Question: How to measure nutrient concetration in hydroponic system?

Aleksi12358 is asking a question about spectrometry
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by Aleksi12358 | July 07, 2018 21:45 | #16659

Reason I want to do this is so that I can measure plants uptake of different nutrients and add right nutrients to reservoir with automated nutrient dispenser. Plants I want to study are salad, tomato, chili peppers, cucumber and strawberry. Maybe I will grow some other food plants later but these are what I would start with.

Is it possible to use spectrometer for analysis of nutrient concentration in solution? I want to measure as many different nutrients as possible. If it is possible could someone link me some literature about using spectrometer for nutrient concentration analysis?

I am open to other analytical methods to measure nutrient uptake if anyone knows better ones. I think ion selective electrodes with artificial neural network would be quite cool for analysis of nutrient solution but it seems to be too expensive for me as single electrode is multiple hundred €. I am looking something hobbyist can buy or build with max ~1000€.

Thank you.


Hi, which nutrients are you hoping to measure?

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I would like to measure every plant nutrient from macro to micro but I think macro nutrients(nitrogen, potassium, phosphorus, sulfur, calcium and magnesium) will be enough for start.

I did find one article about using infrared spectroscopy to measure nutrient levels. It works for macro nutrients. Here is link to it: Is it possible to turn public lab spectrometer to infrared spectrometer?

If there is possibility to use Open lab spectrometer to measure nutrient levels. Could it work that I make hole in bottom of cuvette and lid that has hole and run nutrient solution from reservoir trough cuvette back to reservoir? This way I could gather real time data. Real time data is not necessary but I would like to automate gathering of data at some point and this seems to be simplest way.

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I have very little experience with soil testing. So the local extension agent was called. He suggested the lamotte NPK test kits. One that will do 50 tests and costs about $30. He hadn't used it on hydroponics. But at that cost, it's worth a try. It's a visual test. No instrumentation is needed. By the way, amazon also lists a lamotte total test kit that will analyze for 14 different characteristics ( but only once), also for about $30. Its also for soil, not hydroponics.

Good luck

Thank you for suggestion. I will look into it.

Lamotte produces hydroponic test kit but it is over 300$ for 4 nutrients. Problem with test meant for soil is that they dont show results as ppm or mg/L but as lb/acre. I contacted them and asked if they can offer some kind of solution for me. I am anyway going to test Lego spectrometer with photometer reagents.

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Hi, just for starters there are a couple interesting projects related to nitrate detection here:

There's also this related question:

This page

But this seems the most promising!! --

And in case there are updates from others, let's see if @Frikkie or @winsorje have something to add?

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So it is possible to use spectrometer as colorimeter.

Is it possible to choose to read narrow band of spectrum with Public lab spectrometer software?

If I have understood correctly colorimeters work on some narrow area of electromagnetic spectrum that you can choose in some models and some has it predetermined. Different analyses need different area of spectrum because different solutions you get with chemical reactions that you do before analysis with colorimeter absorb different areas of electromagnetic spectrum.

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Yes definitely the diy spectrometers on this site can have their range narrowly selected. See for some examples!

That is so good! I will order Public lab spectrometer or parts for it from somewhere and few photometer reagents so that I can do some tests so that I know how accurate data I can get. I will let you know how it went. This might take week or two as I have to order everything online.

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The public lab instrument will cover a part of the NIR. Unless you can find very cheap used FTIR, the cost of the instrument will far exceed your budget.

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Also Markos, from the spectrometry mailing list, chimed in with😀

Hi, I apologize for sending here a reply to the question proposed at: but I tried to login to post an answer but I forgot the password and tried to reset but I didn't receive a confirmation email. So I am sending here the links that might be useful for the question proposed:

The system stores the different reagents in syringes. And the reagents are added in a mixing syringe containing a magnetic stirring system and the color generated (depending the composition) is analyzed by a camera. So far, as I understand it, the whole system is controlled by a RaspberryPi. A project to inspire other projects on the Water theme. Best Regards, Markos

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Thank you for links. I will contact person who designed that automatic water tester and ask few question about accuracy of readings and use of different reagents so that it would be possible to measure more nutrients. Maybe that auto tester can be combined with spectrometer for better accuracy.

Good day, i would like to ask on how did you manage to measure the nutrient uptake of a plant. i am currently doing a thesis for the measurement of nutrient uptake of a tomato plant. i dont know where to start in making the system. it would be appreciated if give your feedback.

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