I Only Use One Fertiliser For Soil AND LECA Plants (But You Need The Right Type Of Fertiliser

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Yes, you can use hydroponic nutrients in soil, but you may want to adapt the dosage.

In many cases you would use a lower dosage of nutrients for soil plants, because they can also obtain nutrients from their substrate.

What is hydroponics?

Hydroponics is growing plants using water as a substrate rather than soil.

Why grow plants hydroponically?

  • It’s less messy
  • You can schedule your care
  • You can control the nutrition

There are other reasons that make it useful for farming – for example you can build systems that allow you to make better use of available space.

How are hydroponic nutrients different from soil fertilisers?

Soil fertilisers primarily focus on the macronutrients NPK (nitrogen, phosphorus, potassium). They vary widely and come in all iterations of ratios. Some have added copper or calcium, but there’s a wide variety of different fertilisers that suit different plants.

This is because the plant will have nutrients available to it from the soil, so the fertilisers are more of a vitamin than a food source.

If your plants are growing so quickly that you’re regularly repotting them and adding more oil, you may never need to fertilise (though it would encourage optimal growth).

Plants grown hydroponically, however, receive very few nutrients from the soil, so their fertiliser has to be more complete. It’s more substantial than a vitamin – more like a medication – though plants get their actual energy from light.

Can you use hydroponic nutrients in soil?

Yes. In fact, all of the hydroponic nutrient labels that I’ve seen have the dosage information for both soil and water on them.

Whilst hydroponic nutrients have been specifically formulated to grow plants optimally in hydroponic conditions, they’ll work just as well in soil. Soil is pretty good at transferring nutrients from water to roots – better than just water, hence hydroponic nutrients needing to be developed in the first place.

There are some fertilisers that are intended to be used with soil that contain all the micronutrients needed, but they aren’t suitable for hydroponic use.

Nutrient lock-out can occur if the nutrients aren’t mixed correctly, or don’t have the correct composition – that’s why you need three separate bottles for the GH Flora series.

It would be easier for everyone if they mixed them ll together, but that stops the nutrients from working properly.

Also I quite like to feel like a scientist when I’m mixing them up.

I use the General Hydroponics Flora series as my only fertiliser, purely because that’s what I have and there doesn’t seem any point in buying more when I have three huge bottles to use up.

I do think it’s more effective than the seaweed fertiliser I used to use, but only because I measure out the dosage properly. To be honest, there isn’t that big of a difference, so I wouldn’t advise that you rush out and buy hydroponic nutrients if you only have soil plants.

However, if you have some leca and some soil plants, I’d definitely encourage you to just use one lot of nutrients, if only because it’s easier.

What’s the problem with using hydroponic nutrients in soil?

The main issue that can happen with using hydroponic nutrients in soil is that you can get a buildup of salts.

To be honest, unless you’re growing plants that you’re going to eat, I wouldn’t worry unduly about this. Unless you’re overfertilising, its unlikely to become too much off an issue.

Overfertilising is unlikely to occur unless you’re fertilsing more frequently than once a month. If you think your plants need more nutrition than this, then you can supplement their feed with more natural things such as worm castings.

If you’re still concerned about mineral buildup in the soil, or you’re growing edibles such as chillis, you can incorporate flushing the soil into your house care routine.

For those of you familiar with keeping plants in leca, you’ll be aware of flushing. Though to be totally honest, I’ve largely stopped flushing my leca plants. The buildup didn’t rinse away so I (rightly or wrongly) decided that if flushing didn’t remove the buildup, then it probably wasn’t going to be an issue for my plants. Mainly I’m just lazy, but my plants are fine!

How to flush your house plants

I have a whole article on flushing here.

Flushing is just the process of top watering your plants a few times. I pour the water through slowly a couple of times, and then speed up. I can’t really articulate why I do this, in my brain I just think that its the most effective way to go about it.

Final thoughts

I’ve used hydroponic nutrients as the main fertiliser for my soil plants for the past year or so, and I haven’t noticed a change in my plants, either for the worse or better. Perhaps if I flushed them more regularly, I’d see more of an impact. Perhaps in the summer (probsbly not though!)

In conclusion, if you have hydroponic nutrients that you want to use up, then go ahead and use them in your soil plants – they’re just as effective as soil nutrients, and may be extra helpful if you use a heavy coir mix (or perlite – anything that doesn’t contain any nutrients).

However, if you use a fairly nutritious soil mix, then don’t think you have to rush out and buy hydroponic nutrients.

Caroline Cocker

Caroline is the founder and writer (and plant keeper) of Planet Houseplant

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