The ideal pH range for a nutrient solution is typically between 5.8 and 6.5. A pH value above or below this range can increase the likelihood that some nutrients become unavailable to the plant. A pH value of 6.3 typically works well for most plants.
Some electronic meters require a ‘two point’ calibration. pH BUFFER 4 is important as the lower calibration point in the two point calibration process. This will ensure that meters accurately reflect the true reading at the lower end of the range.