Plant PH/EC/PPM

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

This is the measure of acidity or alkalinity of a solution, on a scale of 1 to 14, where the neutral point is 7. Most plants in soil grow best in a pH6.5 – 7.0conditions, while hydroponically-grown plants prefer slightly more acid conditions. You should aim for a pH of between 5.5 and 6.5. This is the range within which nutrients are most available to plants.

A high pH can reduce the availability of iron, manganese, boron, copper, zinc and phosphorous to plants. A low pH can reduce the availability of potassium, sulphur, calcium, magnesium and phosphorus.

If the pH moves out of the desired range, it can be lowered by the addition of phosphoric or nitric acid to the solution, or raised by adding potassium hydroxide. There are pH adjusters better suited for vegetative growth, and others for fruiting phase.

The pH can be tested by using an indicator solution or a pH meter. This should be done daily. Calibration of the pH meter should be done weekly and the probe kept wet at all times.

Plant pH EC PPM
African Violets 6.0-7.0 1.2-1.5 840-1050
Anthurium 5.0-6.0 1.6-2.0 1120-1400
Antirrhinim 6.5 1.6-2.0 1120-1400
Aphelandra 5.0-6.0 1.8-2.4 1260-1680
Artichoke 6.5-7.5 0.8-1.8 560-1260
Asparagus 6.0-6.8 1.4-1.8 980-1260
Aster 6.0-6.5 1.8-2.4 1260-1680
Banana 5.5-6.5 1.8-2.2 1260-1540
Basil 5.5-6.5 1.0-1.6 700-1120
Bean (Common) 6.0-6.5 1.8-2.4 1400-2800
Beans (Italian bush) 6.0-6.5 1.8-2.4 1400-2800
Beans (Lima) 6.0-6.5 1.8-2.4 1400-2800
Beans (Pole) 6.0-6.5 1.8-2.4 1400-2800
Beetroot 6.0-6.5 0.8-5.0 1260-3500
Begonia 6.5 1.4-2.4 980-1260
Bell peppers 6.0-6.5 1.8-2.8 1400-2000
Black Currant 6.0 1.4-1.8 980-1260
Blueberry 4.0 -5.0 1.8-2.0 1260-1400
Broad Bean 6.0-6.5 1.8-2.2 1260-1540
Broccoli 6.0-6.5 2.8-3.5 1960-2450
Bromeliads 5.0-7.5 0.8-1.2 560-840
Brussell Sprout 6.5-7.5 2.5-3.0 1750-2100
Cabbage 6.5-7.0 2.5-3.0 1750-2100
Caladium 6.0-7.5 1.6-2.0 1120-1400
Canna 6.0 1.8-2.4 1260-1680
Capsicum 6.0-6.5 1.8-2.2 1260-1540
Carnation 6.0 2.0-3.5 1260-2450
Carrots 6.3 1.6-2.0 1120-1400
Cauliflower 6.0-7.0 0.5-2.0 1050-1400
Celery 6.5 1.8- 2.4 1260-1680
Chicory 5.5-60 2.0-2.4 1400-1600
Chives 6.0-6.5 1.8-2.4 1260-1540
Chrysanthemum 6.0-6.2 1.8-2.5 1400-1750
Cucumber 5.8-6.0 1.7-2.5 1190-1750
Cymbidiums 5.5 0.6-1.0 420-560
Dahlia 6.0-7.0 1.5-2.0 1050-1400
Dieffenbachia 5.0 1.8-2.0 1400-1680
Dracaena 5.0-6.0 1.8-2.4 1400-1680
Eggplant 5.5-6.5 2.5-3.5 1750-2450
Endive 5.5 2.0-2.4 1400-1680
Fennel 6.4-6.8 1.0-1.4 700-980
Ferns 6.0 1.6-2.0 1120-1400
Ficus 5.5-6.0 1.6-2.4 1120-1680
Fodder 6.0 1.8-2.0 1260-1400
Freesia 6.5 1.0-2.0 700-1400
Garlic 6.0 1.4-1.8 980-1260
Gerbera 5.0-6.5 2.0-2.5 1400-1750
Gladiolus 5.5-6.5 2.0-2.4 1400-1680
Hot Peppers 6.0-6.5 1.8-2.8 1400-2000
Impatiens 5.5-6.5 1.8-2.0 1260-1400
Lavender 6.4-6.8 1.0-1.4 700-980
Leek 6.5-7.0 1.4-1.8 980-1260
Lemon Balm 5.5-6.5 1.0-1.6 700-1120
Lettuce 5.5-6.5 0.8-1.2 560-840
Marjoram 6.0 1.6-2.0 1120-1400
Marrow 6.0 1.8-2.4 1260-1680
Melon 5.5-6.0 2.0-2.5 1400-1750
Mint 5.5-6.0 2.0-2.4 1400-1680
Monstera 5.0-6.0 1.8-2.4 1400-1680
Mustard Cress 6.0-6.5 1.2-2.4 840-1680
Okra 6.5 2.0-2.4 1400-1680
Onions 6.0-6.7 1.4-1.8 980-1260
Pak-choi 7.0 1.5-2.0 1050-1400
Palms 6.0-7.5 1.6-2.0 1120-1400
Parsley 5.5-6.0 0.8-1.8 560-1260
Parsnip 6.0 1.4-1.8 980-1260
Granadilla 6.5 1.6-2.4 840-1680
Paw-Paw 6.5 2.0-2.4 1400-1680
Pea 6.0-7.0 0.8-1.8 980-1260
Peas (Sugar) 6.0-6.8 0.8-1.8 980-1260
Pepino 6.0-6.5 2.0-5.0 1400-3500
Peppers 5.8-6.3 1.8-2.8 1400-2000
Pineapple 5.5-6.0 2.0-2.4 1400-1680
Potato 5.0-6.0 2.0-2.5 1400-1750
Pumpkin 5.5-7.5 1.8-2.4 1260-1680
Radish 6.0-7.0 1.6-2.2  840-1540
Red Currant 6.0 1.4-1.8 980-1260
Rhubarb 5.0- 6.0 1.6-2.0 840-1400
Rosemary 5.5-6.0 1.0-1.6 700-1120
Roses 5.5-6.0 1.5-2.5 1050-1750
Sage 5.5-6.5 1.0-1.6 700-1120
Silverbeet 6.0-7.0 1.8-2.3 1260-1610
Spinach 5.5-6.6 1.8-2.3 1260-1610
Squash 5.0-6.5 1.8-2.4 1260-1680
Strawberries 5.5-6.5 1.8-2.2 1260-1540
Sweet Corn 6.0 1.6-2.4 840-1680
Sweet Potato 5.5-6.0 2.0-2.5 1400-1750
Swiss Chard 6.0 6.5 1.8-2.3 1260-1610
Taro 5.0-5.5 2.5-3.0 1750-2100
Thyme 5.5-7.0 0.8-1.6 560-1120
Tomato 5.5-6.5 2.0-5.0 1400-3500
Turnip 6.0-6.5 1.8-2.4 1260-1680
Watercress 6.5-6.8 0.4-1.8 280-1260
Watermelon 5.8 1.5-2.4 1260-1680
Zucchini 6.0 1.8-2.4 1260-1680