some measurement

Slippertalk Orchid Forum

Help Support Slippertalk Orchid Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Joined
Dec 16, 2009
Messages
3,805
Reaction score
4,156
In another topik we talked about relations between pH and fertilizer. I bought a pH meter and did some measurements.
Rain water I use is EC= 25-40 uS/cm, pH = 6,85.
Fertilizer solution with Peters Excel CalMag when EC= 500 uS/cm, pH drops to 3,6!!!! It means that every plus 100 uS decrease the pH level cca. with 0,62 !!!
I added 1/3 part tap water to this solution( hardness is 22 nK here), pH increased to 6,2. ( this concentration of fertinizer, what i used before, pure rain water with Peters, 300 uS)
Conclusions:
Peters decreases pH significantly, i used 300uS solution with rain water, pH was cca. 5.0 then, not optimal.
As Brabantia mentioned before, better way to buffer this solution with tapwater.
 
Last edited:
I used to fret over the pH of my fertilizer solutions, making sure it was between 5.5 and 6.5, then I got to talking to a PhD in this field who commented, “Rhizosphere pH is important, but do you know how little the pH of applied solutions affects that?”. The plant and the media - and the microbes within them - apparently play a much bigger role.

What peaked my concern was in some early experiments with plants in semi-hydroponics. The LECA is was using at the time was totally inert or at least neutral in that regard. I was shocked to see that the pH of the solution reservoir plummeted to around 3.5 after a few hours. Then, I saw that it fluctuated with the time of day I tested - I assume that was an indication of the plant going through different processes based upon temperature and light.

Plus there is a question about “how strong” the acid is you’re dealing with. Many fertilizers contain citric acid to aid solubility, and a relatively dilute citric acid solution can exhibit a pH of 2.5, but it’s a really weak acid, so once in the presence of other materials, it cannot keep the pH that low.

If you want to really know what pH your plants are experiencing, do the “pour through” test method:
  • Water the plant thoroughly, drenching the potting medium with the solution of your choice.
  • Wait 60 minutes for the pot to fully drain and for the “pot chemistry” to come to equilibrium.
  • Trickle enough pure water (distilled is best) evenly over the surface of the medium to collect about 50 ml (a shot glass) of the drainage.
  • Test the pH of the collected liquid. That is representative of what the plant experiences.
Since learning all this, I mix my fertilizer consistently and simply don’t worry about it. I also sold my pH meter.

Besides, no fertilizer producer in the world would risk the liability associated with a product that, when used per the label, was damaging to plants.
 
I used to fret over the pH of my fertilizer solutions, making sure it was between 5.5 and 6.5, then I got to talking to a PhD in this field who commented, “Rhizosphere pH is important, but do you know how little the pH of applied solutions affects that?”. The plant and the media - and the microbes within them - apparently play a much bigger role.

What peaked my concern was in some early experiments with plants in semi-hydroponics. The LECA is was using at the time was totally inert or at least neutral in that regard. I was shocked to see that the pH of the solution reservoir plummeted to around 3.5 after a few hours. Then, I saw that it fluctuated with the time of day I tested - I assume that was an indication of the plant going through different processes based upon temperature and light.

Plus there is a question about “how strong” the acid is you’re dealing with. Many fertilizers contain citric acid to aid solubility, and a relatively dilute citric acid solution can exhibit a pH of 2.5, but it’s a really weak acid, so once in the presence of other materials, it cannot keep the pH that low.

If you want to really know what pH your plants are experiencing, do the “pour through” test method:
  • Water the plant thoroughly, drenching the potting medium with the solution of your choice.
  • Wait 60 minutes for the pot to fully drain and for the “pot chemistry” to come to equilibrium.
  • Trickle enough pure water (distilled is best) evenly over the surface of the medium to collect about 50 ml (a shot glass) of the drainage.
  • Test the pH of the collected liquid. That is representative of what the plant experiences.
Since learning all this, I mix my fertilizer consistently and simply don’t worry about it. I also sold my pH meter.

Besides, no fertilizer producer in the world would risk the liability associated with a product that, when used per the label, was damaging to plants.
Ray, many thanks for advices. I use Peters Excel CalMag for about 2 years. Brabantia noted that fertilizer can shift pH srongly to the acidic range, so I measured. Yes, Brabantia has right.Another question if it has any effect on plants. He mentioned too, that this fertilizer does not contain enough Ca and gave an advise to buffer the fertilizing solution with hard tap water. Not an easy question, there are many other factors , media, roots, insects(ants).
 
I used to fret over the pH of my fertilizer solutions, making sure it was between 5.5 and 6.5, then I got to talking to a PhD in this field who commented, “Rhizosphere pH is important, but do you know how little the pH of applied solutions affects that?”. The plant and the media - and the microbes within them - apparently play a much bigger role.

What peaked my concern was in some early experiments with plants in semi-hydroponics. The LECA is was using at the time was totally inert or at least neutral in that regard. I was shocked to see that the pH of the solution reservoir plummeted to around 3.5 after a few hours. Then, I saw that it fluctuated with the time of day I tested - I assume that was an indication of the plant going through different processes based upon temperature and light.

Plus there is a question about “how strong” the acid is you’re dealing with. Many fertilizers contain citric acid to aid solubility, and a relatively dilute citric acid solution can exhibit a pH of 2.5, but it’s a really weak acid, so once in the presence of other materials, it cannot keep the pH that low.

If you want to really know what pH your plants are experiencing, do the “pour through” test method:
  • Water the plant thoroughly, drenching the potting medium with the solution of your choice.
  • Wait 60 minutes for the pot to fully drain and for the “pot chemistry” to come to equilibrium.
  • Trickle enough pure water (distilled is best) evenly over the surface of the medium to collect about 50 ml (a shot glass) of the drainage.
  • Test the pH of the collected liquid. That is representative of what the plant experiences.
Since learning all this, I mix my fertilizer consistently and simply don’t worry about it. I also sold my pH meter.

Besides, no fertilizer producer in the world would risk the liability associated with a product that, when used per the label, was damaging to plants.
Ray, many thanks for advices. I use Peters Excel CalMag for about 2 years. Brabantia noted that fertilizer can shift pH srongly to the acidic range, so I measured. Yes, Brabantia has right.Another question if it has any effect on plants. He mentioned too, that this fertilizer does not contain enough Ca and gave an advise to buffer the fertilizing solution with hard tap water. Not an easy question, there are many other factors , media, roots, insects(ants)
 
This reminds me, I have to measure the pH of my current fertilizer solution. I have done this with my other fertilizers over the years and the result is normally that I first get somewhat of a shock and then that I force myself to forget about it. And nothing changes, exactly as Ray is pointing out.
 

Latest posts

Back
Top