Electric conductivity

Electrical conductivity , also known as conductivity or EC value (from English electrical conductivity ), is a physical quantity that indicates how strong the ability of a substance is to conduct electric current. This value, among many others, is used to control the fertilizer concentration in aquaponics and hydroponics. 

 

The higher the temperature, the lower the oxygen content in the nutrient solution:

Temperature (°C)	Dissolved oxygen in water (mg/l)
10	11.30
15	10.00
20	9.00
25	8.30
30	7.60
35	7:00
40	6.40
45	6:00 am

 

 

pH value hydroponics - approx. pH 6.2

The acidity (pH value) of the water influences the availability of nutrients for the plants. A wide range of nutrients can best be absorbed by the roots in a  pH range of 5.5 - 6.5  , regardless of the cultivation method.

The pH should be measured and adjusted to create favorable growth conditions. Since the plants do not like a pH change that is too rapid, the pH value adjustment should be done gradually.

The following rounded minimums and maximums from the 4 nutrient formulas are good guidelines for your own hydroponic nutrient solution:

element	mg/l = ppm
Nitrogen (N)	170 – 235
Phosphorus (P)	30 – 60
Potassium (K)	150 – 300
Calcium (Ca)	160 – 185
Magnesium (Mg)	35 – 50
Sulfur (S)	50-335
Iron (Fe)	2.5 – 12
Manganese (Mn)	0.5 – 2.0
Copper (Cu)	0.02 – 0.1
Zinc (Zn)	0.05 – 0.1
Molybdenum (Mo)	0.01 – 0.2
boron (B)	0.3 – 0.5

 

 

When growing hydroponically, it is advisable to allow the pH to fluctuate slightly within 6-7 pH. As you can see in the figure, some nutrients can only be absorbed at the lower or upper range of the optimal range. 

 

 

Herbs for growing in hydroponics

Herbs thrive in hydroponics, grow very well and you can grow many herbs in a small space. If, as with classic cultivation in soil, you take into account the requirements for sun, partial shade or shade and keep an eye on the water-nutrient mixture, you can look forward to a rich harvest.

Regular pruning also promotes plant growth. The list shows herbs that are well suited for hydroponic cultivation, but does not claim to be complete.    

• valerian
• basil
• Savory
• Borage
• Watercress
• Calendula
• dill
• Echinacea
• Angelica
• tarragon

• fennel
• Goldenseal
• chamomile
• Catnip
• chervil
• coriander 
• cumin
• lavender
• Lovage
• dandelion

• marjoram
• Mint, all varieties
• Feverfew
• oregano
• Parsley
• Pimpinelle
• peppermint
• Rue / rocket
• rosemary
• sage

• chives
• Cut celery
• Stevia
• thyme
• Thai basil
• Wormwood
• Hyssop (verbena)
• Lemon basil
• Lemongrass
• Lemon balm

Vegetables for growing in hydroponics

Actually, you can grow almost all plants hydroponically, except root vegetables. Fast-growing varieties such as pak choi, Asian lettuce or chard are interesting because they can be harvested frequently. But many other types of vegetables also deliver high yields quickly and taste very good at the same time. The list shows examples of which vegetables can be cultivated hydroponically. 

• eggplant
• Asian salad
• cauliflower
• Beans
• Broccoli
• chili
• endive salad
• Peas

• Strawberries
• Green mustard
• Kale
• Cucumbers
• Kohlrabi
• herb
• pumpkin
• Leek

• Chard
• Melons
• Mizuna - Japanese salad
• okra
• Pak choi
• paprika
• Brussels sprouts
• Red mustard

pH value and EC value for crops

pH values ​​and EC values ​​for ornamental plants

 EC values ​​for hemp plants

Composition of a hydroponic nutrient solution (standard nutrient solution)

In hydroponic science, extensive research has been and is being carried out to find the best nutrient solution. Four standard nutrient formulas from Hoagland & Arnon (1938), Hewitt (1966), Cooper (1979) and Steiner (1984) are particularly well known. These are general standard nutrient solutions.

Here you will find a short introduction to how you can create nutrient solutions yourself.

The following rounded minimums and maximums from the 4 nutrient formulas are good guidelines for your own hydroponic nutrient solution:

pH of the nutrient solution and nutrient availability

In order for your plant to grow and thrive in hydroponics, your nutrient solution must have a certain pH value. If the pH value is too high or too low, important nutrients are not available to the plant.

In most cases, the ideal pH value of the nutrient solution is between 5.5 – 6.5 . Most nutrients are available in this area. If you want to perfect yield and growth, you should find out about specific pH values ​​for plants in hydroponics. Here is a diagram about the pH value and the availability of nutrients:

 Graphic: Pennsylvania State University

First of all: the values ​​described in the following table should be treated with caution. Of course, even within the same order, down to the genus, the differences are enormous. What a healthy tomato produces in an allotment garden can show serious deficiency symptoms in a hydroponic system with the same pH and optimal Ec value - and vice versa. There is no way around testing and closely observing the plant depending on the chosen nutrient composition.

The pH and EC values ​​are the most important things in hydroponics. Every plant has a unique pH and EC value. In order for it to thrive, they must be in an ideal area. You can measure these values ​​using either test strips or a digital meter.

The pH value indicates how acidic or basic a nutrient solution is. The values ​​are defined on a scale from 0 (acidic) to 14 (alkaline). 7 is pH neutral. The pH value of the nutrient solution influences the availability of the nutrients. Some nutrients are more readily available under alkaline or acidic conditions. Since every plant has different nutrient requirements, every plant in hydroponics has its optimal pH value.

The EC, PPM, CF (Electrical Conductivity) value, on the other hand, describes the electronic conductivity of a solution. This provides information about the amount of dissolved salts. Nutrients break down into ions. The ions conduct electricity due to their positive and negative ions. The more conductive the nutrient solution is, the more nutrients are present in the nutrient solution. Some plants prefer a high concentration of nutrients and some prefer a low one. Too many nutrients are toxic. Too few nutrients lead to deficiency symptoms. This value alone has no meaning as to the necessary composition of the fertilizer. See the article about fertilizer.

You can have the following list interactively filtered here or download it completely.