My Kratky tomato project, tracking a Kratky setup from start to finish

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Fully passive, hydroponic setups are now everywhere. However, it seems no one has taken the time to diligently record how the nutrient solution changes through time in these setups and what problems these changes can generate for plant growth. In my Kratky tomato project, I will be closely monitoring a completely passive Kratky setup from start to finish. In this post, I will describe how this project will work, what I will be recording, and what I’m hoping to achieve. Check out the youtube video below for an initial intro to this project.

Introduction video for this Kratky project.

The goals

It is tough to grow large flowering plants using truly passive Kratky setups (read my blog post on the matter). We know this is because of issues related to their increased water uptake and the large nutrient and pH imbalances these plants create in nutrient solutions. However, I haven’t found any data set that shows how these problems develop as a function of time. By measuring different variables in a Kratky setup through an entire crop cycle, I hope to gather data to help us understand what goes wrong, why it goes wrong and when it goes wrong. With this information, we should be able to develop better nutrient solutions and management techniques, for more successful Kratky hydroponic setups for large flowering plants.

The setup

The setup is a 13L bucket wrapped in duct tape – to prevent light from entering the system – with a hole at the top and a net pot containing a tomato plant. The tomato – which I have named Bernard – is an indeterminate cherry tomato that was germinated in the net pot. The net pot contains a medium consisting of 50% rice hulls and 50% river sand. The bucket has been filled with a store-bought generic hydroponic nutrient solution up to the point where it touches the bottom of the net pot. Furthermore, the bucket is placed inside a grow tent and receives 12 hours of light from a Mars Hydro TS 600 Full Spectrum lamp. The light has been initially placed around 10 inches above the plant and will be moved as needed to maintain proper leaf temperature and light coverage of the plant.

The experimental Kratky setup. You can see the project box housing the Arduino and sensor boards at the bottom. Bernard has been growing for 2 weeks and is already showing its second set of true leaves.

The measurements

I will be monitoring as many variables as I can within this experiment. To do this I have set up an Arduino MKR Wifi 1010 that uses self-isolated uFire pH and EC probes, a BME280 sensor to monitor air temperature and humidity, and a DS18B20 sensor to monitor the temperature of the solution. I will also be using Horiba probes to track the Nitrate, Potassium, and Calcium concentrations once per day. All the Arduino’s readings are being sent via Wifi to a MyCodo server in a Raspberry Pi, using the MQTT messaging protocol. The data is then recorded into the MyCodo’s database and also displayed in a custom dashboard. The ISE measurements are manually recorded on a spreadsheet.

The dashboard of my MyCodo server, showing the measurements of the system as a function of time. All readings are also recorded in the MyCodo database for future reference and processing.

Furthermore, I am also taking photographs every 15 minutes – when the lights are on – using a smartphone. This will allow me to create a time-lapse showing the growth of the plant from the very early seedling to late fruiting stages.

Conclusion

I have started a new project where I will fully record the complete development process of a large flowering plant in a Kratky setup. We will have information about the EC and pH changes of the solution, as well as information about how different nutrient concentrations (N, K and Ca) change through the life of the plant. With this information, we should be able to figure out how to modify the nutrient solution to grow large flowering plants more successfully, and what interventions might be critical in case fully passive growth is not possible.

I will continue to share updates of this project in both my blog and YouTube channel.

What do you think about this project? Do you think Bernard will make it? Let us know in the comments below!

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5 Comments

  • Art
    May 7, 2021 @ 10:05 am

    Hi Daniel, thank you for your work, this should definitely be interesting analysis eventually!

    From my experience, one of the problems in Kratky is the lack of aeration, comparing to active DWC setups, however aeration with an air pump brings up a bunch of other issues like dirt, mold, unstable pH and some such, or until you put a bio-filters in. As you may know, the roots absorb oxygen from the solution so large air bulbs just go away anyway, so that is definitely not the best solution – there should be something generating smaller pieces of air.

    I’ve also seen examples when several Kratky buckets were installed side by side to a larger DWC container (like 6×10 feets) which was also passive, and the results from the latter were much-much better than former. As far as I understand, this is because oxygen is injected into the solution as a thin layer by atmosphere. I think there should be a rule of thumb / table of the dissolved air in a solution which can definitely be estimated.

    I have never tried any of dissolved oxygen meters so can’t say if they work as expected, but would it be possible for you to add this metric as well?

  • Dave Eargle
    June 8, 2021 @ 4:26 pm

    > Horiba probes to track the Nitrate, Potassium, and Calcium concentrations once per day

    Which probes did you use, and would you recommend them?

  • Raph
    May 16, 2022 @ 5:45 am

    “The ISE measurements are manually recorded on a spreadsheet” Are you still manually recirding it? It was in 2021, Any up dates on the tomatoes?

    • admin
      May 16, 2022 @ 8:18 am

      Thanks for commenting! There are several videos about this project on my youtube channel. The tomatoes did great until I forgot to add more water one week – when the plant was very big – and the plant died. I harvested a good amount from the plant before though!

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