Differing Ph levels.

[Cerul]

Hi guys,

I had a question about Ph levels when growing in soil.
Which Ph level is more important- The Ph of the soil or the Ph of the runoff water?
I have my seedling in a mix of Mass Whole's seedling mix and Master's mix 50/50. My nute mix is going in at a Ph of 6.4 and the Ph of my runoff says its 5.6. When I stick my soil Ph meter into the soil the reading on it comes up as Ph of 2.0. I'm very confused. Is this a problem or is this ok?

 

[Renaissance Redneck]

I think your soil meter is lying to you, Brother. It may be getting a false reading.
Is your soil moist when you test? I'll guess it is. What brand meter are you using?

 

[Cerul]

It's a cheap $7.45 Ph & moisture tester. It just says "Two-way tester" on it.

 

[Renaissance Redneck]

Gottcha.
You can't test soil pH with a liquid meter. Accurate 8 meters have been showing very well for testing soil, it might be worth investing in.
For your pH in and out, just make sure you have calibration fluid to make sure you're on the mark.
In vs out will only give you a rough guestimate of what your soil is doing, but it will get you in the ballpark.
PH Calculation Guide by GoAuto6

Rough Calculation Guide:

Here's some good info on ph.....
If your runoff pH is higher than your starting 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

Based on your numbers, you're around 4.8, way, way low.
That's lock-out city. Do you have calibration fluid? If not, how about lemon juice or distilled water?
How old are your plants?

 

[Cerul]

My plant is a 9 day old seedling. It was growing ok for the first 5 days and for the last 4 days it hasn't shown any significant growth. The cheap Ph tester is one for soil and has 2 very long prongs that go into soil. I have separate Milwaukee Ph tester for liquids.

Thanks for those formulas! I'm going to have to water with about a Ph of 7.5 per those eqautions.

 

[Renaissance Redneck]

Trust your pen, scrap the cheepy soil tester. Just make sure your pen is calibrated. You should have at least two calibration fluids, and a storage fluid.
I'd adjust gradually.... pH your water to 7.0 to start and work up from there. At 9 days, you're probably watering pretty often.
When the budget allows, get an Accurate 8 for direct soil testing

 

[Scrappy]

I just bought an a8 it's great also falls right in line with the ph test. you test runoff to check ph if u ain't got a pen. the a8 is pricy but nice to have around as u can test bag right out of the soil and make corrections as needed.

 

[Cerul]

Hi Renaissance Redneck,

After a bunch of calculations and using only my Milwaukee pen I've come to the conclusion that my soil Ph is between 2.2 and 2.6.
My seedling has stopped growing or is growing excruciatingly slow. The pic below is my seedling at 2 weeks. How do I get the soil to the right Ph? Also, can my auto be salvaged? Really frustrated- I thought good quality soils came with an adjusted Ph level....

 

[Renaissance Redneck]

Morning, Cerul!
Just to double check, what is your water in and run off pH? Have you calibrated your pen?
a reading in the 2 range for pH is insanely acidic for soil.

 

[Cerul]

Morning RR,

I did calibrate my pen and store it in a calibrated solution of Ph 7. I make sure between each test to wash the probe tip and dip it in the calibrated solution to make sure it is consistent.
So I did a couple of tests each time when I felt the soil had dried out. The first time I watered with a Ph of 8.0 and the runoff came to 5.2. So the soil Ph would come 2.8. I waited for the soil to dry out again and this time watered with a Ph of 10.0 and the runoff came to 6.1. This time the soil Ph came to 2.2.
I hope I'm running the calculations right.