Confused about testing soil for ph

Carmarelo

Well-Known Member
I just tested the soil with ph'd 7.0 water, collected the runoff below, and got 6.3 for the widow, and 6.1 for the headband. So what does that make my soil ph? I was reading that you take the readout and minus .2 to get your soil ph. Is this information accurate?
 

Mrgreenfinger

Active Member
its hard to get an exact ph reading from soil unless you have the soil testing kit......but all is good as it is the now.......6.0-6.8 is accepted for soil.......but dont worry to much about it...just make sure what u put in is 6.2-6.4 and ull be fine
 

Grampa

Active Member
I go a few more tenths than .2 but you are on the right track. Here is a post that has really helped me from another canna-board. this method uses a hydro kit but it works the same way.

stinkyattic(different board) said:
There are 3 measurements that are important to know when you are caring for plants growing in a soil or soilless medium.
The first is the pH of your source water.
Next is the pH of your nutrient solution after the fertilizers and [COLOR=#009900 !important]supplements[/COLOR] are added.
Last is the pH of your soil. But that's the hard one! You can't just stick a [COLOR=#009900 !important]pH meter[/COLOR] in the dirt and get an accurate reading, and the cheap metal-probed meters that show this are usually not all that precise.

So how does one determine soil pH accurately? With a runoff test! First, measure the pH of your tap water and record it. As an example, let's say that it is 7.0, exactly neutral.

Now place the pot over a clean rinsed container and pour enough water through the soil to start dripping out the bottom. Collect about 4 ounces of runoff water. Check to see if it is discolored as well.

Now, if you only have liquid indicator, which is just fine, pour this water into a clean small tube or the test vial that came with your pH testing kit.Add a few drops of indicator solution, shake, and read the color change.
If you have a meter, simply stick the electrode in the water and read.

Let's say that your runoff comes out at 6.5. How did that happen? The water passed through a more acidic matrix and dropped its pH. You can assume that your true soil pH is a couple tenths of a pH point lower than the runoff in this case- I'd assume about a 6.2. If it comes out HIGHER, just go in the opposite direction. If it came out 7.5, you can assume that you need to drop down from about 7.8.

You want around 6.0-6.5 for a soilless mix, or 6.3-6.8 for soil.
 

Carmarelo

Well-Known Member
Thanks for the insight guys, I just got my ph pen and am having fun experimenting with it! I tested the nutrient solution I've been feeding my Mr. Nice, and it was way acidic with a reading of 5.1. So I bought some ph up to raise it up to proper levels.
 
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