Vermicompost biofertilizer is rich in which mineral nutrient?

• A biofertilizer is any naturally occurring agent that increases the fertility and yielding capacity of the soil. 
• Vermiculture is the rearing and usage of worms for the process of decomposition. Vermicompost is the final product that is made by the decomposition process carried out by worms. 
• Earthworms are known to increase the fertility of the soil. Hence, they are considered biofertilizers. 
• They break down the organic matter present in soil and increase the amount of water-soluble nutrients in the soil as well.

Hence, the correct option is D.