Aquaponic Gardening

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Have had pretty good luck growing must things except root vegtables. Radishes are okay, but not great. Same with carrots. From growing in soil I know it takes the three main things to be balanced. Nitrogen, Potasium, and pot ash. Plus other things like Iron. In aquaponics, nitorgen usualy isn't an issue, due to what the fish provide in the water. plus I add Iron chelate occasionly. But what are the thoughts on adding potasium, and potash. If I rememeber, if pot ash is down, root vegitables do not do well. Of course then there's the thought is we start adding chemicals, we're not into "true" aquaponics, it's more like hydoponics. All thoughts and oppions welcome

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True root crops (not radish) require adequate pressure in the soil.  The root crop development occurs in response to turgid pressure on a cellular level.  The poor radish development is unlikely to be attributable to the medium, but for the carrot it may play a part in the poor root crop development.

Adam Vicknair said:

I thought the deal was that root veggies will grow in an AP system but will come out in wonky shapes because the media isn't as forgiving as soil is. So far I have tried radishes and they didn't do anything. They sprouted then yellowed and stunted as wee sprouts for the last couple of months. I believe that it is because my system is young and has not developed the P or K concentration needed (like you say) for root vegetable growth. How old is your system? From what I remember reading Aquaponic Gardening your system needs to be something like six or eight months old before it has the right concentrations of nutrients to grow anything other than leafy greens.

Morton claims on their product site that that particular product contains no additives or binders, so if that's true it should be a good candidate Mike.

Mike Roe said:

My intention was to help the poster avoid the bad advice given.  You seem smart; so, I assumed you would find the information on your own. For instance, the monovalent cation K (+) will strongly compete with Na(+) for uptake.  Likewise, the divalent cation Ca (2+) will compete with Mg (2+).  The activity of a particular ion (which is what appeared to be what you were attempting to discuss) as it is affected by other concentrations, pH, etc. is not the reason for the poor root development.  It was stated that Nitrogen was plentiful and in excess in the system.  The ratio of the N-P-K influence plant growth regulators that inhibit or promote different areas of a plants development.  In this particular case given the poor pH for P bioavailability (below 6.5 / above 7.5), P becomes other chemical species that are not bioavailable or flat out precipitates out of the soil solution.  The plant's "symptoms" would suggest either an increase in P or a decrease in N is required.  Since adding things to a sustainable system goes against the very idea of sustainability, the only logical choice is indeed to lower the N in relation to P and K.  So yes, plant your growbed out properly so the available nutrients come into a perfect balance with the waste from the fish AS OPPOSED TO DUMPING POUNDS OF INORGANIC CHEMICALS INTO AN IMBALANCED SYSTEM.

You have several other glaring mistakes and omissions in your post.  I'm not going to read everything over again just to point out all the flaws, but the most painful mistake I noticed was you blindly gave advice to add KCl to a system.  The amount you suggested adding was far beyond the amount required for proper root development for carrots (I checked 2 references at my fingertips) and the worst part is this much KCl will kill MOST species of cultured freshwater fish.  Potential dangers from osmotic shock to the fish from dumping pounds of salt into a system raise concerns as well.

See how much more I had to type and how much more time it takes to reply?  My post here will NOT replace an education that affords you a sound understanding of some basic scientific principles involved in understanding aquaponic systems.  Most people don't enjoy posting arithmetic computations of stoichiometric quantities to help people online.  Obviously, you have a passion for this stuff, but you have large gaps in your knowledge.  There's nothing wrong with that.  You are beautiful! :-)  Just keep on learning, but be mindful that your suggestions could kill off someones fish or take food off someone's table.  My apologies if I've assumed wrong, maybe you two are close friends and you know it's safe to give bad advice to this poor fellow.  If you want I can point you towards many, many free online resources for some of these type of undergraduate topics.  I did not mean to drag us into a meaningless debate about how you were wrong, but rather I wanted to simply avoid the harm to the poster regarding the bad advice and possibly incite you to fill in your gaps in knowledge.  We all have them, but if we don't know then we're left to assume.  :-)

Perhaps my unusual sense of humor was misunderstood, but I still contend the following: 2 much N


Vlad Jovanovic said:

Right Izzy. You caught me. I'm just making this stuff up...

"The crux of the issue" is Mike's stated need to add some plant essential elements (in this case K) in a manner that will not affect his pH.

Selective permeability doesn't mean much when there's not enough in solution to 'select' or 'permeate'.

And what would you have Mike do? Take out some fish to lower N...Or perhaps add more plants to use up some of those nitrates? Neither seem like a particularly useful strategy. I fully stand behind everything I've said about increasing the amount of K which is present in solution as a remedy. 

Please enlighten me on my "seem(ing) to misunderstand the interaction between divalent cations and monovalent cations competing for uptake to plant roots capable of selective permeability, especially given the pH conditions." as it pertains to the OP, or anything that I've stated here. It will save me a trip to the 'local community college'.

Izzy, did your community college professor tell you that crap, or did you just now Google it? 

It seems I have overestimated your intellect.  What can you learn with that kind of attitude?  It's unfortunate you insist on remaining a layman on a subject you clearly are passionate about.  For shame!

Vlad Jovanovic said:

Izzy, did your community college professor tell you that crap, or did you just now Google it? 

Good God why all this crap between two people, I do appreciate everyone's opionon but this is getting out of hand, 

No, seriously have you ever actually tried any of those things in any of your systems to see for yourself how they pan out?

I'm not really sure what he's after.  I presented a sound enough argument backed by simple scientific principles to no avail.  Oh well, it's the Internet and it happens.  I hope my curiosity about this guy doesn't backfire.  I'm just waiting for him to calm down and respond intelligently.  Maybe we BOTH can learn something, God willing.  :-)

Mike Roe said:

Good God why all this crap between two people, I do appreciate everyone's opionon but this is getting out of hand, 

You require anectdotal evidence instead of reproducible scientific evidence?  Interesting.  (just messing with ya)  ;-)

And yes, I have grown several radishes and carrots.  Every year I take a picture of my largest radish as tradition.  So far, I have gotten round globe radish to a size larger than my foot and short white icle top radish to a size larger than a human head!  I have not tried the large Daikon radish, but I intend to this year.  I do not add any K to my system.  The only thing I have ever added to MY PERSONAL system is iron.  However, I have added KCl to large commercial systems I have consulted on.  Production is very important for these kinds of systems; so, I compromise on the sustainability.

As a side note, I truly wish I did not have to add anything to my system, but if you have ever done thermokinetic calculations on iron interactions in soil solutions you will understand just how hard it is to maintain adequate iron levels in a recirculating system such as these.

P.S. I may have gotten the name wrong on the radish varieties.  I save my seed for next season and I don't remember what it said on the package from when I bought them many years ago.

Vlad Jovanovic said:

No, seriously have you ever actually tried any of those things in any of your systems to see for yourself how they pan out?

Well, both types are usually nice as recently I've found a host of things that "should not have been" according to accepted textbook literature (both temp and pH related). So yes, I like a good dose of firsthand anecdotal evidence to go with what the papers say.

These last six months or so, I've been reclaiming biological phosphates (from urine) in the form of MAP/Struvite crystals (NH4MgPO4·6H2O) . The effluent by-product left over from the process is very K rich and seems to be a resource unto itself...So I've been playing with it/testing it in some of these smaller systems. What I'm seeing is that adding this K rich effluent to some of these bio-ponic systems (since the NH4 source is either the MAP, or straight humonia...they are thin in the K department) will apparently alleviate the K situation even though NO3- is quite high (140 to 160 mg /L). Which is why I do not prescribe to your textbook suggestion of lowering N as the only possible solution in all such a situations. Adding such effluent to a system with fish would produce an ammonia spike, Hence the KCl and hand picked sea salt for TE's. I wouldn't use MaxiCrop on the basis of it's heavy metal content alone. (Also, I think that all those extra auxins and cytokinins were responsible for some pretty unruly-ness exhibited by my toms i.e fruit clusters not knowing when to terminate....

Although I love AP, I certainly do not count it as a "sustainable" method of food production even when practiced in it's "purist" form. So I see nothing wrong with adding a compound(s) mined from the Earth, or picked off the rocks by the sea, or made from my own urine, or from the ashes of hardwood trees that I heat my home with etc...

Look it's almost 3:00am here, and I've got a long day ahead of me (teaching my fish that they are supposed to be dead ;) I take it the KCl additions for you client did not (as your quick fingertip search suggested) result in a massive fish kill?

We can slug it out some more tomorrow or whenever. It's way past my bedtime and my head already isn't working properly. (Though this is interesting, really... thanks). 

Sorry about the "Google" wise crack, but you started it ;) (Sorta caught me at I bad time...I do apologize  We should tone it down a bit and not freak the other guys out.

Apology accepted! :-)

Well, I can't quite agree with strip mining the Earth to source inorganic compounds that we can source locally and sustainably (like from urine, awesome)! 

I'm not 100% positive, but I believe the Chinese did just that thousands of years ago.  I even think they are practicing similar concepts even today in a very low-tech DIY style fashion we would all be proud of!

I think I understand your perspective now. I do not see the wealth of scientific knowledge to be in conflict with the spirit of innovation and research.  On the contrary, I think science compliments such endeavors.  I expect you will come to agree with me in time, but you will have to discover that on your own.  I once felt the same way you do, as do most who seek knowledge.

I did not mean to imply that was the ONLY solution (haha, a solution for the poor solution).  I have simply given these suggestions hundreds of times before (maybe thousands, seriously).  I automatically offer my advice in the context of backyard gardening and that most people are lazy gardeners (as I am, and proud of it).  However, I am an avid tinkerer and experimenter.  I am culturing a 10 gallon tank at higher temperatures with some urine and some selected microorganisms (aerated this time).  I have no idea what will happen, but I'm monitoring it and regularly performing microscopy.  It's probably a waste of time, but one such experiment yielded an effluent that was dark grey.  I wonder if it's similar to the effluent you have discovered?  It takes a while to decompose the urine and it's done with the assistance of what looks like a large fungal colony of TWO distinct species (one white, one black).  I didn't microscopy or assy the solution because I was scared to touch it even with gloves! LOL :-)

As far as the KCl, it will not kill Tilapia because tilapia have a chloride cell that acts as an osmotic pump for chloride ions in their blood serum (don't you just love the selective permeability of membranes :-).  It will kill other species though.  It's all relative.  I'm guessing you have Tilapia as do most aquapons?

I think we're a lot more alike than you first assumed! :-)  Don't worry, I knew from the stoichiometry in your post we were kindred.  There's a special place in my heart for biodegradation and bioremediation; so, I hope you share more about your pee sludge with us.  Send some to Mike, maybe you can trick him into testing it!  Oh crap, he can read this can't he? Sorry Mike!  ;-)

Wow, I was just browsing some seeds for a friend and I came across another solution to Mike's carrot problem.  How about we use a different cultivar of carrot!  This one "claims" to grow in gravel:

If that doesn't show, try to google or ebay/amazon search for "Carrot Parisian Seeds".

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