An ounce of Prevention..........

[Richard Kowalski]

Hello Aquaponics Gardeners,

My system is up and running for 2 months and doing well. 

I am growing Many different Vegetables in my system. Peppers, Melons, Tomato's, Broccoli, Lettuce, Egg Plant. Some plants are doing great and some plants not so great. I realize that each variety of plant has different needs to be able to grow well. I read some posts and downloaded Dr. Nate Storey's "Plant Deficiencies" guide. (Thanks Dr. Storey!)

We have all heard the adage "An Ounce of Prevention is worth a Pound of Cure".

 My question is for all of you experienced people out there. I have wondered if anyone uses some sort of regimen for adding Iron, Potasium, Calcium, etc. in order to be able prevent those deficiencies from happening in the first place. I am sure that you experienced people are not just growing one variety of vegetable in your gardens. I have been using alot of Potasium Bi Carbonate and Calcium Carbonate in the system to off set the natural tendency of the Ph going down. Is it possible to be adding too much of these compounds over time?

Thanks in advance for your replies!

[Alex Veidel]

While it currently hasn't kept me from needing the occasional supplement, I've been experimenting using worm compost extracts in my system water. It would be interesting to see if I can eventually eliminate the need to purchase additional nutrient salts....

[Richard Kowalski]

Alex,

Thats interesting. I wonder what kind of nutrients are in worm compost tea. I guess it would depend on what they were fed. 

[Vlad Jovanovic]

Yes Richard, it would depend on what they were fed. A while back my castings clocked in at

2.28%Ca and

1.85%Mg

1.73%K

1.43% N 

2%P ...and some TE's (trace elements)

Also, what will give the appearance of differing essential element value is the way in which people/companies are (still) allowed to calculate and label those said essential element values...meaning to say that it is still legal here in the US for companies to use the rather antiquated methods in order to artificially "boost" their numbers.

For example MKP (mono-potassium phosphate), a very common fertilizer is often labelled as containing 52% phosphorous, and 34% potassium. In reality though it contains only 22.7% phosphorous and only 28.7% potassium.

And this discrepancy between "what the label/marketing says" and "the reality is" is only made possible, because here it is still legal to calculate K as K2O...and P as P2O5. So that the numbers can be quite misleading.

Keep this in mind when reading N-P-K and other plant essential element contents of worm casting or any other fertilizer...

This may (or may not) explain some of the 5-5-5 numbers claimed on some bags of worm castings...they might just have some weird breed of super charged worms and/or feed  (not likely, but certainly possible. Though my un-educated guess is that the existing labeling loop-hole allows for some "fuzzy math" to legally be taken advantage of)...

[Alex Veidel]

Your castings, eh? What have YOU been eating to get such numbers? :D

Vlad Jovanovic said:

Yes Richard, it would depend on what they were fed. A while back my castings clocked in at

2.28%Ca and

1.85%Mg

1.73%K

1.43% N 

2%P ...and some TE's (trace elements)

[Alex Veidel]

The use of worm compost in aquaponics is actually going to be the subject of my presentation at Aquaponics Fest......nothing too comprehensive, but should be fun :) The main idea will really be just getting everybody thinking about plant nutrition and how we can begin to make nutrients more available to our plants.

[Vlad Jovanovic]

Hehe, the castings my worms made :)

[Richard Kowalski]

Vlad,
I have tomato's and egg plant in the same grow bed. The tomato plants do not show any sign of nutrient deficiency, however the egg plant has yellowing old growth. So I would see that as a nutrient deficiency for the egg plant.

Do you have a regimen that you use to add nutrients to your system in order to prevent any nutrient deficiencies across different plant species in the same growbed?

[Vlad Jovanovic]

Hi Richard,

Yes,buffering allows one to add needed nutrients while regulating pH...you can alternate (as you already are) your buffers. Throw in a magnesium buffer in there too, if your seeing inter-venal chlorosis on the older leaves. Magnesium carbonate (the chalk gymnasts use), or Dolomitic lime (which is about half calcium carbonate and half magnesium carbonate) would be good choices. 

Brand new (or cycling) systems are most prone to deficiencies, and can also be most prone to fish deaths due to nitrite toxicity...so salting (chloride salts) for fish health also affords one an opportunity to add some needed plant nutrients at the same time.

The chloride salting I generally only do once before I put fish into a system, since the mechanism by which chloride ions mitigate nitrite poisoning (called comparative inhibition) works preventatively and is not a "remedy" to employ while in the midst of a nitrite spike (by then it's pretty much too late for the salt to help your fish). 

And that's pretty much it. The one time salting for fish health....then just alternating (Ca, Mg, K) pH buffers...