The pH and electro-conductivity values specified here are given as a broad range. It should be noted that specific plant requirements will vary according to regional climatic conditions, and from season to season within that region. These values are intended for Hydroponic plants only (soil grown plants will differ). Electro-Conductivity (EC) or Conductivity Factor (cF) can be expressed as either milliSiemens (mS), cF, or parts per million (PPM) 1 mS = 10cF = 700ppm.
As a general rule, plants will have a higher nutrient requirement during cooler months, and a lower requirement In the hottest months. Therefore, a stronger nutrient solution should be maintained during winter, With a weaker solution during summer when plants take up and transpire more water than nutrients.