Next to the texture and the structure, we also thought to quickly look into pH and soil color. pH is an indicator of the degree of acidity, which is important when interpreting soil surveys for fertility purposes, and soil color is an indicator for possible inferences on parent material, organic carbon content, and the degree of wetness or drainage condition.

Soil color: Soil color is described by using Munsell soil color charts. A color notion (e.g., 10YR 4/5) is composed of three components namely hue (relation to red, yellow and blue), value (lightness or darkness) and chroma (paleness or strength).

For more explanation, see also The Color of Soil

Figure 8.1: Determine Soil Color (the person with the color charts in the hand stands back to the sun)

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Soil Color

Soil color is used to infer ‘source of parent material' (making use of the‘HUE'), ‘organic matter content' (making use of ‘VALUE'), and the ‘wetness (drainage) condition' (making use of ‘CHROMA'). Different hues may mean different parent materials; darker values may mean presence or absence of organic matter; low chroma indicates wetness (hydromorphism).

pH determination:

Although chemical analyses are done in laboratory, and on the soil samples collected from the representative (orthotype) soil profile, it is customary that pH (degree of acidity) and EC (electrical conductivity) are measured in field using simple (field) kits. Here, pH determination is shown in a short film, where Hellige Kit (colorometric technique) is used. Lower pH (than 6-7) is acid, and higher values mean basic. pH (KCl) is often used to infer a very important soil property (base saturation percent, calculated using sum of bases and CEC; a tedious laboratory analysis). For further details, see Pedosphere and Its Dynamics Book Series (pages 173-175)

The Figure 8.2 below depicts the sand ruler and the pH meter used in the field.

Figure 8.2: Sand Ruler (used to determine sands'size) and pH (degree of acidity) Meter

 

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Using pH Meter