Plant pH/EC/TDS/PPM

EC – Electrical Conductivity ( TDS – Total Dissolved Solids)

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!

Convert TDS and EC readings
TDS = EC reading (in milliSiemens/cm) times 1000 and divide by 2.
EC = PPM times 2 divide by 1000

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.

PlantpHECPPM
African Violets6.0-7.01.2-1.5840-1050
Anthurium5.0-6.01.6-2.01120-1400
Antirrhinim6.51.6-2.01120-1400
Aphelandra5.0-6.01.8-2.41260-1680
Artichoke6.5-7.50.8-1.8560-1260
Asparagus6.0-6.81.4-1.8980-1260
Aster6.0-6.51.8-2.41260-1680
Banana5.5-6.51.8-2.21260-1540
Basil5.5-6.51.0-1.6700-1120
Bean (Common)6.0-6.51.8-2.41400-2800
Beans (Italian bush)6.0-6.51.8-2.41400-2800
Beans (Lima)6.0-6.51.8-2.41400-2800
Beans (Pole)6.0-6.51.8-2.41400-2800
Beetroot6.0-6.50.8-5.01260-3500
Begonia6.51.4-2.4980-1260
Bell peppers6.0-6.51.8-2.81400-2000
Black Currant6.01.4-1.8980-1260
Blueberry4.0 -5.01.8-2.01260-1400
Broad Bean6.0-6.51.8-2.21260-1540
Broccoli6.0-6.52.8-3.51960-2450
Bromeliads5.0-7.50.8-1.2560-840
Brussell Sprout6.5-7.52.5-3.01750-2100
Cabbage6.5-7.02.5-3.01750-2100
Caladium6.0-7.51.6-2.01120-1400
Canna6.01.8-2.41260-1680
Cannabis Indica6.0-6.5 Soil – 5.8 Hydro/Coco2.4-2.81680-1960
Cannabis Sativa6.0-6.5 Soil – 5.8 Hydro/Coco1.0-1.5700-1050
Capsicum6.0-6.51.8-2.21260-1540
Carnation6.02.0-3.51260-2450
Carrots6.31.6-2.01120-1400
Cauliflower6.0-7.00.5-2.01050-1400
Celery6.51.8- 2.41260-1680
Chicory5.5-602.0-2.41400-1600
Chives6.0-6.51.8-2.41260-1540
Chrysanthemum6.0-6.21.8-2.51400-1750
Cucumber5.8-6.01.7-2.51190-1750
Cymbidiums5.50.6-1.0420-560
Dahlia6.0-7.01.5-2.01050-1400
Dieffenbachia5.01.8-2.01400-1680
Dracaena5.0-6.01.8-2.41400-1680
Eggplant5.5-6.52.5-3.51750-2450
Endive5.52.0-2.41400-1680
Fennel6.4-6.81.0-1.4700-980
Ferns6.01.6-2.01120-1400
Ficus5.5-6.01.6-2.41120-1680
Fodder6.01.8-2.01260-1400
Freesia6.51.0-2.0700-1400
Garlic6.01.4-1.8980-1260
Gerbera5.0-6.52.0-2.51400-1750
Gladiolus5.5-6.52.0-2.41400-1680
Hot Peppers6.0-6.51.8-2.81400-2000
Impatiens5.5-6.51.8-2.01260-1400
Lavender6.4-6.81.0-1.4700-980
Leek6.5-7.01.4-1.8980-1260
Lemon Balm5.5-6.51.0-1.6700-1120
Lettuce5.5-6.50.8-1.2560-840
Marjoram6.01.6-2.01120-1400
Marrow6.01.8-2.41260-1680
Melon5.5-6.02.0-2.51400-1750
Mint5.5-6.02.0-2.41400-1680
Monstera5.0-6.01.8-2.41400-1680
Mustard Cress6.0-6.51.2-2.4840-1680
Okra6.52.0-2.41400-1680
Onions6.0-6.71.4-1.8980-1260
Pak-choi7.01.5-2.01050-1400
Palms6.0-7.51.6-2.01120-1400
Parsley5.5-6.00.8-1.8560-1260
Parsnip6.01.4-1.8980-1260
Granadilla6.51.6-2.4840-1680
Paw-Paw6.52.0-2.41400-1680
Pea6.0-7.00.8-1.8980-1260
Peas (Sugar)6.0-6.80.8-1.8980-1260
Pepino6.0-6.52.0-5.01400-3500
Peppers5.8-6.31.8-2.81400-2000
Pineapple5.5-6.02.0-2.41400-1680
Potato5.0-6.02.0-2.51400-1750
Pumpkin5.5-7.51.8-2.41260-1680
Radish6.0-7.01.6-2.2 840-1540
Red Currant6.01.4-1.8980-1260
Rhubarb5.0- 6.01.6-2.0840-1400
Rosemary5.5-6.01.0-1.6700-1120
Roses5.5-6.01.5-2.51050-1750
Sage5.5-6.51.0-1.6700-1120
Silverbeet6.0-7.01.8-2.31260-1610
Spinach5.5-6.61.8-2.31260-1610
Squash5.0-6.51.8-2.41260-1680
Strawberries5.5-6.51.8-2.21260-1540
Sweet Corn6.01.6-2.4840-1680
Sweet Potato5.5-6.02.0-2.51400-1750
Swiss Chard6.0 6.51.8-2.31260-1610
Taro5.0-5.52.5-3.01750-2100
Thyme5.5-7.00.8-1.6560-1120
Tomato5.5-6.52.0-5.01400-3500
Turnip6.0-6.51.8-2.41260-1680
Watercress6.5-6.80.4-1.8280-1260
Watermelon5.81.5-2.41260-1680
Zucchini6.01.8-2.41260-1680