13 ms·

What elements does a plant need to grow?

339 points by lathyrus_long 5y ago

chilling 5y ago
Nice work. I really admire your hardware setup. However it's worth adding that most of blooming plants will change their 'diet' during their flowering period. Some will continue to grow through the whole cycle on one mix and other (like tomato, cannabis) need some additional nutrients dj'ing. I've been growing succesfully 'passiflora edulis' in hydroponic setup for 3 years (continuously) and still I'm using hydroponic as a great kindergarden for most of my new plants.
- lathyrus_long 5y ago
  > However it's worth adding that most of blooming plants will change their 'diet' during their flowering period. Yeah, absolutely. I tend to grow a lot of different plants at different life stages, so an optimal profile for each one would be a lot of work. I'm certainly paying a cost in yield for my laziness, though. At some point I should redesign my nutrients into three parts. I've got support for a fourth dosing channel (fertilizer A, fertilizer B, pH, spare) in my electronics, so it's just another pump and the plumbing.
71a54xd 5y ago
Soilless media (commonly used for growing marijuana) was actually a game changer in my apt for indoor plants during the pandemic. If you have any issues with fungus, gnats or any kind of negative root insects soilless media is the way to go. Fertilizers that incorporate beneficial endophytes are also fascinating. However, steer clear of nutrient blends like Noot though - they're watered down and urea derived which is a great way to stress and kill your house plants.
- lathyrus_long 5y ago
  > If you have any issues with fungus, gnats or any kind of negative root insects soilless media is the way to go. Yeah, though with the caveat that if your medium retains water very effectively (as e.g. rockwool does) and is exposed to light, then it may grow algae. The larvae then feed on that algae, and the problem is back. I spend a lot of time fighting fungus gnats. The best option is always to adjust growing conditions to create an inhospitable environment for them, but I also make recourse to Bti (a bacterial toxin, like mosquito dunks) or pyrethrin sometimes.
  - chilling 5y ago
    Other way to fight this issue is using a pre-made friendly fungy & bacteria mix.
    - aaron_m04 5y ago
      What do you make this mix out of?
      - chilling 5y ago
        I don't know how to make them out. My preferred solution (used in both soil and hydroponic) is GHE SubCulture[1] But any should work just fine [1] https://growx.ru/images/catalog/GHE/stimylatori_i_dobavki/subculture_ghe.jpg https://growx.ru/images/catalog/GHE/stimylatori_i_dobavki/su...
alfor 5y ago
It was found that plants roots are in symbiosis with bacterias and fungus to get minerals from the ground. I think that like us with our microbiome, the plants have evolve with their microbiome in the soil. To grow them from a chemical mixture is to oversimplify nature. Alternatively, you could use a coarse sand bed as media and ’compost’ natural fertiliser and get beneficial bacteria and fungus going.
- the_pwner224 5y ago
  > It was found that plants roots are in symbiosis with bacterias and fungus to get minerals from the ground. ... To grow them from a chemical mixture is to oversimplify nature. And it's been throughly and exhaustively 'found'/demonstrated/proven that plants grow very well in hydroponic systems. And depending on the exact plant & nutrients used, can be just as nutritious, or more, or less nutritious compared to soil grown plants (also depending on how the soil plant is grown). Natural != the best way to do it. (note: I'm not saying bacteria/fungi can't be beneficial)
bravogamma 5y ago
Wonderful job and congrats, this looks awesome. Are there any sources (books, papers, websites, etc.) you (or anyone here) can recommend for further reading about the science behind the elements a plant needs to grow?
- lathyrus_long 5y ago
  "Soilless Culture: Theory and Practice" is a pretty good textbook. I also recommend the USDA's https://www.fs.usda.gov/treesearch/pubs/46345 https://www.fs.usda.gov/treesearch/pubs/46345 That's not about hydroponics, but the theory behind sophisticated growing in containers of soil-like potting mix is almost the same.
lathyrus_long 5y ago
I've been growing hydroponically through the pandemic. I'm now switching from commercial pre-blended nutrients to my own design, customized for my hard water and blended from individual salts. In the linked article, I briefly review the biochemistry, show the fertilizer design calculations using an open-source tool that I wrote, and review a lab analysis of the final solution. This is a fair amount of work, and I'd guess that relatively few non-professional growers would bother. I hope this may be interesting to anyone generally curious about plant nutrition though, or about the design of modern complete chemical fertilizers.
- holonomically 5y ago
  Very cool. Thanks for putting this together.
- dkarp 5y ago
  Very cool. Do you have any pictures of the full hydroponic setup (with plants)?
  - itsgrimetime 5y ago
    also interested in seeing pictures/diagrams of the setup
  - lathyrus_long 5y ago
    There's one in my post about the automation system, at: https://old.reddit.com/r/Hydroponics/comments/o8j68n/singleboard_automated_phecdosingmore_seeking_devs/ https://old.reddit.com/r/Hydroponics/comments/o8j68n/singleb... That was still with the old commercially-blended nutrients, though. I've so far used my custom blend only for a few bok choy, as a final quality control check since they're fast-growing. If those continue to look good, then I'll move my entire balcony to the custom blend in about a month.
    - jcims 5y ago
      Regarding the automation, I built a DIY closed loop distillation process with similar i/o requirements. I have nowhere near the skill required to build a dedicated board but found that node-red running on raspberry pi using mqtt to talk to nodemcu running tasmota created an extremely extensible and modular platform. I’m running 8 thermocouples, two pumps, two flow meters, two load cells, current sensing coil and zero crossing ssr to chop current to a 6kw 240v heating element. With tasmota the little mcus are just kind of like legos and i just put them where the wiring is convenient and keep some spares. All of the i/o is dumb, the control loops are all on the node-red flowgraph allowing for lots of visibility of terms when tuning pids. The node-red dashboard lets you mix telemetry and control on a very touch friendly format, and i spool all of it to influxdb to compare runs over time. I’m sure you’ve got what you need with what you’ve built but at a minimum node-red might be worth a look. I was suuuper impressed using it for this.
adriand 5y ago
What's insane to me is how much certain plants will grow in tap water with zero regard for their nutritional requirements. I frequently propagate houseplants by putting cuttings in a glass of water and sometimes I get lazy and don't re-pot them for weeks or even months. And they will often grow very well - shooting out tons of roots but also additional leaves and stems.
- GhettoComputers 5y ago
  That’s the same as saying there are animals that have more biological fitness (mice) than others (pandas). Carbon and nitrogen come from the air, water will hydrate them, but most plants have expectations. Orchids for instance can be artificially bloomed with phosphorus but if it was dormant people would just think it’s dying, as if natural cycles of less bloom was a failure of the plant’s growth!
- soperj 5y ago
  Bottoms of green onions to me are the weirdest. You can get multiple cuttings just from water.
  - 71a54xd 5y ago
    Hard water is actually one of the worst things you can give to expensive house plants, distilled water is by far the best option to prevent root calcification and ph swings.
    - lathyrus_long 5y ago
      You can also acidify the water down to a reasonable pH, though even phosphoric acid is somewhat dangerous and the best choices (nitric or sulfuric) aren't something I want in my apartment. Amateur hydroponic growers often use reverse osmosis water, somewhat wasteful but cheaper than distilled. You can get RO systems designed for aquarium use with no pressure tank at the output and just let them slowly fill a barrel or tote, over hours or days.
    - soperj 5y ago
jazzyjackson 5y ago
I came by a book on "micro-propagation" once (getting diced up plant samples to root in a petri dish) - it discussed the old fashioned way to propagate orchids (once you have a mutation you like, you have to clone that one plant by however many you want to sell) - apparently coconut water was used as a nutrient medium. Found a source that discusses its use [0], apparently is has beneficial hormones as well, "Besides its nutritional role, coconut water also appears to have growth regulatory properties, e.g., cytokinin-type activity" [0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6255029/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6255029/
belval 5y ago
You know how sometimes you think about something and it appears out of nowhere the very next day? That's what this article is for me. I have been growing mint, basil, purple basil and rosemary in a custom NFT system for the last 5 months and I am starting to run low on my General Hydroponics nutrients which are somewhat expensive at ~100$ for the 3 solutions. This is very useful and I want to say a big thank you to the author for doing so much of the work I was planning to do!
- polishdude20 5y ago
  When you said NFT I got triggered. Then I realized this can't surely be the NFT I'm thinking about haha.
  - belval 5y ago
    My bad, should've known better than to use NFT on HN. For those wondering, it stands for "Nutrient Film Technique" and it's basically running a small stream of nutrient solution in PVC tubes with your plants' roots being somewhat submerged. It's a pretty water-efficient technique, this link explains it well: https://www.trees.com/gardening-and-landscaping/nutrient-film-technique https://www.trees.com/gardening-and-landscaping/nutrient-fil...
    - cwkoss 5y ago
      Have you considered selling your Nutrient Film Technique on the blockchain?
DaftDank 5y ago
It takes a lot of patience, and good IPM, but living soil has been awesome to me. We often say we grow soil, rather than plants, because of the fact a healthy living soil will provide all the nutrients the plant needs, and all you have to do is water essentially. Speaking strictly from a marijuana perspective (the limit of my experience with living soil), it makes the marijuana taste better and have a better smell. I've seen two different growers, starting with the same clones from the same mother planet, where one grows in soil using bottled nutes, and the other does living soil. The living soil definitely was superior. With that said, living soil is not practical for everyone. Trying to do it indoors where you also live could create issues if you do not have a good IPM strategy, and fully understand the soil food web. "Teaming with Microbes" by Jeff Lowenfels is an excellent book to learn about how the soil food web works.
- Baeocystin 5y ago
  What do you do about spider mites?
  - reydequeso 5y ago
    Sns217. Spider mites like it dry, so mist your plants and it may be a little wise to repot your plants or fertilize with cal/mag
- sampo 5y ago
  IPM = Integrated Pest Management
- wefarrell 5y ago
  So long growers are maximizing THC content and yield per area Hyrdo will outcompete organic soil. Personally I grow organic because I too prefer the taste and I really enjoy composting. However having grown in hydro I can tell you that plants grow bigger, faster, and more potent.
  - dr-detroit 5y ago
    By soil you mean cocoa right?
intrasight 5y ago
It's "what molecules" a better phrasing?
- lathyrus_long 5y ago
  "What ions", strictly--they're salts, so they dissociate when they dissolve. But it's conventional to look at the breakdown by element, not by ion, even in cases where the specific ion is important. For example, fertilizers give "percent nitrogen from nitrate" and "percent nitrogen from ammonium", not "percent nitrate" or "percent ammonium".
bastardoperator 5y ago
Outside of light, nitrogen (N), phosphorus (P), and potassium (K), or NPK for short Finding the right combination of these elements is what hydroponics farmers do everyday, pushing the limits of their crop for maximum quality/yield. We are starting to see a big shift in hydroponic fertilizers from liquid to powder since nobody wants to pay for shipping water. I highly recommend https://github.com/kizniche/Mycodo https://github.com/kizniche/Mycodo for anyone doing anything in hydroponics.
- zuminator 5y ago
  The article lists 16 required elements: C, H, O, N, P, K, Ca, Mg, S, Fe, Cu, Mn, Zn, B, Mo, Cl.
  - amelius 5y ago
    In what forms?
  - onecommentman 5y ago
    As do most other websites like https://agrilifeextension.tamu.edu/library/gardening/essential-nutrients-for-plants/ https://agrilifeextension.tamu.edu/library/gardening/essenti... Interestingly none of the critical semiconductor elements are required by plants: Silicon, Germanium, Gallium, Tin, Gold, Silver…
- Radim 5y ago
  > Outside of light, nitrogen (N), phosphorus (P), and potassium (K), or NPK for short Ehm. Check out this Nature article on the importance of Carbon: https://www.nature.com/scitable/knowledge/library/effects-of-rising-atmospheric-concentrations-of-carbon-13254108/ https://www.nature.com/scitable/knowledge/library/effects-of... Very readable and worth reading in full. Especially the effects of elevated CO₂ on the C₃/C₄ photosynthetic pathway and crop yields.
  - bshipp 5y ago
    Hydroponic growers are intimately aware of the need and benefits accruing from elevated CO2. You'd be hard pressed to find a greenhouse vegetable farm without a huge CO2 tank outside, as well as the technology used inside the scrub carbon dioxide from natural gas exhaust and reroute it into the plants. They tend to burn the natural gas during the day to feed the plants while storing the heat in huge water tanks to warm facilities at night. The primary constraint is maintaining low enough CO2 levels to remain healthy for the humans that work inside the greenhouse. Plants themselves can handle very high levels of carbon dioxide.
beebeepka 5y ago
This reminds me. In my layman's mind, having agriculture right next to roads is bad because vehicles are dirty. Recently, someone told that's not the case because "plants need this stuff". Any truth to that claim? I'm yet to read the article
- intrasight 5y ago
  Plants for sure absorb things they don't need, and that are toxic to themselves and to us.
- boldslogan 5y ago
  My childhood experiment actually comes in handy! I can confirm at the least that planting half of the same batch of seeds close to a road's (the tarmac's) edge next to it, and in a forest, my grass seeds grew much worse next to the road. Also I was told to never eat berries growing from a bush close to a road since they are more dirty.
- godDLL 5y ago
  Roads used to be full of gasoline drip, heavy metals from exhaust and such. Plants would suffer but absorb it and pass it on to you if you eat them. Nowadays not so much. Specifically around 200 times less so. Not worth consideration. Whatever comes from the road is usually baked by the sun, so no nutrients left there. No need for that. I can't come up with another way of analysis for this claim without it being more specific, but generally, no, that's not working today.
spaetzleesser 5y ago
Brawndo has what plants crave. It’s got electrolytes Idiocracy
- dangerboysteve 5y ago
  This was the very thing thing which came to mind when I read the title.
- outworlder 5y ago
  They weren't even wrong. I would totally buy a Brawndo hydroponic formulation.
  - aaron_m04 5y ago
    The problem in Idiocracy was evaporation concentrating the ions until there was eventually too much for the plants to grow. I'm not sure what the solution is on real farms.
GhettoComputers 5y ago
Great post! This reminds me a lot of making dog food for people (aka Soylent) with the best profile, requirements, and because plants don’t complain about taste, you’ll have no problem with ratios! The only issue is about the effects of these elements and what they can do to the water or your home. Would they need a special environment to prevent fungi, algae, bacteria or mold that would also feast upon these nutrients? You said bacteria didn’t always appear but what if some will grow on hydro? What optimizations would you do for preventing infections?
- lathyrus_long 5y ago
  Some growers keep their reservoir and root zone as sterile as possible, using additives like hydrogen peroxide or calcium hypochlorite. Others dose beneficial bacteria intended to outcompete bad stuff, like Bacillus amyloliquefaciens (Hydroguard, Southern Ag Garden Friendly Fungicide). Algae can use the same nutrients as the plants, but can often be controlled by excluding light. Other bad microbes are generally heterotrophs, so they're feeding on something else (like dead algae or dead roots).
  - GhettoComputers 5y ago
    Is it possible to make an ecosystem that is beneficial, like kombucha in a way? Will they be using indoor lighting like from weed grow LEDs (red and blue) or you planning all/mostly natural lighting? This is a really cool project, do you have any plans with plant hormones? I only know I used rooting powder, this article is interesting! I used ethylene as well to ripen foods with bananas but I didn’t actually use them on my plants. https://untamedscience.com/biology/plants/plant-growth-hormones/ https://untamedscience.com/biology/plants/plant-growth-hormo...
    - lathyrus_long 5y ago
      I grow mostly by sunlight on my balcony. I've also got some white LM301B lights, which seem very popular among those growing by artificial light only. Greenhouse growers supplementing sunlight still seem to prefer red-blue. You could tell a story like "some intermediate wavelengths will improve yield, and you can get them either from white LEDs or from the sun", though I'm not sure how rigorous the evidence is for that. I don't think there's much about plant hormone use that's specific to hydroponics. People use rooting hormone and foliar sprays of plant growth regulators and such, but they do that in soil too.
kortex 5y ago
> Sulfuric acid or nitric acid would have a more favorable effect on the nutrient profile, but they're more and much more dangerous respectively. Sulfuric acid is not really that dangerous unless you are getting the high test stuff from a chemical supplier. You can use battery acid refill solution, it's just deionized water and H2SO4 at around 30% concentration. That's mild enough that it won't cause any immediate burns, but you should still wear gloves and goggles when handling it. There's no need for nitric acid, since you are already supplying nitrate ions.
- lathyrus_long 5y ago
  Yeah, battery acid is sometimes used, and not a terrible corrosive risk with the precautions you note. I don't love that it doesn't come with any specs e.g. on heavy metal contaminants, but I think it's near-certainly fine in practice. ACS grade would have specs, but I don't want to handle the concentrated acid. Sulfuric acid would give me excess sulfate, but since the plants aren't too sensitive to that I expect that would be an improvement over my current excess phosphate. I'm not sure if I'd get calcium sulfate precipitation as the reservoir concentrated. Nitric acid would let me hit my target profile exactly (with a corresponding decrease in nitrate salts), but it's way more dangerous. I've seen nitric acid used in academic trials and in countries with weaker safety laws, but not commercially in the USA.
  - kortex 5y ago
    Yeah, it's annoying there is no purity spec on the battery acid, but in all likelihood, it's pretty pure. One could always test it. I mean I bet nitric acid would work great for that purpose, it's just a bit more expensive and harder to get in some places, as you mention. It's definitely commercially available in the USA though. Duda diesel has it: https://www.dudadiesel.com/search.php?query=nitric https://www.dudadiesel.com/search.php?query=nitric Duda also has sulfuric which is likely higher purity, but you seemed to express some concerns about working with corrosives. I'm a former chemist, so anything short of super angry chemicals like piranha solution, I'm not too phased :D
comrh 5y ago
Really nice documentation, well done.
deleted 5y ago
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julienfr112 5y ago
Does someone have a system with arduino and concentration probe that match every nutriment individualy with it's exact optimal concentration ?
- flyingfences 5y ago
  I've looked into exactly that sort of setup for a previous job a few years ago and the problem is that these probes don't exist for every nutrient and the ones that do exist tend to be very expensive. It wouldn't be a cost-effective apparatus unless it was set up with one probe station metering the outflow to the whole of an industrial-scale greenhouse.
serverholic 5y ago
Question: How do we know that we are giving plants everything "we" need? We get nutrition through the food we eat and there are many, many molecules that contribute to our health. This project is cool but I worry about subtle nutritional deficiencies if this food ends up being the majority of a diet. I have the same worry when it comes to lab-grown meat.
- pjc50 5y ago
  An obvious question would be selenium; RDA is about 50 micrograms, and the upper "safe limit" is 400 micrograms. https://www.webmd.com/a-to-z-guides/supplement-guide-selenium https://www.webmd.com/a-to-z-guides/supplement-guide-seleniu... That's an extremely trace mineral.
- outworlder 5y ago
  Where would the plants store useless (to them) elements and for what purpose?
  - Djrhfbfnsks 5y ago
    I don't know the biology, so I can't answer specifically, but surely there are many cases of "useless" and even detrimental elements being stored in living bodies. Just look at heavy metal accumulation in animals for example.
  - serverholic 5y ago
    Water in the plant, cells, really anywhere. Same thing happens when we eat or drink something. Various molecules enter our blood, organs, etc.
- heurist 5y ago
  I work in hydroponic farming. If you live in the US then the produce you find in a grocery store has been grown and harvested in severely suboptimal conditions for human nutrition. Outcomes will vary across hydroponic systems but you will see in a few years that produce grown hydroponically under natural light 1) has higher nutritional density, 2) tastes better, 3) has a longer shelf life. Much of this is due to being harvested when the plant is ready and transported relatively short distances rather being harvested early for multi-week cold chain transport.
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stevespang 5y ago
professional degreed horticulturist here: 1) grinding your own ferts is nonsense, JR Peters makes the best, hands down. 2) I built my own RO system with permeate pump years ago for like $350 in parts off the internet, uses pressure bladder tank and solenoid on timer (dumps every 45 min or so) to fill a 55 gallon barrel every 24 hours. I use the largest ice maker hexametaphosphate cartridge filters to control the calcium and keep it soluble so it will not poison the RO membranes,I get about 20 days on each hexmetaphosphate filter cartridge. Ph control is done with sulfuric acid from Duda Diesel, 1/2 capful in 55 gallons of plain city water (not needed for RO water) - - comes out to about 6.5 after 24 hours. My water is in limestone country, about 450 ppm soluble salts. Duda used to sell the real deal,it was syrup like and super dangerous, now it's watered down crap, still it will burn you real fast. Always wear gloves, full face mask and apron. You can also use weak battery acid from auto parts store, weaker. Many orchid growers use more expensive citric acid, they keep it mixed in concentrate tank for days,they are not loosing it's strength in hours as you suggest.
flightless 5y ago
Great stuff. I was thinking about this after watching a talk by the Beyond Meat CEO in which he states that instead of using animals to rearrange plant proteins into animal proteins (muscles), they're taking the animal out of the equation. My next thought was, can't you take the plant out of the equation too? How difficult is it to rearrange these nutrients from a fertilizer mix straight into something resembling animal proteins (though easier for humans to digest)? I wonder at what point plants scale better than raw conversion of fertilizer to whatever protein these companies seem to be synthesizing.
lappa 5y ago
Interesting but I feel like I'm still missing an important piece of information to use this tool. Is there a resource which provides optimal nutrient ratios for different plants?
sydthrowaway 5y ago
Can this be used to feed a family apartment
tanbog5 5y ago
But how can anything grow without the most important thing: Love.
- godDLL 5y ago
  That's this man's expression of love for his crop right there, what are you talking about, you insensitive dolt.

339 points by lathyrus_long 5y ago

Nice work. I really admire your hardware setup. However it's worth adding that most of blooming plants will change their 'diet' during their flowering period. Some will continue to grow through the whole cycle on one mix and other (like tomato, cannabis) need some additional nutrients dj'ing. I've been growing succesfully 'passiflora edulis' in hydroponic setup for 3 years (continuously) and still I'm using hydroponic as a great kindergarden for most of my new plants.

lathyrus_long 5y ago
> However it's worth adding that most of blooming plants will change their 'diet' during their flowering period. Yeah, absolutely. I tend to grow a lot of different plants at different life stages, so an optimal profile for each one would be a lot of work. I'm certainly paying a cost in yield for my laziness, though. At some point I should redesign my nutrients into three parts. I've got support for a fourth dosing channel (fertilizer A, fertilizer B, pH, spare) in my electronics, so it's just another pump and the plumbing.

71a54xd 5y ago

Soilless media (commonly used for growing marijuana) was actually a game changer in my apt for indoor plants during the pandemic. If you have any issues with fungus, gnats or any kind of negative root insects soilless media is the way to go. Fertilizers that incorporate beneficial endophytes are also fascinating. However, steer clear of nutrient blends like Noot though - they're watered down and urea derived which is a great way to stress and kill your house plants.

lathyrus_long 5y ago
> If you have any issues with fungus, gnats or any kind of negative root insects soilless media is the way to go. Yeah, though with the caveat that if your medium retains water very effectively (as e.g. rockwool does) and is exposed to light, then it may grow algae. The larvae then feed on that algae, and the problem is back. I spend a lot of time fighting fungus gnats. The best option is always to adjust growing conditions to create an inhospitable environment for them, but I also make recourse to Bti (a bacterial toxin, like mosquito dunks) or pyrethrin sometimes.
- chilling 5y ago
  Other way to fight this issue is using a pre-made friendly fungy & bacteria mix.
  - aaron_m04 5y ago
    What do you make this mix out of?
    - chilling 5y ago
      I don't know how to make them out. My preferred solution (used in both soil and hydroponic) is GHE SubCulture[1] But any should work just fine [1] https://growx.ru/images/catalog/GHE/stimylatori_i_dobavki/subculture_ghe.jpg https://growx.ru/images/catalog/GHE/stimylatori_i_dobavki/su...

alfor 5y ago

It was found that plants roots are in symbiosis with bacterias and fungus to get minerals from the ground. I think that like us with our microbiome, the plants have evolve with their microbiome in the soil. To grow them from a chemical mixture is to oversimplify nature. Alternatively, you could use a coarse sand bed as media and ’compost’ natural fertiliser and get beneficial bacteria and fungus going.

the_pwner224 5y ago
> It was found that plants roots are in symbiosis with bacterias and fungus to get minerals from the ground. ... To grow them from a chemical mixture is to oversimplify nature. And it's been throughly and exhaustively 'found'/demonstrated/proven that plants grow very well in hydroponic systems. And depending on the exact plant & nutrients used, can be just as nutritious, or more, or less nutritious compared to soil grown plants (also depending on how the soil plant is grown). Natural != the best way to do it. (note: I'm not saying bacteria/fungi can't be beneficial)

bravogamma 5y ago

Wonderful job and congrats, this looks awesome. Are there any sources (books, papers, websites, etc.) you (or anyone here) can recommend for further reading about the science behind the elements a plant needs to grow?

lathyrus_long 5y ago
"Soilless Culture: Theory and Practice" is a pretty good textbook. I also recommend the USDA's https://www.fs.usda.gov/treesearch/pubs/46345 https://www.fs.usda.gov/treesearch/pubs/46345 That's not about hydroponics, but the theory behind sophisticated growing in containers of soil-like potting mix is almost the same.

lathyrus_long 5y ago

I've been growing hydroponically through the pandemic. I'm now switching from commercial pre-blended nutrients to my own design, customized for my hard water and blended from individual salts. In the linked article, I briefly review the biochemistry, show the fertilizer design calculations using an open-source tool that I wrote, and review a lab analysis of the final solution. This is a fair amount of work, and I'd guess that relatively few non-professional growers would bother. I hope this may be interesting to anyone generally curious about plant nutrition though, or about the design of modern complete chemical fertilizers.

holonomically 5y ago
Very cool. Thanks for putting this together.
dkarp 5y ago
Very cool. Do you have any pictures of the full hydroponic setup (with plants)?
- itsgrimetime 5y ago
  also interested in seeing pictures/diagrams of the setup
- lathyrus_long 5y ago
  There's one in my post about the automation system, at: https://old.reddit.com/r/Hydroponics/comments/o8j68n/singleboard_automated_phecdosingmore_seeking_devs/ https://old.reddit.com/r/Hydroponics/comments/o8j68n/singleb... That was still with the old commercially-blended nutrients, though. I've so far used my custom blend only for a few bok choy, as a final quality control check since they're fast-growing. If those continue to look good, then I'll move my entire balcony to the custom blend in about a month.
  - jcims 5y ago
    Regarding the automation, I built a DIY closed loop distillation process with similar i/o requirements. I have nowhere near the skill required to build a dedicated board but found that node-red running on raspberry pi using mqtt to talk to nodemcu running tasmota created an extremely extensible and modular platform. I’m running 8 thermocouples, two pumps, two flow meters, two load cells, current sensing coil and zero crossing ssr to chop current to a 6kw 240v heating element. With tasmota the little mcus are just kind of like legos and i just put them where the wiring is convenient and keep some spares. All of the i/o is dumb, the control loops are all on the node-red flowgraph allowing for lots of visibility of terms when tuning pids. The node-red dashboard lets you mix telemetry and control on a very touch friendly format, and i spool all of it to influxdb to compare runs over time. I’m sure you’ve got what you need with what you’ve built but at a minimum node-red might be worth a look. I was suuuper impressed using it for this.

adriand 5y ago

What's insane to me is how much certain plants will grow in tap water with zero regard for their nutritional requirements. I frequently propagate houseplants by putting cuttings in a glass of water and sometimes I get lazy and don't re-pot them for weeks or even months. And they will often grow very well - shooting out tons of roots but also additional leaves and stems.

GhettoComputers 5y ago
That’s the same as saying there are animals that have more biological fitness (mice) than others (pandas). Carbon and nitrogen come from the air, water will hydrate them, but most plants have expectations. Orchids for instance can be artificially bloomed with phosphorus but if it was dormant people would just think it’s dying, as if natural cycles of less bloom was a failure of the plant’s growth!
soperj 5y ago
Bottoms of green onions to me are the weirdest. You can get multiple cuttings just from water.
- 71a54xd 5y ago
  Hard water is actually one of the worst things you can give to expensive house plants, distilled water is by far the best option to prevent root calcification and ph swings.
  - lathyrus_long 5y ago
    You can also acidify the water down to a reasonable pH, though even phosphoric acid is somewhat dangerous and the best choices (nitric or sulfuric) aren't something I want in my apartment. Amateur hydroponic growers often use reverse osmosis water, somewhat wasteful but cheaper than distilled. You can get RO systems designed for aquarium use with no pressure tank at the output and just let them slowly fill a barrel or tote, over hours or days.
  - soperj 5y ago

jazzyjackson 5y ago

I came by a book on "micro-propagation" once (getting diced up plant samples to root in a petri dish) - it discussed the old fashioned way to propagate orchids (once you have a mutation you like, you have to clone that one plant by however many you want to sell) - apparently coconut water was used as a nutrient medium. Found a source that discusses its use [0], apparently is has beneficial hormones as well, "Besides its nutritional role, coconut water also appears to have growth regulatory properties, e.g., cytokinin-type activity" [0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6255029/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6255029/

belval 5y ago

You know how sometimes you think about something and it appears out of nowhere the very next day? That's what this article is for me. I have been growing mint, basil, purple basil and rosemary in a custom NFT system for the last 5 months and I am starting to run low on my General Hydroponics nutrients which are somewhat expensive at ~100$ for the 3 solutions. This is very useful and I want to say a big thank you to the author for doing so much of the work I was planning to do!

polishdude20 5y ago
When you said NFT I got triggered. Then I realized this can't surely be the NFT I'm thinking about haha.
- belval 5y ago
  My bad, should've known better than to use NFT on HN. For those wondering, it stands for "Nutrient Film Technique" and it's basically running a small stream of nutrient solution in PVC tubes with your plants' roots being somewhat submerged. It's a pretty water-efficient technique, this link explains it well: https://www.trees.com/gardening-and-landscaping/nutrient-film-technique https://www.trees.com/gardening-and-landscaping/nutrient-fil...
  - cwkoss 5y ago
    Have you considered selling your Nutrient Film Technique on the blockchain?

DaftDank 5y ago

It takes a lot of patience, and good IPM, but living soil has been awesome to me. We often say we grow soil, rather than plants, because of the fact a healthy living soil will provide all the nutrients the plant needs, and all you have to do is water essentially. Speaking strictly from a marijuana perspective (the limit of my experience with living soil), it makes the marijuana taste better and have a better smell. I've seen two different growers, starting with the same clones from the same mother planet, where one grows in soil using bottled nutes, and the other does living soil. The living soil definitely was superior. With that said, living soil is not practical for everyone. Trying to do it indoors where you also live could create issues if you do not have a good IPM strategy, and fully understand the soil food web. "Teaming with Microbes" by Jeff Lowenfels is an excellent book to learn about how the soil food web works.

Baeocystin 5y ago
What do you do about spider mites?
- reydequeso 5y ago
  Sns217. Spider mites like it dry, so mist your plants and it may be a little wise to repot your plants or fertilize with cal/mag
sampo 5y ago
IPM = Integrated Pest Management
wefarrell 5y ago
So long growers are maximizing THC content and yield per area Hyrdo will outcompete organic soil. Personally I grow organic because I too prefer the taste and I really enjoy composting. However having grown in hydro I can tell you that plants grow bigger, faster, and more potent.
- dr-detroit 5y ago
  By soil you mean cocoa right?

intrasight 5y ago

It's "what molecules" a better phrasing?

lathyrus_long 5y ago
"What ions", strictly--they're salts, so they dissociate when they dissolve. But it's conventional to look at the breakdown by element, not by ion, even in cases where the specific ion is important. For example, fertilizers give "percent nitrogen from nitrate" and "percent nitrogen from ammonium", not "percent nitrate" or "percent ammonium".

bastardoperator 5y ago

Outside of light, nitrogen (N), phosphorus (P), and potassium (K), or NPK for short Finding the right combination of these elements is what hydroponics farmers do everyday, pushing the limits of their crop for maximum quality/yield. We are starting to see a big shift in hydroponic fertilizers from liquid to powder since nobody wants to pay for shipping water. I highly recommend https://github.com/kizniche/Mycodo https://github.com/kizniche/Mycodo for anyone doing anything in hydroponics.

zuminator 5y ago
The article lists 16 required elements: C, H, O, N, P, K, Ca, Mg, S, Fe, Cu, Mn, Zn, B, Mo, Cl.
- amelius 5y ago
  In what forms?
- onecommentman 5y ago
  As do most other websites like https://agrilifeextension.tamu.edu/library/gardening/essential-nutrients-for-plants/ https://agrilifeextension.tamu.edu/library/gardening/essenti... Interestingly none of the critical semiconductor elements are required by plants: Silicon, Germanium, Gallium, Tin, Gold, Silver…
Radim 5y ago
> Outside of light, nitrogen (N), phosphorus (P), and potassium (K), or NPK for short Ehm. Check out this Nature article on the importance of Carbon: https://www.nature.com/scitable/knowledge/library/effects-of-rising-atmospheric-concentrations-of-carbon-13254108/ https://www.nature.com/scitable/knowledge/library/effects-of... Very readable and worth reading in full. Especially the effects of elevated CO₂ on the C₃/C₄ photosynthetic pathway and crop yields.
- bshipp 5y ago
  Hydroponic growers are intimately aware of the need and benefits accruing from elevated CO2. You'd be hard pressed to find a greenhouse vegetable farm without a huge CO2 tank outside, as well as the technology used inside the scrub carbon dioxide from natural gas exhaust and reroute it into the plants. They tend to burn the natural gas during the day to feed the plants while storing the heat in huge water tanks to warm facilities at night. The primary constraint is maintaining low enough CO2 levels to remain healthy for the humans that work inside the greenhouse. Plants themselves can handle very high levels of carbon dioxide.

beebeepka 5y ago

This reminds me. In my layman's mind, having agriculture right next to roads is bad because vehicles are dirty. Recently, someone told that's not the case because "plants need this stuff". Any truth to that claim? I'm yet to read the article

intrasight 5y ago
Plants for sure absorb things they don't need, and that are toxic to themselves and to us.
boldslogan 5y ago
My childhood experiment actually comes in handy! I can confirm at the least that planting half of the same batch of seeds close to a road's (the tarmac's) edge next to it, and in a forest, my grass seeds grew much worse next to the road. Also I was told to never eat berries growing from a bush close to a road since they are more dirty.
godDLL 5y ago
Roads used to be full of gasoline drip, heavy metals from exhaust and such. Plants would suffer but absorb it and pass it on to you if you eat them. Nowadays not so much. Specifically around 200 times less so. Not worth consideration. Whatever comes from the road is usually baked by the sun, so no nutrients left there. No need for that. I can't come up with another way of analysis for this claim without it being more specific, but generally, no, that's not working today.

spaetzleesser 5y ago

Brawndo has what plants crave. It’s got electrolytes Idiocracy

dangerboysteve 5y ago
This was the very thing thing which came to mind when I read the title.
outworlder 5y ago
They weren't even wrong. I would totally buy a Brawndo hydroponic formulation.
- aaron_m04 5y ago
  The problem in Idiocracy was evaporation concentrating the ions until there was eventually too much for the plants to grow. I'm not sure what the solution is on real farms.

GhettoComputers 5y ago

Great post! This reminds me a lot of making dog food for people (aka Soylent) with the best profile, requirements, and because plants don’t complain about taste, you’ll have no problem with ratios! The only issue is about the effects of these elements and what they can do to the water or your home. Would they need a special environment to prevent fungi, algae, bacteria or mold that would also feast upon these nutrients? You said bacteria didn’t always appear but what if some will grow on hydro? What optimizations would you do for preventing infections?

lathyrus_long 5y ago
Some growers keep their reservoir and root zone as sterile as possible, using additives like hydrogen peroxide or calcium hypochlorite. Others dose beneficial bacteria intended to outcompete bad stuff, like Bacillus amyloliquefaciens (Hydroguard, Southern Ag Garden Friendly Fungicide). Algae can use the same nutrients as the plants, but can often be controlled by excluding light. Other bad microbes are generally heterotrophs, so they're feeding on something else (like dead algae or dead roots).
- GhettoComputers 5y ago
  Is it possible to make an ecosystem that is beneficial, like kombucha in a way? Will they be using indoor lighting like from weed grow LEDs (red and blue) or you planning all/mostly natural lighting? This is a really cool project, do you have any plans with plant hormones? I only know I used rooting powder, this article is interesting! I used ethylene as well to ripen foods with bananas but I didn’t actually use them on my plants. https://untamedscience.com/biology/plants/plant-growth-hormones/ https://untamedscience.com/biology/plants/plant-growth-hormo...
  - lathyrus_long 5y ago
    I grow mostly by sunlight on my balcony. I've also got some white LM301B lights, which seem very popular among those growing by artificial light only. Greenhouse growers supplementing sunlight still seem to prefer red-blue. You could tell a story like "some intermediate wavelengths will improve yield, and you can get them either from white LEDs or from the sun", though I'm not sure how rigorous the evidence is for that. I don't think there's much about plant hormone use that's specific to hydroponics. People use rooting hormone and foliar sprays of plant growth regulators and such, but they do that in soil too.

kortex 5y ago

> Sulfuric acid or nitric acid would have a more favorable effect on the nutrient profile, but they're more and much more dangerous respectively. Sulfuric acid is not really that dangerous unless you are getting the high test stuff from a chemical supplier. You can use battery acid refill solution, it's just deionized water and H2SO4 at around 30% concentration. That's mild enough that it won't cause any immediate burns, but you should still wear gloves and goggles when handling it. There's no need for nitric acid, since you are already supplying nitrate ions.

lathyrus_long 5y ago
Yeah, battery acid is sometimes used, and not a terrible corrosive risk with the precautions you note. I don't love that it doesn't come with any specs e.g. on heavy metal contaminants, but I think it's near-certainly fine in practice. ACS grade would have specs, but I don't want to handle the concentrated acid. Sulfuric acid would give me excess sulfate, but since the plants aren't too sensitive to that I expect that would be an improvement over my current excess phosphate. I'm not sure if I'd get calcium sulfate precipitation as the reservoir concentrated. Nitric acid would let me hit my target profile exactly (with a corresponding decrease in nitrate salts), but it's way more dangerous. I've seen nitric acid used in academic trials and in countries with weaker safety laws, but not commercially in the USA.
- kortex 5y ago
  Yeah, it's annoying there is no purity spec on the battery acid, but in all likelihood, it's pretty pure. One could always test it. I mean I bet nitric acid would work great for that purpose, it's just a bit more expensive and harder to get in some places, as you mention. It's definitely commercially available in the USA though. Duda diesel has it: https://www.dudadiesel.com/search.php?query=nitric https://www.dudadiesel.com/search.php?query=nitric Duda also has sulfuric which is likely higher purity, but you seemed to express some concerns about working with corrosives. I'm a former chemist, so anything short of super angry chemicals like piranha solution, I'm not too phased :D

comrh 5y ago

Really nice documentation, well done.

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julienfr112 5y ago

Does someone have a system with arduino and concentration probe that match every nutriment individualy with it's exact optimal concentration ?

flyingfences 5y ago
I've looked into exactly that sort of setup for a previous job a few years ago and the problem is that these probes don't exist for every nutrient and the ones that do exist tend to be very expensive. It wouldn't be a cost-effective apparatus unless it was set up with one probe station metering the outflow to the whole of an industrial-scale greenhouse.

serverholic 5y ago

Question: How do we know that we are giving plants everything "we" need? We get nutrition through the food we eat and there are many, many molecules that contribute to our health. This project is cool but I worry about subtle nutritional deficiencies if this food ends up being the majority of a diet. I have the same worry when it comes to lab-grown meat.

pjc50 5y ago
An obvious question would be selenium; RDA is about 50 micrograms, and the upper "safe limit" is 400 micrograms. https://www.webmd.com/a-to-z-guides/supplement-guide-selenium https://www.webmd.com/a-to-z-guides/supplement-guide-seleniu... That's an extremely trace mineral.
outworlder 5y ago
Where would the plants store useless (to them) elements and for what purpose?
- Djrhfbfnsks 5y ago
  I don't know the biology, so I can't answer specifically, but surely there are many cases of "useless" and even detrimental elements being stored in living bodies. Just look at heavy metal accumulation in animals for example.
- serverholic 5y ago
  Water in the plant, cells, really anywhere. Same thing happens when we eat or drink something. Various molecules enter our blood, organs, etc.
heurist 5y ago
I work in hydroponic farming. If you live in the US then the produce you find in a grocery store has been grown and harvested in severely suboptimal conditions for human nutrition. Outcomes will vary across hydroponic systems but you will see in a few years that produce grown hydroponically under natural light 1) has higher nutritional density, 2) tastes better, 3) has a longer shelf life. Much of this is due to being harvested when the plant is ready and transported relatively short distances rather being harvested early for multi-week cold chain transport.

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stevespang 5y ago

professional degreed horticulturist here: 1) grinding your own ferts is nonsense, JR Peters makes the best, hands down. 2) I built my own RO system with permeate pump years ago for like $350 in parts off the internet, uses pressure bladder tank and solenoid on timer (dumps every 45 min or so) to fill a 55 gallon barrel every 24 hours. I use the largest ice maker hexametaphosphate cartridge filters to control the calcium and keep it soluble so it will not poison the RO membranes,I get about 20 days on each hexmetaphosphate filter cartridge. Ph control is done with sulfuric acid from Duda Diesel, 1/2 capful in 55 gallons of plain city water (not needed for RO water) - - comes out to about 6.5 after 24 hours. My water is in limestone country, about 450 ppm soluble salts. Duda used to sell the real deal,it was syrup like and super dangerous, now it's watered down crap, still it will burn you real fast. Always wear gloves, full face mask and apron. You can also use weak battery acid from auto parts store, weaker. Many orchid growers use more expensive citric acid, they keep it mixed in concentrate tank for days,they are not loosing it's strength in hours as you suggest.

flightless 5y ago

Great stuff. I was thinking about this after watching a talk by the Beyond Meat CEO in which he states that instead of using animals to rearrange plant proteins into animal proteins (muscles), they're taking the animal out of the equation. My next thought was, can't you take the plant out of the equation too? How difficult is it to rearrange these nutrients from a fertilizer mix straight into something resembling animal proteins (though easier for humans to digest)? I wonder at what point plants scale better than raw conversion of fertilizer to whatever protein these companies seem to be synthesizing.

lappa 5y ago

Interesting but I feel like I'm still missing an important piece of information to use this tool. Is there a resource which provides optimal nutrient ratios for different plants?

sydthrowaway 5y ago

Can this be used to feed a family apartment

tanbog5 5y ago

But how can anything grow without the most important thing: Love.

godDLL 5y ago
That's this man's expression of love for his crop right there, what are you talking about, you insensitive dolt.