I just mixed up several cubic feet of soil for this year’s grow. Will be using fabric pots for the first time.
Now I want to ‘cover all the bases’ nutrient-wise, so I used a mix of 1/3 Happy Frog, 1/3 Coast of Main, with the rest consisting of peat moss, perlite and my own site-made compost. After saturating, the pH - using two different meters - was just under 8.0. WTF? The the two main ingredients say they are “ready to grow.”
Apparently not…at least right out of the box - or bag.
As a former chemistry major and hospital lab tech, I will retest the supernatant liquid using dip-sticks and the test tube color test. (Gotta wait for the soil sample to settle in the jar of distilled water.) I’ve measured the city water’s used to soak and it’s pH is damn close to neutral.
Do you have a PH pen to test a side by side with the test strips? I generally let my soil slurry mixture rest for several hours and filter it through a regular coffee filter. Hard to get an accurate measurement using the strips 
It’s all good… The original tests used two different soil probes in moist soil. Close to 8, which is not good. With a color-change reagent, it was 5.5 to 6. With a calibrated test ‘pen’ in the clear liquid, pH was 5.83, so I feel much better. What is optimum for TDS?
Cheers
Sounds like you’re going the organic route and I’ve tested some organic amended soils right out of the bag that were considerably high compared to the 900-1200 target using salt based fertilizer but The organic nutrients are more gentle at a higher TDS. I switched over to coco for control reasons.
Amended organic slurry test PPMs
I use Coast of Maine Stonington Blend for all my grows. Only way ill swap is if i start making my own blend. I use their amendments also. Never had an issue. These seedlings were started in Coast of Maine Seedling mix. They are a week out of soil. Second picture is 6 weeks vegged, 3 days 12/12 flip
