How to use the Kratky Method with 3-part Hydroponic Nutrient Solutions

What is the Kratky Method?

The Kratky Method is a simplified hydroponic system in which the plants are suspended above a reservoir containing a nutrient solution. As the plants access the water, the nutrient solution levels fall. As the solution levels get lower, the roots of the plant grow downwards to access more resources. This is merely a simplified introduction to the method, and those interested should research more thoroughly before attempting it. Today we will focus on applying our Holland Secret 3-part Fertilizer to the Kratky Method of growing using hydroponics. 

Hydroponics is a soilless growing medium in which you grow plants in liquid. Generally they are grown in a nutrient solution mixed with water.


What fertilizers should I use?

The fertilizers used for this method are relatively simple, consisting of a 4-18-38 blend, Calcium Nitrate, and Epsom salt. However, in Canada the 4-18-38 blend is not available resulting in those wanting to use this method often finding issues figuring out a proper feeding program. That’s where we come in! Using a 3-part system offers huge amounts of flexibility, as changing the ratios can allow for the replicating of most feeding programs.

We recommend our Holland Secret 3-Part Fertilizer:





What measurements should I use?

We did the hard part for you and looked at the amount of each individual nutrient that this feeding program is providing the crop and made adjustments accordingly. From that, this is what we recommend:


Per 4 liters (1 gallon) of water use:
7 mL Holland Secret Grow
7 mL Holland Secret Micro
7 mL Holland Secret Bloom 


Note: It is a lucky coincidence the measurements for each nutrient came out equal! When using a nutrient solution of another brand measurements may vary. 


For growing leafy greens we recommend increasing the nitrogen and lowering the phosphorus. 

Per 4 liters (1 gallon) of water use:
10 mL Grow
7 mL Micro
4 mL Bloom 



Don't worry about the flushing stage for vegetables, we only recommend flushing for crops that are meant for smoking!



The premise behind Kratky is you add a fairly weak solution of nutrients and as the water is used up the fertilizers will also be used up! This keeps the salinity from going too high and the grower won't have to do much further adjustment. 



If you plants start wilting or the leaf tips turn brown, the solution has gone too strong (due to evaporation) and water should be added or your solution replaced. 


Extra Tip:

For those of you interested in using the Kratky Method on tomatoes, we recommend supplementing with a Calcium and Magnesium nutrient as tomatoes have a high demand for Calcium. Do not add to the initial solution as it may be too strong for a young plant. Instead, add our Calnesium or Organical Magic nutrient once flowering begins. Add at a rate of 8 mL per 4 liters (1 gallon) for the remaining volume of nutrient solution (not the initial volume of solution you started the plants out with). 


Like other hydroponic methods, always remember to keep a close watch on pH and TDS levels (total dissolved solids). This is most important in warmer conditions as water may quickly evaporate and render the solution too strong which could damage the plant. 



Good luck! And remember you can always reach out to @futureharvestdevelopments on instagram if you have any questions or need advice.

    Published by Loren Price

    Loren, the Director of Fertilizer Technology at Future Harvest, grew up on a mixed grain and cattle farm in North West Saskatchewan. He went on to study biotechnology and worked in agrosciences in Saskatoon for several years before moving on to Future Harvest and the hydroponic plant food industry. Starting off in fertilizer production, his focus is now on fertilizer formulations and regulatory affairs. His areas of expertise include: agronomy, analytical chemistry, plant tissue culture, plant breeding, molecular biology, and plant nutrition. Outside of work, Loren collects vintage concert T-shirts and is an amateur craft brewer specializing in historical and lesser known styles of beer.


  • Feb 06, 2020
  • Category: Articles
  • Comments: 6
Ben December 22, 2020

I am growing some veggies such as kale, Swiss char, bok choy, parsley, etc and using you nutrients.

They are only seedlings at the moment but do I need to a flush cycle once they hit the point of being edible?

I am going to use the Kratky Method with some bubble stones. Ph will be around 5.5-6.0.

I have been reading that you can simply add water and nutrients to a 5 gallon bucket and forget about it until the 30+ days is done and eat away. Would I use the above mentioned levels of 7mg for each nutrient per 4 Gallons?

Thank you for your help!

Future Harvest December 22, 2020

Hi Ben!

The directions given on the blog post are optimized for tomatoes since you’re growing leafy greens I would change it up to increase the nitrogen and lower the phosphorus. Grow 10 ml, Micro 7 ml, Bloom 4 ml per 4 liter. Don’t worry about the flushing for vegetables, this stage is really only relevant for crops that are meant for smoking.

The premise behind Kratky is that you add a fairly weak solution of nutrients and as the water is used up the fertilizers will also be used up keeping the salinity from going too high and the grower won’t have to do much further adjustment. Do keep an eye on everything though, and if the plants ever start wilting or getting brown on the leaf tips the solution has gone too strong due to evaporation and water should be added or ideally replaced. Kratky is a simple water culture system and is good for beginners, hopefully once you’ve mastered it you’ll consider moving on to a recirculating system which will have significantly better yields.

Neil Stapley March 01, 2021

So I am building a triple pot gravity fed system (got the plans from a YouTuber called Hooco) any who the 8 buckets are fed from a 30gal reservoir. I want to mix up the veg I grow peppers tomatoes cucumbers etc no leafy greens can they all be fed from the same nutrient mix? I have a 2nd reservoir for the leafy greens.

I always run before I can walk this is my first system build

Future Harvest March 01, 2021

Hi Neil, the Kratky method is more designed for those who are making up one nutrient solution and are just letting their plants sit in the same solution through their whole life cycle. It sounds as though you’re using a more advanced method and in which case I would recommend using the direction on the bottle which changes up the ratios throughout the life cycle.

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