Can Hydroponic fertilizers be used in soil ?

Question

If so at what strength

Answer 1

Unless I overlooked something it shouldn't be a problem. Find the NPK of whatever product you are using and adjust accordingly. Mixing too strong will cause problems.

MiracleGrow Liquafeed, which is made for soil, has a NPK of 12-4-8. Following the directions of mixing 1 ml / L would result in a dilute NPK of .012-.004-.008.

Two brands of hydroponic nutrients by comparison:

FloraNova Grow is 7-4-10. If we also diluted at 1 ml / L  (aka 1 part per thousand) we would get a dilute NPK of .007-.04-.010

Ionic Grow is 3-1-5. If mixed at 3 ml / L would be .009-.003-.015.

That said I wouldn't run out and buy hydroponic nutrients to use on a soil garden. If you have a bunch of half full hydroponic nutrient bottles getting in your way that's understandable. Just keep in mind that Liquafeed costs around $10 for the 64 ounce refill pack and Floranova costs about $20 for a 32 ounce bottle.

These products were simply used as examples and I'm not trying to endorse any of them.

Answer 2

No they are too weak.