Do you need to adjust water pH for peat medium?

[Staxx33]

During my first grow I had assumed based on reading that this medium is a little between a soil and hydro and I would pH around 6.0-6.5. However I'm doing some reading and what I'm gathering now is that the pH of the water less important and what is important is the pH of the medium. In true hydroponic systems the medium pH is the water and so yes you would absolutley adjust here. However in non-inert mediums like soil or in my case peat, there is a buffer capacity and the medium will maintain it's pH. Over time the buffer capacity of the medium might degrade and the pH slowly drift, but this is not due to the pH of the water going in, but rather the alkalinity, or hardness (CaCO3).

If this is the case and the medium self regulates. It might not be nessisary at all to add additional chemicals to lower the pH of the water before feeding, and in fact perhaps is better not to? Does anyone else have experience with using something like ProMix HP and just straight tap water?

I am only just starting to read about this and am certianly not a scientist well suited to understand or explain these things. I will link to the two sources that I found that made me question this:

• Very recent blog post from ProMix (MYTH Series: Water pH Relates to Medium pH)
• Discussion on another message board (420Magazine)

As it happens I am just starting my new grow. I have 3 seeds that have just broke soil and have not received any feedings yet. I was already running one as an experiment with dry ammendments instead of liquid nutes to see if I like that style. With the other 2 I am thinking about running an experiment of pH adjusting one while giving the other the same nutes but not using any pH adjustments. I already know my tap water comes out near 8.0 if I add GH Flora Series with lucas formula ratios it sits around 7. Thoughts on this?

 

[Olderfart]

During my first grow I had assumed based on reading that this medium is a little between a soil and hydro and I would pH around 6.0-6.5. However I'm doing some reading and what I'm gathering now is that the pH of the water less important and what is important is the pH of the medium. In true hydroponic systems the medium pH is the water and so yes you would absolutley adjust here. However in non-inert mediums like soil or in my case peat, there is a buffer capacity and the medium will maintain it's pH. Over time the buffer capacity of the medium might degrade and the pH slowly drift, but this is not due to the pH of the water going in, but rather the alkalinity, or hardness (CaCO3).

If this is the case and the medium self regulates. It might not be nessisary at all to add additional chemicals to lower the pH of the water before feeding, and in fact perhaps is better not to? Does anyone else have experience with using something like ProMix HP and just straight tap water?

I am only just starting to read about this and am certianly not a scientist well suited to understand or explain these things. I will link to the two sources that I found that made me question this:

• Very recent blog post from ProMix (MYTH Series: Water pH Relates to Medium pH)
• Discussion on another message board (420Magazine)

As it happens I am just starting my new grow. I have 3 seeds that have just broke soil and have not received any feedings yet. I was already running one as an experiment with dry ammendments instead of liquid nutes to see if I like that style. With the other 2 I am thinking about running an experiment of pH adjusting one while giving the other the same nutes but not using any pH adjustments. I already know my tap water comes out near 8.0 if I add GH Flora Series with lucas formula ratios it sits around 7. Thoughts on this?

I think 7 is going to be too high. I had a look at the promix article, and although it establishes the role of alkalinity in adjusting ph, they still recommend keeping ph below 6.5. As long as you are measuring the ph of your input and runoff, the alkalinity of your water will be dealt with, which makes the article moot.

Bottom line for me is that in anything other than a really effective soil mix, monitoring and controlling ph of both your input and runoff is important. You could also spring for a soil ph meter, but I have not yet gone that far myself.

 

[Kyote]

I use promix hp as a grow medium and I didn't ph my well water on my first grow and had all kinds of problems. After I checked the well water, it is over 7ph. I checked ph after adding nutes (mega crop line) every feeding and watering on my second indoor grow. Made a huge difference. Good luck with your grow!

 

[Egg]

This is fascinating, along with the below. I have been religiously ensuring a nutrient silution pH range of 6.3 - 6.7 and monitoring run off. This week (between week 6 and 7) run off dropped to 5.6 from an input of 6.7!! Nutrients are all Biobizz and no over feeding so I thought that perhaps the balancing agent in the compost (Biobizz All Mix) had worn out and the peat was dragging pH down naturally. I had decided to push pH up to 7.6 - 7.8 next watering (tomorrow) to increase the medium pH and these articles seem to give weight to that approach...

If you are a soil grower the best way to know what is going on with the pH of the soil is with a good pH probe like the Accurate 8.

It is very common for soil pH to vary over time which affects the plants ability to absorb needed nutrients. Plant problems caused incorrect soil pH are probably the most common issue for new growers so monitoring soil pH regularly will help keep your grow on the right track.

If you don't have a good soil pH probe (the cheap ones sold in garden stores are a waste of money) here is the next best method to check your soil pH.

The Pour Thru Method for Testing Container Media

1. water containers to saturation (so that a few drops of water come out of the bottom of the container) with the normal irrigation water they have been receiving

2. after container has drained for one hour, place a saucer under the container

3. pour enough distilled (DI) water on the surface of the container to get 50 mL (1.5 fluid ounces) of leachate to come out of the bottom of the container (Table 1)

4. collect leachate for pH and EC testing

5. calibrate pH and EC meters

6. measure pH and EC of samples

note: don't worry if you don't have an EC meter

>>> If your runoff pH is higher than your starting (water) pH, use this equation to determine your soil pH:*
Soil pH = Runoff pH + Difference

If your runoff pH is lower than your starting pH, us this equation:
Soil pH = Runoff pH - Difference.

For example, say your the starting pH of your solution before it goes in is 6.5 and the pH of your runoff is 7.0. The difference is +0.5, so using the above equation:
Soil pH = 7.0 + 0.5*
Soil pH = 7.5

If your starting pH is 6.5 and your runoff is 6.0, your difference is -0.5 and using the above equation:
Soil pH = 6.0 - 0.5
Soil pH = 5.5