When growing plants without soil, they must be fed with a hydroponics fertilizer which is a different mixture than what is contained in a soil garden fertilizer.
Plants in a soil garden need certain trace elements which can be commonly found in soil almost anywhere – therefore most commercial garden fertilizers do not include these elements in their fertilizer mix. Such elements include calcium, magnesium, and sulfur, to name a few.
Typical Hydroponics Fertilizer
This is a typical hydroponics fertilizer mix with the percentage of each chemical in the mix.
| Nutrient | Amount % |
| Potash | 22% |
| Nitrogen | 10% |
| Phosphoric Acid | 8% |
| Calcium | 5% |
| Magnesium | 1% |
| Sulphur | 2% |
| Boron | .05% |
| Copper | .05% |
| Iron | .2% |
| Manganese | .05% |
| Molybdenum | .05% |
| Zinc | .05% |
| Inert compounds | 51.55% |
If you do your own comparison of the above mix with a soil garden fertilizer you may find different chemical names from above – such as Phosphate and Potassium.
Phosphate is a salt of Phosphoric Acid so in this situation both chemical names can be viewed as equivalent. The same applies to Potash and Potassium. Potash is really potassium carbonates mixed with potassium salts.
I must stress, once again, that if you do not use a fertilizer specifically made for hydroponics, you are asking for trouble.
Hydroponics Fertilizer & Regular Fertilizer Comparison
This is a comparison of a typical hydroponic nutrient fertilizer blend with three commercial fertilizers for soil gardens. The comparison is between my ‘generic coverage’ brand of hydroponic nutrient mix, ‘Miracle Gro’ in powder form, ‘Miracid’ which is basically ‘Miracle Gro’ for acid loving plants and ‘Osmocote’ which is a special blend for vegetable bedding and early propagation.
| Element | Hydroponic Blend | Miracle Gro | Miracid | Osmocote |
| Potash | 22% | 10% | 15% | 14% |
| Nitrogen | 10% | 30% | 15% | 14% |
| Phosphoric Acid | 8% | 10% | 8% | 14% |
| Calcium | 5% | – | – | – |
| Magnesium | 1% | – | – | – |
| Sulphur | 2% | – | – | – |
| Boron | .05% | .02% | .02% | – |
| Copper | .05% | .07% | .07% | – |
| Iron | .2% | .325% | .15% | – |
| Manganese | .05% | .05% | .05% | – |
| Molybdenum | .05% | .0005% | .0005% | – |
| Zinc | .05% | .07% | .07% | – |
| Inert compounds | 51.55% | 48.46% | 60.61% | 58% |
Except for some missing elements, the 3 commercial blends aren’t too far off from the hydroponics nutrients mix – but they are ‘off’ enough to mean the difference between success and failure when growing hydroponics plants.
So… if you do not choose to use a commercial blend of hydroponic fertilizer nutrient then the next best would be to mix your own. It would certainly be possible to measure and add in the missing elements to get a balanced hydroponic fertilizer but not advisable – that is a science all its own.
Larry Maki is an avid, self-taught hydroponics gardener from Connecticut with a passion for alternative types of gardening.
Related Articles & Free Email Newsletter Sign Up
Container Hydroponic Systems are Great for Beginners
Passive Hydroponics for the Home Hobby Grower
Required Daily Maintenance for a Hydroponic System
Subscribe to our Free Email Newsletter
Comment here