Phosphate Minimums - The Planted Tank Forum
 2Likes
  • 2 Post By Jeff5614
  • 2 Post By Edward
 
LinkBack Thread Tools Display Modes
post #1 of 5 (permalink) Old 11-11-2017, 11:21 PM Thread Starter
Wannabe Guru
 
PTrader: (0/0%)
Join Date: Feb 2017
Location: PA
Posts: 1,525
Phosphate Minimums

I've been wondering about trying to balance low levels (2-4 ppm) of PO4 and just encountered this very old thread by Tom Barr:

Quote:
The other issue, bioavaoilabilility.
Make sure the readings are inorganic biobvailabale plant nutrients, when you get down to the lower ranges, the fraction of organic N and P increases relative to what is really available to the plants.

This is why some assume they have enough at 2ppm of NO3, but stunt their plants.

Same with PO4.
He then went on with:

Quote:
If you limit PO4, then that downregulates the uptake of NO3/NH4/CO2 and light use efficiency. Ole and Troels did any experiement at tRopica detailing some of the CO2-light dynamics.
No one else in the thread picked-up on it, but it seems to imply that low PO4 levels may be significantly reducing uptake of other nutrients. However, I can't see where that level might be. It's as though he's saying that the accumulation of PO4 might be 'stale' and that it needs to be constantly added freshly (maybe also reinforcing the need for WC's from a resetting standpoint).

Can anyone comment on this bioavailability aspect of PO4?
Deanna is offline  
Sponsored Links
Advertisement
 
post #2 of 5 (permalink) Old 11-11-2017, 11:33 PM
Planted Tank Guru
 
Jeff5614's Avatar
 
PTrader: (52/100%)
Join Date: Dec 2005
Location: TN
Posts: 3,603
Quote:
Originally Posted by Deanna View Post
I've been wondering about trying to balance low levels (2-4 ppm) of PO4 and just encountered this very old thread by Tom Barr:



He then went on with:



No one else in the thread picked-up on it, but it seems to imply that low PO4 levels may be significantly reducing uptake of other nutrients. However, I can't see where that level might be. It's as though he's saying that the accumulation of PO4 might be 'stale' and that it needs to be constantly added freshly (maybe also reinforcing the need for WC's from a resetting standpoint).

Can anyone comment on this bioavailability aspect of PO4?
Nothing other than low PO4 levels will inhibit uptake of other nutrients as you've mentioned including uptake of carbon. One way to decrease CO2 demand is by lowering your PO4 levels. Of course if you go too low then you run into issues.

Not sure if this article will be helpful to you, but there is mention of PO4 limitation and nonplant available phosphates.

https://barrreport.com/barr-report-r...05crevised.pdf
Deanna and Deanna like this.
Jeff5614 is offline  
post #3 of 5 (permalink) Old 11-11-2017, 11:39 PM
Planted Tank Guru
 
xmas_one's Avatar
 
PTrader: (18/100%)
Join Date: Feb 2010
Location: Oregon
Posts: 3,402
https://en.m.wikipedia.org/wiki/Lieb...of_the_minimum


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
xmas_one is offline  
 
post #4 of 5 (permalink) Old 11-12-2017, 01:12 AM Thread Starter
Wannabe Guru
 
PTrader: (0/0%)
Join Date: Feb 2017
Location: PA
Posts: 1,525
@Jeff5614 Yes; a very informative article. It states:
Quote:
plant uptake forces the PO4-3 levels down to zero or only non plant available dissolved organic phosphate (DOP) forms
Which, in my mind, begs the question: do our PO4 tests measure only PO4-3 or will they also pick-up the DOP and, therefore, mislead us into thinking there is plant usable phosphate, when there is not?

@xmas_one Thanks, but this is not about Liebig's law of the minimum - DIRECTLY. However, if DOP is misleading us into thinking PO4-3 is plentiful, when it is not, then that law is violated.

Do any other readers know if our hobbyist grade PO4 tests measure only orthophosphate and not DOP? I could find only one data point that claims PO4 test kits measure only inorganic phosphates. If true, I wonder what organic phosphates do to our tanks. Perhaps it's a good reason to use chemical filters, if there are any that will filter DOP and not orthophosphate.

Another thought here is that we have affirmed that adding orthophosphate does not induce algae. However, I think that organic phosphates do. So, it may be a little bit wrong to say that phoshates don't induce algae. Might be better to say that adding orthophosphate doesn't induce algae.

Last edited by Deanna; 11-12-2017 at 02:14 AM. Reason: add
Deanna is offline  
post #5 of 5 (permalink) Old 12-01-2017, 10:57 PM
Wannabe Guru
 
Edward's Avatar
 
PTrader: (0/0%)
Join Date: Apr 2005
Location: at home
Posts: 1,343
Hi Deanna,
You can find out whether the test kit reads inorganic PO4 only.
By discontinuing PO4 dosage and watching PO4 dropping to zero. It should take few days to a week depending on the starting level and plant uptake. Generally, plants suck up more P than they need and store it. Also, there is no risk leading to P deficiency for few days as P is a mobile element.

My Hagen Nutrafin PO4 test reads zero when PO4 dosing is low.

Thank you
Edward


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Edward is online now  
Reply

Tags
None

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the The Planted Tank Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome