Introduction

• Soil colloids are tiny particles in the soil that play a crucial role in soil chemistry, nutrient availability, and overall soil fertility.

What are Soil Colloids?

• The word colloid comes from the Greek word “kolla,” which means “glue-like.”
• Soil colloids are very small particles that remain suspended in water, forming a gel-like consistency.
• They are part of the clay fraction of the soil, with particles smaller than 0.002 mm in size.
• Particles smaller than 0.001 mm are known as soil colloids and are key in many soil processes.

Characteristics of Soil Colloids

a. Size:

• Soil colloids are particles smaller than 0.001 mm in diameter.

b. Insolubility in Water:

• They do not dissolve in water but remain suspended.

c. Suspension in Water:

• Soil colloids do not settle like larger particles; they stay suspended in water due to their small size and surface charges.

Types of Soil Colloids

Soil colloids can be organic or mineral in nature:

a. Organic Colloids:

• Derived from decaying plant and animal matter.
• Commonly known as humus, which has high cation exchange capacity (CEC) and helps with nutrient retention.

b. Mineral Colloids:

• Primarily clay particles that are small in size and have a significant impact on soil properties, like texture and structure.
• Clay minerals such as kaolinite, montmorillonite, and illite are common examples.