Which is absent in plant ash?

Solution(By Examveda Team)

Nitrogen is absent in plant ash.
Plant ash is the residue left behind when plants are heated to high temperatures. The fresh weight of the plant includes the weight of water and protoplasm. Plant ash acts like a time-release fertilizer under natural conditions of moistening and drying, freezing and thawing.
Wood ash contains nutrients that can be beneficial for plant growth. Calcium is the plant nutrient most commonly found in wood ash and may comprise 20% or more of its content, but it lacks nitrogen.