EC – Electrical Conductivity

This is a measurement of the strength of a nutrient solution. It is also known as CF (Conductivity Factor), but since CF is only one decimal place away from EC, we will stick to EC. The measurement of EC is in milliSiemens per cm (mS/cm). It is a measurement of the strength of the nutrient solution as a whole and will not tell you if one or more of the nutrient salts is out of balance. Plants take up different nutrient salts at different stages of growth and in different climatic conditions, as well as different pH levels.. The speed that different nutrient salts are taken up also varies. For instance, nitrogen is taken up quite quickly, but calcium is a slow mover! For the home grower it is advisable to change the nutrient solutions at regular intervals, say every week in summer and every two weeks in winter.

If the EC rises, it means that the plants are taking up water faster than nutrients. This usually happens in hot weather, when the plant tries to keep cool. When this happens you add water until the required EC is reached. On the other hand, if the EC falls, the plant is taking up more nutrients than water, so you have to add more nutrients.

If you are a serious home grower you will obtain an EC meter and have the peace of mind that your plants are being fed optimally. The EC meter should be calibrated regularly, say once a month.

The practical use of EC readings becomes apparent when you realize that plants can be categorized into low, medium and heavy feeders. It follows from this that you should feed plants in the same category together from one reservoir if you are going to attain optimum results. If you feed lettuce with a high EC intended for tomatoes, the lettuce can become bitter. Likewise, if you feed tomatoes with a low EC, suitable for lettuce, the tomatoes will be tasteless!

pH