Plants uptake essential elements from the soil through their roots and from the air through their leaves.  Some elements are directly involved in plant metabolism, However, this doesnt  account for the so-called beneficial elements which arent required, but have clear positive effects on plant growth. These include N =Nitrogen,P = Phosphorus,K = Potassium, Ca =Calcium Mg =Magnesium.

Advanced Nutrients	Atami Bcuzz
Biobizz Products	Canna Products
Growth Technology Products	House and Garden Products
Other Nutrients	Plagron Products