5 ms·

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 an

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.
    - uhhyeahdude 5y ago
      That seems like a perfect use of node-red. Your setup sounds pragmatic and effective; I’m sure there would be an audience for some kind of write up with diagrams, especially if it also functions as a node-red tutorial (of sorts). I know that I am regularly designing control systems for hobbyist ag setups, and I pretty quickly hit a wall due to having minimal coding background. Something like node-red seems really useful for someone in my situation. Thanks for the ideas!
      - jcims 5y ago
        It really makes the most out of the flow-programming paradigm and the integrated UI bits are really convenient. The architecture is pretty straightforward. MQTT over wifi acts as a message bus between node-red and your 'legos'. (You don't really even need a raspberry pi, you just need to be able to run node-red, an mqtt broker and have wifi. I ran everything from containers on raspberry pi and ran the pi in AP mode which kept everything self-contained and tidy.) For the i/o 'legos', i had more luck with the esp8266 than esp32's on Tasmota, but things have probably improved since then. You could also look at espurna, esphome, home assistant, etc. Main thing to look for is a firmware that supports some kind of async messaging protocol that nodered supports and has the i/o you need. You can buy a six pack of nodemcu esp8266's for $20 off amazon. Good luck and have fun!
  - dkarp 5y ago
    The tomato plant is huge! It seems quite foliage heavy though, do you think that's because of the commercial nutrient blend you used? Have you also looked at modifying the recipe at different stages i.e. during growth, flowering, ripening? What climate zone are you in (if you don't mind me asking)? I'll be growing a bunch of things in Spring and would like to make a setup like this. I'll keep an eye on the project and likely contribute if you're open to it
    - lathyrus_long 5y ago
      > It seems quite foliage heavy though, do you think that's because of the commercial nutrient blend you used? Mostly inadequate pruning, I think--I was planning to replace it soon, so I'd gotten lazy. Normally I remove side shoots and lower leaves, for less foliage and better yield. The fertilizer was Masterblend 4-18-38, which is intended for tomatoes and pretty close to the University of Florida's "Stage 5" tomato profile (per their article linked from my calculator). So I'd guess the nutrient profile was close to optimal, except for all the excess phosphate from my pH down. I'm on a somewhat protected balcony in San Jose, USDA Zone 9B. That's warm enough that I can grow tomatoes through the whole winter, as long as it's a cold-tolerant cultivar (e.g. Early Girl; or Sub-Arctic Plenty, which is a determinate so needs less/no pruning), and lots of other stuff too. And contributions definitely welcomed, especially on the controller firmware. That's currently in a state that's useful only to programmers. More work there (integration with home automation software, a nice browser-based interface to schedule irrigation and dosing, etc.) would make that accessible to a lot more people.
belval 5y ago
Impressive work! I had a couple of questions. - How do you find the best concentration for each nutrients for a given plant? I usually just make general-purpose mix with General Hydro but I see that your calculator includes some presets for specific plants. - I see that your board includes pH and EC probes. I always wanted those in my setup but I've read that they tend to degrade fast. In your experience is that true? - Where did you get the potassium nitrate? I always wanted to make my own mix but I've heard that buying large amounts online will put you on a list as it's a strong oxidizer (you can make explosives with it).
- 34679 5y ago
  Not OP, but I can give an answer to the first question. It starts with simply observing the plants. You can vary the dosage from crop to crop or between plants in the same crop. Plants with leaf tip burn will generally have too high of a concentration and plants with pale leaves will generally not have enough nutrients. This assumes other factors like pH are correct. Another option is leaf/flower/fruit analysis. For example, if you're growing spinach, you may view iron content as an indicator of quality, healthy plants. Determining the iron content of the leaves from plants dosed at different rates will help zero in on the optimum fertilizer program. The best way, IMO, is to test the nutrient solution before and after it has been "fed" to the plants. This requires a recirculating system for best accuracy, but runoff can also be collected in a drain to waist system. As the author mentioned, unused nutrients will build up in the solution. An ideal solution will have the nutrients used by the plants at the same ratio they are found in the virgin solution. Any skew from that over time will indicate which concentrations should be adjusted and by how much. It can be a tricky beast, however, as the uptake rate of any individual nutrient is influenced by the presence of other nutrients. Change one and you may create an imbalance elsewhere. Like most things, it's a process.
  - belval 5y ago
    That last part is interesting to me, how would you test the nutrient solution after circulating? Would you just pay a lab to run the analysis on what's left or evaporate the solution to increase concentration and then try to precipitate the ions left in the solution and weight those?
noud 5y ago
Very cool project! Do you know if there are any benefits of growing hydroponically compared to the conventional (farming) methods? Is it economically interesting? Is it more sustainable?
- smileysteve 5y ago
  Uses 5% of the water (few losses to evaporation) Time to harvest is typically 2-3x less / faster. Yields are 2-3x in volume (targeted nutrients, more hours of "sun") Can grow small without a yard (ie Condo, Apartment, Townhouse) (https://www.trees.com/gardening-and-landscaping/advantages-disadvantages-of-hydroponics# https://www.trees.com/gardening-and-landscaping/advantages-d...)
  - smileysteve 5y ago
    Much less interesting than this formula, but I grow with an Aerogarden. Takes ~2 weeks to 1st Harvest, lives on a bookshelf in my living room, 6 plants produce a salad for 2 about 1x a week. Lettuce is flavorful. I expect a single "planting" to last about 4 months (having done this a few times) In comparison to my outdoor winter crops (including Kale and Broccoli) , all planted around October 7th; Outdoor Kale and Broccoli aren't to first Harvest yet (estimated ~60 days)
    - noud 5y ago
      Very clear, thanks!
drewnoakes 5y ago
I'm curious to know how stable the blend of elements in tap water is. Do you have any data around this? I once used an inexpensive electrical TDS meter (total dissolved solids) to track the amount of non-organic solids in water both before and after filtering over time. My goal was to determine the rate at which to replace the filter, and it turned out the manufacturer's recommendation was perfect. However I did notice that the unfiltered water's measurement fluctuated a lot over time. Could that pose a challenge in your scenario? Thanks for a great read, btw.
- lathyrus_long 5y ago
  I have a drain-to-waste system running open loop, with a constant dose of acid and sensors monitoring the pH of the leachate that drains from the pots. In that system, I've seen step changes in that pH that I believe correspond to step changes in my source water, perhaps when my utility changes which wells supply me. Hard to say without a detailed water analysis, but I'd guess the changes in nutrient profile (e.g., ppm Ca) aren't too important, and that as long as I adjust the acid dosing to maintain target pH the plants won't be affected much. A single well may also show gradual seasonality, like from snowmelt and such. I assume that's happening too, but in my current setup that would be hard to distinguish from gradual pH variation due to changes in the plant nutrient uptake.
  - chana_masala 5y ago
    Wow, do you have more resources for the drain to waste system?
    - lathyrus_long 5y ago
      Nothing exciting--the plants drain into a 1020 tray, and a pump sucks up the leachate. The pump feeds into a waste bucket, through a sample cup that contains pH and EC electrodes. (It would be more common for the leachate just to drain by gravity, but the pumps made best use of my limited balcony space.)
indiv0 5y ago
If you got a reverse osmosis filter and thereby worked with neutral water as a starting point, would it be easier to achieve your target ratios? You wouldn't have to account for existing concentrations in the tap water. Also, I was under the impression that there are two stages for plant growth: vegetation and fruiting. The two stages have different requirements for nutrients: - high nitrogen, mid phosphorus, low potassium; and - low nitrogen, mid-high phosphorus, super high potassium respectively. Do you use the same mixture for both stages?
- lathyrus_long 5y ago
  Reverse osmosis water solves a lot of problems. Household RO systems are pretty wasteful, though; the pressure across the membrane is just the household water pressure, so the ratio of waste:purified is around 3:1. Fancier RO systems with pumps achieve higher pressure, and thus more favorable waste ratio. Those professional systems are way too big for me, but perhaps I could build something. I believe that professionally, RO isn't used to solve excess calcium, carbonate, sulfate, etc., since it's cheaper just to neutralize the carbonate with acid and adjust the fertilizer salts appropriately. RO is used to solve excess sodium, chloride, etc., since the source water is already above the final desired concentrations. I'm running a single nutrient profile for all my plants, regardless of life stage--I can scale all the element concentrations together, but I can't adjust the ratios. My yields would be better if I adjusted as you say, though. At some point I should add a third fertilizer part and dosing pump.

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.
  - uhhyeahdude 5y ago
    That seems like a perfect use of node-red. Your setup sounds pragmatic and effective; I’m sure there would be an audience for some kind of write up with diagrams, especially if it also functions as a node-red tutorial (of sorts). I know that I am regularly designing control systems for hobbyist ag setups, and I pretty quickly hit a wall due to having minimal coding background. Something like node-red seems really useful for someone in my situation. Thanks for the ideas!
    - jcims 5y ago
      It really makes the most out of the flow-programming paradigm and the integrated UI bits are really convenient. The architecture is pretty straightforward. MQTT over wifi acts as a message bus between node-red and your 'legos'. (You don't really even need a raspberry pi, you just need to be able to run node-red, an mqtt broker and have wifi. I ran everything from containers on raspberry pi and ran the pi in AP mode which kept everything self-contained and tidy.) For the i/o 'legos', i had more luck with the esp8266 than esp32's on Tasmota, but things have probably improved since then. You could also look at espurna, esphome, home assistant, etc. Main thing to look for is a firmware that supports some kind of async messaging protocol that nodered supports and has the i/o you need. You can buy a six pack of nodemcu esp8266's for $20 off amazon. Good luck and have fun!
- dkarp 5y ago
  The tomato plant is huge! It seems quite foliage heavy though, do you think that's because of the commercial nutrient blend you used? Have you also looked at modifying the recipe at different stages i.e. during growth, flowering, ripening? What climate zone are you in (if you don't mind me asking)? I'll be growing a bunch of things in Spring and would like to make a setup like this. I'll keep an eye on the project and likely contribute if you're open to it
  - lathyrus_long 5y ago
    > It seems quite foliage heavy though, do you think that's because of the commercial nutrient blend you used? Mostly inadequate pruning, I think--I was planning to replace it soon, so I'd gotten lazy. Normally I remove side shoots and lower leaves, for less foliage and better yield. The fertilizer was Masterblend 4-18-38, which is intended for tomatoes and pretty close to the University of Florida's "Stage 5" tomato profile (per their article linked from my calculator). So I'd guess the nutrient profile was close to optimal, except for all the excess phosphate from my pH down. I'm on a somewhat protected balcony in San Jose, USDA Zone 9B. That's warm enough that I can grow tomatoes through the whole winter, as long as it's a cold-tolerant cultivar (e.g. Early Girl; or Sub-Arctic Plenty, which is a determinate so needs less/no pruning), and lots of other stuff too. And contributions definitely welcomed, especially on the controller firmware. That's currently in a state that's useful only to programmers. More work there (integration with home automation software, a nice browser-based interface to schedule irrigation and dosing, etc.) would make that accessible to a lot more people.

belval 5y ago

Impressive work! I had a couple of questions. - How do you find the best concentration for each nutrients for a given plant? I usually just make general-purpose mix with General Hydro but I see that your calculator includes some presets for specific plants. - I see that your board includes pH and EC probes. I always wanted those in my setup but I've read that they tend to degrade fast. In your experience is that true? - Where did you get the potassium nitrate? I always wanted to make my own mix but I've heard that buying large amounts online will put you on a list as it's a strong oxidizer (you can make explosives with it).

34679 5y ago
Not OP, but I can give an answer to the first question. It starts with simply observing the plants. You can vary the dosage from crop to crop or between plants in the same crop. Plants with leaf tip burn will generally have too high of a concentration and plants with pale leaves will generally not have enough nutrients. This assumes other factors like pH are correct. Another option is leaf/flower/fruit analysis. For example, if you're growing spinach, you may view iron content as an indicator of quality, healthy plants. Determining the iron content of the leaves from plants dosed at different rates will help zero in on the optimum fertilizer program. The best way, IMO, is to test the nutrient solution before and after it has been "fed" to the plants. This requires a recirculating system for best accuracy, but runoff can also be collected in a drain to waist system. As the author mentioned, unused nutrients will build up in the solution. An ideal solution will have the nutrients used by the plants at the same ratio they are found in the virgin solution. Any skew from that over time will indicate which concentrations should be adjusted and by how much. It can be a tricky beast, however, as the uptake rate of any individual nutrient is influenced by the presence of other nutrients. Change one and you may create an imbalance elsewhere. Like most things, it's a process.
- belval 5y ago
  That last part is interesting to me, how would you test the nutrient solution after circulating? Would you just pay a lab to run the analysis on what's left or evaporate the solution to increase concentration and then try to precipitate the ions left in the solution and weight those?

noud 5y ago

Very cool project! Do you know if there are any benefits of growing hydroponically compared to the conventional (farming) methods? Is it economically interesting? Is it more sustainable?

smileysteve 5y ago
Uses 5% of the water (few losses to evaporation) Time to harvest is typically 2-3x less / faster. Yields are 2-3x in volume (targeted nutrients, more hours of "sun") Can grow small without a yard (ie Condo, Apartment, Townhouse) (https://www.trees.com/gardening-and-landscaping/advantages-disadvantages-of-hydroponics# https://www.trees.com/gardening-and-landscaping/advantages-d...)
- smileysteve 5y ago
  Much less interesting than this formula, but I grow with an Aerogarden. Takes ~2 weeks to 1st Harvest, lives on a bookshelf in my living room, 6 plants produce a salad for 2 about 1x a week. Lettuce is flavorful. I expect a single "planting" to last about 4 months (having done this a few times) In comparison to my outdoor winter crops (including Kale and Broccoli) , all planted around October 7th; Outdoor Kale and Broccoli aren't to first Harvest yet (estimated ~60 days)
  - noud 5y ago
    Very clear, thanks!

drewnoakes 5y ago

I'm curious to know how stable the blend of elements in tap water is. Do you have any data around this? I once used an inexpensive electrical TDS meter (total dissolved solids) to track the amount of non-organic solids in water both before and after filtering over time. My goal was to determine the rate at which to replace the filter, and it turned out the manufacturer's recommendation was perfect. However I did notice that the unfiltered water's measurement fluctuated a lot over time. Could that pose a challenge in your scenario? Thanks for a great read, btw.

lathyrus_long 5y ago
I have a drain-to-waste system running open loop, with a constant dose of acid and sensors monitoring the pH of the leachate that drains from the pots. In that system, I've seen step changes in that pH that I believe correspond to step changes in my source water, perhaps when my utility changes which wells supply me. Hard to say without a detailed water analysis, but I'd guess the changes in nutrient profile (e.g., ppm Ca) aren't too important, and that as long as I adjust the acid dosing to maintain target pH the plants won't be affected much. A single well may also show gradual seasonality, like from snowmelt and such. I assume that's happening too, but in my current setup that would be hard to distinguish from gradual pH variation due to changes in the plant nutrient uptake.
- chana_masala 5y ago
  Wow, do you have more resources for the drain to waste system?
  - lathyrus_long 5y ago
    Nothing exciting--the plants drain into a 1020 tray, and a pump sucks up the leachate. The pump feeds into a waste bucket, through a sample cup that contains pH and EC electrodes. (It would be more common for the leachate just to drain by gravity, but the pumps made best use of my limited balcony space.)

indiv0 5y ago

If you got a reverse osmosis filter and thereby worked with neutral water as a starting point, would it be easier to achieve your target ratios? You wouldn't have to account for existing concentrations in the tap water. Also, I was under the impression that there are two stages for plant growth: vegetation and fruiting. The two stages have different requirements for nutrients: - high nitrogen, mid phosphorus, low potassium; and - low nitrogen, mid-high phosphorus, super high potassium respectively. Do you use the same mixture for both stages?

lathyrus_long 5y ago
Reverse osmosis water solves a lot of problems. Household RO systems are pretty wasteful, though; the pressure across the membrane is just the household water pressure, so the ratio of waste:purified is around 3:1. Fancier RO systems with pumps achieve higher pressure, and thus more favorable waste ratio. Those professional systems are way too big for me, but perhaps I could build something. I believe that professionally, RO isn't used to solve excess calcium, carbonate, sulfate, etc., since it's cheaper just to neutralize the carbonate with acid and adjust the fertilizer salts appropriately. RO is used to solve excess sodium, chloride, etc., since the source water is already above the final desired concentrations. I'm running a single nutrient profile for all my plants, regardless of life stage--I can scale all the element concentrations together, but I can't adjust the ratios. My yields would be better if I adjusted as you say, though. At some point I should add a third fertilizer part and dosing pump.