What Is The Acronym Ei Or El?

[spacewolf]

As title.
 
I often see the abbreviation of EI or is it EL used in posts, what does it stand for?
 
I have checked the board topic but couldn't see it (maybe it could be added to the Acronyms pinned list if it is that common)
 
Thanks in advance
 
Blessings

 

[daizeUK]

Estimative Index - a system of fertilization dosing.  The principle was developed by Tom Barr and basically means giving the plants as many nutrients as they can possibly use, ensuring that there is never a shortage of any nutrient, with the understanding that an excess of nutrients is not a cause of algae.