Question

A fertile agricultural soil appears deep coloured at the surface as compared to soil one metre down. The reason for colour of top soil is

(a) more moisture

(b) rich in organic matter

(c) rich in iron, calcium and magnesium

(d) recent formation.

Answer 1

The answer is (b) rich in organic matter.

Explaination:

The soil color is mainly produced by the minerals present and by the organic matter content.

Dark brown and black color in soil indicates that the soil has a high organic matter content.

Wet soil will appear darker than dry soil because it holds more moisture content due to the presence of organic matter.

Organic matter tends to make soil color darker. Humus which is a final stage of the organic matter breakdown is black in color. Throughout the stages of organic matter breakdown, the color imparted to the soil varies from brown to black.

Sodium content of soil causes the organic matter to disperse more readily and spread over the soil particles making the soil llok darker or blacker.