Phosphorus is critical for photosynthesis and growth. If you find your plants are slow-growing or notice the foliage changing from a vibrant green to purplish-red or blue, a phosphorus deficiency may be the problem.
Plants need nitrogen for the same reason that humans need nitrogen: to form amino acids. Amino acids are nitrogen-containing compounds that make up proteins.
In order to understand fulvic acid, we need to revisit our elementary school science curriculum for a quick refresher on soil, that dark and magical substance from whence all life springs.