Question

Why is plasticity and cohesion play an important role in workablility of soil

Answer 1

Plasticity is a soil property which enables a moist soil to change shape 
on an applied force and retain this shape even when the force is withdrawn. Thus sandy soils are 
considered as non-plastic and clayey soils as plastic. Cohesion, on the other hand, is a property 
of the particles to stick to one another by cohesive force. Plastic soils are cohesive. Plasticity and 
cohesion reflect the soil consistency and workability of the soils. Black soils are highly plastic 
and highly cohesive making tillage operation difficult.