PPM level vs usage vs repleneshing

[Have2]

I am wondering if anyone can chime in..

Let's say a RDWC user is running his system at 800 ppm. Each day, it refills with nutrients on a steady injection of 150ppm equivalent each day. System's ppm is stable so the plants are consuming everything that is added.

If the same user runs the same system at 500 and still add for 150ppm equivalent each day.

What is the best? 500 ppm? 800? Would the plants eat more if they were in a 800 ppm solution or they will eat the same? Advantages? Cons?

Thanks!

 

[Larry3215]

Are you talking about an automated system? Im also not sure what you mean by "an equivalent 150 PPM"? What exactly are you adding?

In any case, there is no fixed or perfect PPM level. Every plant is different, and different types of hydro have different feed levels. For example, some types of aero allow you to run as low as 1/4 of "normal" PPM's.

Its best to let the plant(s) tell you what it wants. Just watch the leaves. If they are pale, they need more. If they are too dark, or tips burning, they need less. Its not unusual when you have several plants sharing the same rez for some to look a little light and some to look a little dark. Many people like to push it till the tips are barely burning. I prefer to back off from there, but every one is different.

Im not sure how valid this chart is, but its been floating around for years. As far as Im concerned, recirculating rez diagnosis is a black art at best. I think each instance will be unique to the situation, and I doubt anyone fully understands it Thats why I am so happy I switched to Drain to waste.

 

[Have2]

Are you talking about an automated system? Im also not sure what you mean by "an equivalent 150 PPM"? What exactly are you adding?

In any case, there is no fixed or perfect PPM level. Every plant is different, and different types of hydro have different feed levels. For example, some types of aero allow you to run as low as 1/4 of "normal" PPM's.

Its best to let the plant(s) tell you what it wants. Just watch the leaves. If they are pale, they need more. If they are too dark, or tips burning, they need less. Its not unusual when you have several plants sharing the same rez for some to look a little light and some to look a little dark. Many people like to push it till the tips are barely burning. I prefer to back off from there, but every one is different.

Im not sure how valid this chart is, but its been floating around for years. As far as Im concerned, recirculating rez diagnosis is a black art at best. I think each instance will be unique to the situation, and I doubt anyone fully understands it Thats why I am so happy I switched to Drain to waste.

View attachment 4765277

150 ppm equivalent... I mean, each day, coco, grow A and grow B are injected to cover the ppm's drop.

Example: So let's say you flush the system and start with 500 ppm. Next day, it falls to 350 ppm if you add nothing.
So you can think at it as a way that the plants consume 150 ppm. So you can calculate how much coco/ and other stuff to add for you to maintain the 500ppm.

I was wondering, knowing that the system "eats" 150 ppm. If it changes something to be at 500 ppm vs 800 and keep adding the 150 ppm it consumes...

Is it clearer? Maybe I smoked a tad too much lol

 

[Have2]

Are you talking about an automated system? Im also not sure what you mean by "an equivalent 150 PPM"? What exactly are you adding?

In any case, there is no fixed or perfect PPM level. Every plant is different, and different types of hydro have different feed levels. For example, some types of aero allow you to run as low as 1/4 of "normal" PPM's.

Its best to let the plant(s) tell you what it wants. Just watch the leaves. If they are pale, they need more. If they are too dark, or tips burning, they need less. Its not unusual when you have several plants sharing the same rez for some to look a little light and some to look a little dark. Many people like to push it till the tips are barely burning. I prefer to back off from there, but every one is different.

Im not sure how valid this chart is, but its been floating around for years. As far as Im concerned, recirculating rez diagnosis is a black art at best. I think each instance will be unique to the situation, and I doubt anyone fully understands it Thats why I am so happy I switched to Drain to waste.

View attachment 4765277

If you added the arrow...
Azote uptake raises the ph... And potassium uptake lowers the ph... (Ion exchange) That's why in veg, ph is going up and in bloom, going down

 

[Larry3215]

Example: So let's say you flush the system and start with 500 ppm. Next day, it falls to 350 ppm if you add nothing.
So you can think at it as a way that the plants consume 150 ppm. So you can calculate how much coco/ and other stuff to add for you to maintain the 500ppm.

I was wondering, knowing that the system "eats" 150 ppm. If it changes something to be at 500 ppm vs 800 and keep adding the 150 ppm it consumes...

Is it clearer? Maybe I smoked a tad too much lol

Ok, I think I get it. I dont think it matters where you start from. If the EC is dropping, something is off. Is the plant drinking - water level falling? What is the PH doing?

If you added the arrow...
Azote uptake raises the ph... And potassium uptake lowers the ph... (Ion exchange) That's why in veg, ph is going up and in bloom, going down

LOL I havent heard the term Azote since highschool chem class - and I think it was archaic even then Its my understanding that the PH can go either way depending on the nitrogen source in the nutes - amonia based or nitrate based. One drives it up and one drives it down. I have no clue on coco nutes, so I will have to leave that to you. There are a number of different things that can drive PH swings. As far as I know, the nitrogen cycle isnt dominate or even a major source of PH changes, but I havent looked at that. To be honest, chemistry isnt my strong suit. Im relying on decades old memories here from college classes.

I was also under the impression that that cycle takes a fair amount of time - much slower than on a daily basis - but again, coco is not my thing.

I never saw any change in PH swings when I went from veg to flower, but I also never changed my nutes between veg and flower. I have always fed the same thing start to finish.

Maybe Im not the best one to dive into the chemistry with you, but when I was recirculating nutes - Im drain to waste now - changes in EC between rez changes were always a bad sign - of something. Often more than one thing. Recirculating sucks in my opinion

 

[Have2]

Ok, I think I get it. I dont think it matters where you start from. If the EC is dropping, something is off. Is the plant drinking - water level falling? What is the PH doing?

LOL I havent heard the term Azote since highschool chem class - and I think it was archaic even then Its my understanding that the PH can go either way depending on the nitrogen source in the nutes - amonia based or nitrate based. One drives it up and one drives it down. I have no clue on coco nutes, so I will have to leave that to you. There are a number of different things that can drive PH swings. As far as I know, the nitrogen cycle isnt dominate or even a major source of PH changes, but I havent looked at that. To be honest, chemistry isnt my strong suit. Im relying on decades old memories here from college classes.

I was also under the impression that that cycle takes a fair amount of time - much slower than on a daily basis - but again, coco is not my thing.

I never saw any change in PH swings when I went from veg to flower, but I also never changed my nutes between veg and flower. I have always fed the same thing start to finish.

Maybe Im not the best one to dive into the chemistry with you, but when I was recirculating nutes - Im drain to waste now - changes in EC between rez changes were always a bad sign - of something. Often more than one thing. Recirculating sucks in my opinion

I'm not in coco, I was talking about coco as coco-cal (should have used cal-mag supp, my bad!, Current culture uses the term coco-cal) As for my water level, the float valve is connected to a R/O system, so always at the wanted level with fresh R/O water.

As for my ph, it's stable, with an slow increase over time when in grow mode... As for the Azote, yeah... ahaha I should have used Nitrogen

As for my explanation, here's a nice text that sums up :

"The ratio in uptake of anions and cations by plants may cause substantial shifts in pH. In general, an excess of cation over anion leads to a decrease in pH, whereas an excess of anion over cation uptake leads to an increase in pH. That is, when the anions are uptaken in higher concentrations than cations the plant excretes OH- or HCO3- anions to balance the electrical charges inside, which increases the pH value. For example, if a plant absorbs the negatively charged nitrate nitrogen (NO3-) heavily it will start to contribute more OH – than H3O + ions into the solution and the result will be an increase in pH. On the other hand, if the plant absorbs high levels of the positively charged potassium (K+) it will contribute more H3O + than OH – ions and the result will be a decrease in pH. "

So, yeah, even if you switch from veg to bloom nuts, it won't change the ph switch, it's the phase of the crop that will. I saw it nicely on my last grow.
By the way, recirculating ROCKS, in my opinion

My main question/interrogation was... even if we "readd" the uptaken ppm to keep the ppm stable, will the plant reacts differently in a 500 ppm or a 800 ppm solution. I tend to believe it won't because, if it drops 150 ppm in a day and you replenish them, plant was getting all she wanted... I also do that, raise ppm slowly until I see some tips burning then back a little BUT, if it's not worth it because I can see how much they "eat" all they need, no point on chasing that.

 

[Larry3215]

I can see your logic, but I think this is one of those things that sits the black arts category You will just have to see what works for your specific situation.

There are just too many variables when recirculating. Your water - how hard or soft it is, your nutes - organic vrs pure salts, the nitrogen source balance, water temps, the biological load in the system - algae, good/bad bacteria, vrs added beneficial bacteria vrs sterile. Thats not even to mention the roots themselves and their influence on the chemistry of the system via exhudates, root health, and nute uptake variables.

I love drain to waste because I dont have to think about any of that stuff. I fill my rez, and nothing changes for the next 5 to 10 days while it drains out. I do have to monitor PH occasionally. I have well water with a hi mineral content which means I have a slow drift back up after lowering it to 5.5-5.6. But that takes several days. I actually like the slow increase. If I keep the rez cold enough, its the perfect range from 5.5 to 6.1 over the time it takes to drain out.

To each his own as they say. If it runs your motor - go for it