Potassic fertiliser is graded based on its __________ content.

ANS:B - K₂O

Potassic fertilizer is graded based on its potassium oxide (K2O) content. Potassium oxide (K2O) is a measure of the potassium content in fertilizers. It represents the amount of potassium (K) available for plant uptake in the form of potassium ions (K⁺). Potassium is an essential nutrient for plant growth and is often included in fertilizers to improve crop yield and quality. So, the correct option is: K2O