No one nutrient is  any more or less important than any other, they are just required by the plant or animal in different quantities.

Liebig's law of the minimum states that yield is proportional to the amount of the most limiting nutrient, whichever nutrient it may be. If the deficient nutrient is supplied, yields may be improved such that another nutrient becomes yield limiting.

For example, a plant may only require 1 unit of boron in comparison to 1,000,000 units of nitrogen, but without the single unit of boron, the plant will be unable to grow successfully, irrespective of how much nitrogen is applied.