Understanding Hydroponics Fertilizers Labels

understanding hydroponics fertilizers labels

Understanding Hydroponics Fertilizers Labels

…from Plants are Basically Electric (Michael Christian, American Hydroponics)

The first step to being able to create hydroponic nutrients is to understand the difference between soil nutrients and the requirements of plants. Most gardeners are familiar with soil nutrients such as those called by the numbers 20-20-20, but what does 20-20-20* really mean?

One might assume N.P.K ratio means 20% Nitrogen (N), and 20% Phosphorous (P), and 20% Potassium (K). (*Powdered hydroponics fertilizer)

No, it’s not that simple. It’s 20% Nitrogen (N) and 20% Phosphorous Pentoxide (P2O5) and 20% Di-Potassium Oxide (K2O). (Depending on the country of origin, these units change by continent.)

This translates to the actual % of the N.P.K as follows:
20% Nitrogen (N), 8.8% Phosphorous (P), and 16.6% Potassium (K).

However a good hydroponic nutrient contains all of these plus all the other minerals required for healthy growth. They will also be in the correct ratio to each other, according to plant type, and stage of growth, e.g. vegetative, flowering or fruiting stage.


The minerals required for good growth are as follows:

Macro elements:

Nitrogen (N)
Phosphorous (P)
Potassium (K)
Calcium (Ca)
Magnesium (Mg)
Sulphur (S)

Micro elements:

Iron (Fe)
Manganese (Mn)
Boron (B)
Copper (Cu)
Zinc (Zn)
Molybdenum (Mo)
Sodium (Na)
Chloride (Cl)
Silicon (Si)

There are other minerals found in plant tissue when analyzed, but for our purposes these are the main requirements for hydroponic growing, and the ones we have to monitor.

reading hydroponics fertilizers labels

Above: Liquid hydroponics fertilizer 

About the Author:

Michael Christian is President of American Hydroponics, with over 30 years experience in offering hydroponic production expertise and technologies across the globe.


About Erik Biksa 236 Articles
Erik Biksa has been writing about and discussing hydroponics growing, related technologies and cropping methods since 1999 in a variety of professional publications and platforms globally Erik has travelled the world learning and teaching modern growing techniques and technologies and is appreciated by many growers for his informative yet hands on approaches. Presently, he is the Editor at Grozine Hydroponics Mag.


  1. I have a question. if a person needs to eat organic for health reasons to avoid chemicals, then wouldnt mined nutrients be as healthy for them as organic.

    • yes and no. mined minerals may have unhealthy impurities.they may also not be soluble for absorption in a natural state-some are, some are not. just like synthetic fertilizers or organic fert materials, there are different grades of minerals, where purity as a % counts. It’s a common misconception that organic always means healthier–just like the ferts and minerals mentioned, there can be plenty of unwanted stuff, eg. heavy metals with organics–all three are regulated (eg. Ag Canada or Canadian Food Inspection Agency) when from proper sources. Field grown, however, tends to be very “chemmy”. When food is grown with very pure fertilizer and harvested in a very healthy state hydroponics crops offer a lot nutrition in a very “clean” form. have seen nutritional and “contaminant” reports go both ways for either Organic or Hydroponic….field grown usually takes 3rd every time, ie grow your own!

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