lathyrus_long

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.

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.

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.

You'd pay a lab about $45, same as I did for my quality control check. A few of the ions--like nitrate or ammonium--will probably get tested with some kind of color-change reaction, and quantified with a visible-light spectrophotometer. The rest will be from ICP (inductively coupled plasma), a precisely-quantified version of the same effect as where different elements make a flame turn different colors.

The nutrient profiles in my calculator are copied from various academic publications. Those profiles typically come with less discussion of how they were designed than I might hope, but I assume it's from review of trials of the form mentioned in the other reply to your comment. For more profiles, I've never used anything from

https://cdnmedia.eurofins.com/corporate-eurofins/media/12142...

but I suspect from the author's bio that it's trustworthy.

For probes, see

https://github.com/hydromisc/hydromisc/blob/master/doc/senso...

EC probes should last basically forever if correctly excited (zero net DC). pH probes are consumables, but my $10 probe is still happy after a year continuously immersed. As process fluids go, hydroponic solution is pretty mild, neutral-ish pH and decent ionic content.

I bought the potassium nitrate from MBFerts in combination with other fertilizer salts, so if I'm on a list it's probably "cannabis growers" and not "mad bombers". If you'd rather not use it, then a quick experiment in the calculator shows you can still hit a decent profile with just calcium and magnesium nitrates.

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).

"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".

> 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.

> 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.

> 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.

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.

I think that's not by accident. Typical houseplant species seem to be selected for their ability to look good with minimal fertility. That makes them easier to grow, but harder to grow optimally. For example, mint will quickly indicate any deficiency in its leaf appearance, but pothos / devil's ivy will mostly just grow slower.

There's one in my post about the automation system, at:

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.

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.

Here's an article on the technical challenges of a different treed building, Italy's Bosco Verticale:

https://global.ctbuh.org/resources/papers/download/2099-a-ne...

The weight of the soil and water isn't negligible, but it's not that bad. Most plants will grow happily in a tiny fraction of their root volume in nature, as long as precise irrigation delivers water (or fertilizer solution) just as it's needed. The practical root volume is probably chosen mostly based on the longest expected fault in the irrigation system.

The tiny root system also provides a very weak attachment to the building. Bosco Verticale strapped each tree to a vertical steel cable, plus various additional restraints.

As to the seeds, a reputable vendor isn't just starting with any random fruit. Even for an open-pollinated variety, you want large separation distances from other varieties to avoid unwanted cross-pollination, potentially miles. You can also grow indoors, but that's more expensive and requires hand-pollination or introduced pollinators. You also need more careful artificial selection (roguing), to avoid long-term degradation of the genetics.

For an F1 hybrid you need to do all this work to maintain each of the pure lines, and then also do the cross. Once you have the fruit, the seed needs to be separated, dried, perhaps tested for viral, bacterial, or fungal disease, perhaps treated with fungicide, and tested for germination.

Of course a random pumpkin seed will grow with some probability, and the resulting plant will bear some kind of pumpkin. But the cost of high-quality seed is a very small share of the total cost of growing a pumpkin, so it's not a good place to cut corners.

ETA: And the article notes explicitly that those seeds were hybrids. For emphasis, saving seeds from hybrids may or may not be legally permissible, depending on the patent status and any contracts signed, but with very few exceptions it doesn't work--the genetics aren't stable, and the F2 doesn't reliably have the same desirable traits as the F1.

It's helpful to learn and use professional terminology, to get away from heavily SEO'd search terms. A search for "when to water potted plant" returns endless variations of the same mediocre article, but "coir irrigation frequency" returns good stuff.

If you like aquaponics, then take a look at Goliad Farms. He raises greenhouses full of tropical fish, relying entirely on plants to remove ammonium from the water.

And yeah, that root zone microbiome is complex, though somewhat different in containers than in nature. In soil-like potting mix, you're generally guaranteed to have nitrifying bacteria, so ammonium fertilizers are still generally safe to use. (Ammonium can easily become toxic to plants; but soil bacteria oxidize it to nitrate, which plants tolerate in higher concentrations.) Stuff like sulfur to amend soil pH doesn't necessarily work in containers though, since you don't necessarily get the bacteria that oxidize that to sulfuric acid. Nitrogen-fixing bacteria for legumes may also not be present unless deliberately inoculated.

The plants would die without that microbiome in nature, but with human help it's not mandatory. Many hydroponic methods run with a root zone that's as sterile as possible, and the only major change required is to supply most (~90%) of the nitrogen as nitrate.

A study found that vinegar significantly slowed growth (vs. citric or phosphoric acid) in all three plant species tested:

https://sciendo.com/pdf/10.2478/johr-2019-0004

It may still be better than nothing, since they didn't test nothing. Citric acid was better than vinegar for them, but still showed worse yield than phosphoric. I tried citric acid myself and found that its pH down effect disappeared within hours, as some combination of the plant itself and the root zone microbiota broke down the citrate:

https://old.reddit.com/r/Hydroponics/comments/q4u5wz/gh_ph_d...

The professionals generally use mineral acids, and I believe that's with good reason. Of those phosphoric is the safest to handle, though a significant corrosive hazard in concentrated form; carefully dilute to ~2% for day to day use. You could also try monopotassium phosphate, but if your water is hard then you'd need such massive amounts that the extra K and P may become problematic.

They should be fertilized at the same rate at which the plants are consuming the fertilizer. Professionals will often judge this by measuring the electrical conductivity (EC) of the solution leaching from the bottom of the pot. The fertilizers are mostly ionic (excluding urea, though that becomes ionic after breakdown to ammonia), so that conductivity is roughly proportional to the root zone fertilizer concentration.

These meters used to be expensive, but you can get them for a few dollars on eBay, AliExpress, etc. now. Such measurement is now de rigeur in hydroponics. It works in soil-like potting mixes too, though only the most technically sophisticated hobbyists there (e.g., many orchidists) have adopted so far.

http://www.yieryitools.com/sale-9685340-high-accuracy-drinki...

I also found that advice about as confusing as all the other consumer-targeted houseplant advice. If you've got some time to invest, then I believe you'll find that advice for professional growers makes a lot more sense, much more quantitative and backed by trials and chemical or biological mechanisms. I quite like:

https://www.fs.usda.gov/treesearch/pubs/46345

That's a guide to operating a nursery, developed by academics seeking to distill the scientific state of the art into something practically useful with basic equipment.

Specifically as to judging how much to water, I go mostly by weight. Thoroughly wet the medium until water runs from the holes in the pot, and then don't water again until the weight drops below some fraction (e.g., 20%) of that maximum. You can use a scale, or judge by hand with practice.

You can also wait until the plants show drought stress. For example, they might visibly wilt, or succulent leaves and herbaceous stems may go from turgid to limp. That's probably not optimal, but it's better than overwatering.

Finally, you can also pot in media with very low water holding capacity, like a blend of normal potting mix and perlite. This makes it near-impossible to overwater, but the tradeoff is that frequent (e.g., every few days) watering then becomes mandatory.

Hypochlorite (like they add for disinfection) will break down on standing, or faster with aeration. Chloramine (also added for disinfection) won't, which is why aquarists use various chemical treatments to remove that.

Neither is too important for plants, though. The usual problem for plants is chloride, which can't be removed except by processes like reverse osmosis or distillation. Most plants can easily survive chloride at typical concentrations in tap water; but if you don't water to runoff then that concentration may slowly increase in the root zone, eventually harming the plant. You typically want something around 10% runoff, though that will vary with your plant species, water, fertilizer, etc.

Each utility should report water quality. For most of San Jose, it's

https://www.sjwater.com/sites/default/files/2021-06/ccr.pdf

The parameters relevant to plants (EC, pH, chloride, etc.) are usually in the secondary standards, rather than the primary standards most important for human health.

San Jose groundwater is terrible, EC ~ 700 uS/cm out of the tap. I wrote

https://hydromisc.github.io/hydromisc/doc/nutrient-calculato...

to model the custom fertilizer blend that I'm developing now, since the cal/mag in the water plus the phosphate from the acid I use to neutralize the carbonate significantly shift the nutrient profile. That's obviously beyond typical houseplant practice, but professionals growing in non-soil media (nurseries, vegetable growers, etc.) do roughly the same.

Beyond genetics and environment, soil/nutrient fertility also affects the taste. For example, drought-stressing tomatoes near harvest generally improves flavor at the cost of yield, both by the obvious mechanism of adding less water and by more complicated interactions with the biosynthesis of flavor compounds.

In hydroponics the same improvement is achieved by increasing the nutrient solution concentration (since that's what drought stress looks like to the roots), often literally with salt, NaCl. Growers will typically describe this as raising the solution electrical conductivity, EC, since that's an easily-measured proxy for total dissolved ionic stuff. Hand-held EC meters cost a few dollars, or large systems often run with closed-loop measurement and dosing similar to my

https://github.com/hydromisc/hydromisc

> A plant that keeps putting harmful substances in its fruits is losing the game at middle term. We would just spread more seeds of its tastier competitors instead.

Humans indeed find some endogenous pesticides unpleasant; but we enjoy others very much, to the point of addiction. For example, nicotine from tobacco dust was used historically as a pesticide on other plants, and many modern synthetic pesticides are nicotine analogs (neonics). On a milder note, the compounds that give many herbs their flavor are also insecticides--it's easier to grow basil without an aphid problem than lettuce. The question of why we evolved to enjoy those poisons is interesting, with no clear answer:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3817850/

That said, the original claim makes little sense. Natural pest resistance often arises from higher concentrations of endogenous pesticides, but this would generally just mean something like "stronger-tasting herbs", not any harm. Even if it were harmful, conventional growers prefer varieties with good natural resistance too.

The point is that if a product is twice as toxic to humans (or bees, or some other off-target species) but four times as toxic to the target pest, then the grower can use a quarter as much and the adverse impact is half. The relevant factor is that "therapeutic index", not toxicity per gram. By that standard some organic pesticides are better than the conventional average (e.g. azadirachtin), while others are worse (e.g. pyrethrin, or rotenone until it was banned).

Also, please don't take gardening advice from whatever website you're quoting. Sodium bicarbonate is not an effective insecticide. It's a marginally effective fungicide, though potassium bicarbonate would be less toxic to the plants. It's indeed pretty safe for humans, but the dose makes the poison even there and people have died from sodium bicarbonate overdose:

https://www.tandfonline.com/doi/full/10.1080/24734306.2020.1...

Unfortunately consumer gardening advice seems to be the domain of SEO specialists, not gardening specialists. University extension offices publish high-quality information with much less visibility, like:

https://www2.ipm.ucanr.edu/

Yeah, though with some interesting exceptions like Dutch orchid greenhouses. Foreign countries with cheap labor and suitable climates have a big natural advantage, but intensive scientific agriculture (to make best use of the expensive greenhouse space) and automation can apparently overcome that in some cases.

The Israelis invented modern drip irrigation and use it extensively. They also make good use of low-quality water, like treated wastewater and not-totally-desalinated seawater, by developing salt-tolerant varieties and carefully optimizing plant nutrition under their constraints.

Of course they do lots of hydroponics too, for the usual hydroponic crops (tomatoes, cucumbers, etc.). The science in hydroponics and science in sophisticated soil culture aren't really that different--you'll see mostly the same chemical fertilizers, the same EC and pH measurements in the field, the same lab analyses by ICP, etc.

Some water still drains to the aquifer and is "wasted". It needs to be though, or else unwanted ions (from impure source water or fertilizer, including but not limited to Na+ and Cl-) would accumulate and kill the plant. Israel has a significant problem with salinization of their soils and groundwater, and lots of interesting work modeling that.

Pesticides are still widely used indoors. Pests will get introduced even with strong precautions (air showers at the entrances, etc.). At that point, if they're able to multiply then they will, potentially even faster than outdoors since there are no natural predators. There also tends to be less airflow, which encourages pests like spider mites.

Of course the greenhouse has advantages too--you can deliberately introduce beneficial (predatory) insects and they can't fly away, and if you do end up using pesticides then there's no risk to wild pollinators. For example, the EU banned certain neonics outdoors but still permits indoor use. It's more just different than strictly easier or harder.

The list of pesticides allowable in organic farming is (at least under OMRI rules) determined by naturalness, not safety. For example, pyrethrin occurs naturally in chrysanthemums, so it's allowed, even though it's highly toxic to bees. Tau-fluvalinate is a synthetic pyrethroid (pyrethrin analog), so it's forbidden, even though it's sufficiently nontoxic to bees that it's used as a miticide in commercial hives.

Synthetic pesticides are designed and screened in the same way as small molecule drugs, a long and uncertain process that's still far easier than discovering a new natural product. At least in theory, these synthetic compounds can be optimized for whatever we want. It's just that absent regulation, the commercial incentive is for better short-term yield regardless of the ecological cost.

One could imagine a certification similar to organic that forbids the most ecologically damaging practices--even if they're using natural products--and permits safer use of synthetic products. Probably a hard sell to consumers, though. I've occasionally seen produce marketed as "IPM" (integrated pest management), which isn't quite that but goes in that general direction.