How to measure pH & EC from the roots?
Sometimes, although you have measured the pH and EC of your feed solution and these are as they should be, these may have changed by the time the feed solution reaches the roots, causing problems for your plants. One way to tell that this is happening is from the smell of the soil around the roots, but the best way is to use a pH meter and an EC meter. The right pH and EC will help you to get the very best results as a grower.
You can test the substrate sample when it has the maximum level of moisture. Slowly add demineralized water until the substrate sample stops absorbing any more. The most reliable method is to dilute the substrate by adding still more fluid. Add the wet substrate to some more demineralized water (which has an EC of 0.0) and stir them together well.
Make sure that your meters have been properly calibrated before checking the sample, otherwise you will not get an accurate measurement. If necessary, you will need to correct the EC and/or pH when you next prepare feed solution for your plants. Remember that the EC is supposed to rise in the first weeks. Keep your growing schedule handy, because if you get different measurements in different weeks this does not necessarily mean that there is a problem.