is match a piece of your soil to a colored square in the book.  shows the Munsel color book with some soil samples

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