Why are chemical fertilisers preferred to manure?
Chemical fertilisers are nutrient specific i.e. they can provide specifically nitrogen, potassium or phosphorus to the soil, as desired A manure on the other hand is not very rich in these plant nutrients.
Chemical fertilisers are water soluble so the plant can easily absorb them. Also they are easy to store, transport and apply to the crops. Manure does not have these qualities and that is why chemical fertilisers are preferred to manure.