What if you dose and your plants eat all nutrients so conductivity is near zero?

[PeerUnk]

Hi all,

What if you dose ferts and your plants eat all nutrients so conductivity is near zero?

I had such a case.

Last summer I dosed in an experiment a hydroponic solution in multiple dilutions in different jars with RO and added Phyllanthus fluitans aka RRF. After two week they looked healthy:
start: two weeks:

A couple of weeks more, some looked nitrogen starved. But measuring the conductivity, some were 2-3 uS/cm above their starting conductivity = 5 uS/cm.


Based on the fact they did well on the mix and almost consumed all conductivity, I got curious.
1. Could a vast range of plants grow healthy on these ratios?
2. And if so, there might be low buildup of nutrients looking at the remaining conductivity?
3. And if that's true, could I use conductivity to monitor the uptake and decide when to dose nutrients?
4. And as there is little buildup, could I run my tank healthy with little need for water changes?

Could this actually work?

 

[PeerUnk]

One might wander all he can, but why not try?

So I'm running a small proof of concept.

I came up with my own DIY solution without the NH4 in the original solution and some adjustments like less P and K, as it was a solution ment for fruit baring crops.

I am currently growing RRF directly under my tanks light in a separate jar with the new DIY solution with NO3=25ppm as proxy.

I'm registering the conductivity with my self built conductivity monitor, and double checking with a separate meter.


After the first 7 days they conductivity went from 80 uS/cm to 7 uS/cm, so 2 above the 5 of RO.

My conclusion is they almost taken up all the nutrients in terms of conductivity. No new results as prior test, other than this works with my own solution as well.

 

[PeerUnk]

My next thought was, I might repeat the result by not changing water, but just by dosing the mix. If some build up is taking place, I would notice after a couple of iterations. Right?

So currently I 'm at day 6 of the second iteration, where the conductivity dropped from 90 to 9 uS/cm. So looking decent so far.

Today I decided to investigate some other plants. The floaters Limnobium laevigatum (Amazon Frogbit) and Salvinia minima were selected to have a go with them as well. They might not like super soft water, will see. And I might try some submerged soft water stem plants later on.

So far no issues.

I wander what you think of these experiments...

 

[Pepere]

Well, PPS-Pro as designed uses that technique a bit.

You dose macros and micros daily until tds exceeds a range above what it was after last water change. Then you do another waterchange to reset change to reset.

The goal is dosing what is consumed daily to reduce water changes and fertilizer consumption…

Personally I like the daily dosing. It is just easier for me to do it daily…. And testing over the course of the week shows Nitrates not accumulating or depleting.

Rather than fiddle with TDS reading weekly I just do a weekly water change and then frontload macros to get levels back up where they were before the water change.

 

[BenB]

Personally I like the daily dosing. It is just easier for me to do it daily…. And testing over the course of the week shows Nitrates not accumulating or depleting.

What are your testing results?
I ask because there is always the question with EI of nutrient levels dropping between dosing but not going to 0. However, we never seem to know where that good level is that isn't 0,

 

[PeerUnk]

Well, PPS-Pro as designed uses that technique a bit.

You dose macros and micros daily until tds exceeds a range above what it was after last water change. Then you do another waterchange to reset change to reset.

The goal is dosing what is consumed daily to reduce water changes and fertilizer consumption…

I do see similarities with the PPS-Pro. I’m not trying to copy it, but trying to get a sense of what is actually consumed. And if plants consume everything I have dosed as conductivity went near zero, the consumption of each ion (at least the macros) must be everything I’ve dosed in those ratios.

I’m aware this might work only for specified set of plant species which prefer soft water. How big the set is I don’t know. It looks RRF is one of them.

But it would be so nice to stick a meter in the tank (or in my case look at the data logger) and get an almost instant measurement to see how the water column is doing nutrient wise. Measuring conductivity/TDS is like temperature is fast, specific, trustworthy and accurate. And almost no need for calibration.

Personally I like the daily dosing. It is just easier for me to do it daily…. And testing over the course of the week shows Nitrates not accumulating or depleting.

Rather than fiddle with TDS reading weekly I just do a weekly water change and then frontload macros to get levels back up where they were before the water change.

For some WCs are a no brainer and easy to execute. For me it’s labor intensive and tend to get lazy with it.

Cheers

 

[PeerUnk]

I ask because there is always the question with EI of nutrient levels dropping between dosing but not going to 0. However, we never seem to know where that good level is that isn't 0,

I guess every tank has it’s own rate of uptake, depending on a lot of factors. To my understanding, (full) EI is just ment to be enough for the highest rate, so measuring anything is not needed.

 

[Pepere]

What are your testing results?
I ask because there is always the question with EI of nutrient levels dropping between dosing but not going to 0. However, we never seem to know where that good level is that isn't 0,

Well, I dont know that my dosing is optimum, but I frontload the entire tank 12 ppm nitrate as proxy and over the course of the week the tank cumulatively gets another 12 ppm nitrates.

There have been times I have gotten busy and went an extra week beforegetting the water change..

By and large, the tank hovers in the 10-20 ppm range and closer to the 20 pm.