Question

Fertile agricultural soil appears deep coloured at the surface as compared to the colour one metre down. The reason for the colour of topsoil is due to:

• A. Organic matter
• B. Fertilizers
• C. Moisture
• D. Rocks

Answer 1

The correct option is A Organic matter

Topsoil contains leaves and organic matter which decompose to form the upper organic layer, known as humus. The reason for the colour of topsoil is due to the organic matter present in it. Sodium content influences the intensity of colour of organic matter and therefore the soil. Sodium causes the organic matter (humus) to disperse more readily and spread over the soil particles, making the soil look darker.