1 Soil Color & Its Causes

2 Factors that give soil color 1.Organic matter 2.Weathered mineral material composing the soil 3.Quantity and condition of iron present

3 Dark Color in the A Horizon Usually indicates the presence of organic matter This is a characteristic of the A horizon

4 Sub-soil Color Determination Quantity and condition of iron Red colors = usually associated with unhydrated iron oxides and indicate a well drained soil Yellow colors = largely due to hydrated iron oxides and generally indicate a somewhat more moist condition than red colors

5 Basic Color Classifications Light Medium Dark

6 Color Determination in the field ALWAYS USE MOIST SOIL Munsell’s color charts Absolute black = 0 Absolute white = 10 Light soils hue value = 7 or more Medium soils hue value = 5 – 6 Dark soils hue value = 4 or less

7 Munsell Color Charts Hue = dominant spectral or “rainbow” color Red, Yellow, Blue, Green Value = relative blackness or whiteness Reflected light Chroma = purity of “color” Number increases and the color is more brilliant as grayness decreases

8 Change in soil color… Indicates a difference in the soil’s mineral origin (parent material) Or change in soil development

9 Mottles Spots of different colors in the soil Generally indicate that the soil has periods of inadequate aeration each year Usually rust colored Bluish, grayish, & greenish subsoils (gleying) – with or w/o mottles = indicate longer periods each year of waterlogged conditions & inadequate aeration.