Soil color is an indicator of its chemical composition and a very good reference for its fertility assessment.
Soil classification by fertility
The dark soils reflect a high nutrient background. They are ideal for most cultures and their value increases as the digging depth is higher.
Then the fertility decreases from black soils to brown ones (rust, red, gray, yellow). Whitish soils are the least fertile so they are less recommended for agriculture.
Also, black soils absorb more solar radiation during the day and release more heat during the night, leading to the formation of an “underground dew”, a phenomenon particularly favorable to plants.
Other interesting things about soils
The chromatic appearance of the soil horizons provides much information about how “plants feel”. For example:
The mosaic marbled appearance of the soil layers suggests a temporary excess of water or that the groundwater is fluctuating.
The bluish-green or olive color indicates the presence of ferrous compounds in the soil of your garden. These are formed in the absence oxygen, which makes the soil unsuitable for plants.
The existence of light halos around the roots indicates an excessive soil wetting, which usually leads to drying of the trees.
Good to know
Complete data on the composition and suitability of a soil for a particular crop are obtained only by specific laboratory analyzes.