Learn what is TDS & pH and find out how they are measured using instruments or other methods and their importance in hydroponics.
TDS means total dissolved solids in a solution. Higher concentration of solids means higher TDS and vice versa. TDS is measured by using an electronic instrument called TDS or EC meter.
EC, CF and PPM are three different units used to measure TDS or to indicate the concentration of a solution. EC means electrical conductivity, CF means concentration factor and PPM means parts per million. Higher the concentration of solids higher is the EC, CF and PPM and vice versa.
In USA 1 EC is considered equal to 10 CF or 500 PPM. In Europe 1 EC is considered equal to 10 CF or 640 PPM. In Australia 1 EC is considered equal to 10 CF or 700 PPM. So beware where your instruments are manufactured.
The value of TDS depends on 3 factors - the type of hydroponic system, the type of plant grown and the temperature of the location.
It is recommended to start with the lowest value and gradually move upwards depending on the reaction of the plant.
Plants with deficiencies can recover but a plant with toxicity is finished and beyond recovery.
Plants may require nutrient solutions with different TDS values during various stages of plant life.
pH is a unit used to measure the acidic or basic nature of a solution or mixture. It has a scale or value range of 0 to 14. Zero is maximum acidic and 14 is maximum basic. The value of 7 is considered chemically neutral.
pH is measured using a electronic meter or using litmus papers which are also call as pH test strips in hydroponics.
Red litmus paper is used to check basic nature of a solution. Blue litmus paper is used to check the acidity of a solution. Universal litmus paper is used to measure the approximate value of pH in both zones.
Most electronic meters indicate pH to accuracy of 0.1 plus minus range. Although digital electronic pH meters are ideal it is recommended to also use litmus papers occasionally. pH test strips in hydroponics are also handy there is some problem with the meter.
Plants can draw optimum nutrients from a nutrient solution only within a specified pH range. The optimum pH value differs for each plant type.
The sweet spot for most plants is around 6.5 pH value. A pH value range of 6.0 to 7.5 is okay for home growers.
To strictly stick to a narrow range of pH requires the use of chemicals to adjust pH in either direction.
Too high pH value hinders the optimum uplift of nutrients by plants from the nutrients solution.
Too low pH besides hindering the optimum uplift of nutrients also causes root rot as unwanted bacteria thrive in more acidic solutions.
Wrong pH value hinders the uplift of nutrients in the supplied proportions.
Even though the nutrient mixture is perfect the plants may not get optimum nutrients due to wrong pH value.
Some of the nutrients in a hydroponic nutrient solution are acidic in nature and others are basic in nature. The acidic ones decrease the pH and the basic ones increase the pH.
Nutrients like potassium (K), Calcium (Ca) and Magnesium (Mg) are basic in nature and therefore increase the pH. Nutrients like Nitrogen (N), Phosphorus (P) and Sulfur (S) are present in the form of nitrates, phosphates and sulfates respectively which are acidic in nature and therefore decrease the pH. The other nutrients have a very negligible effect on the pH value or variations.
Depending on which nutrient the plant draws more the pH will either increase or decrease over a period of time. If the nutrient solution is not balanced the fluctuations in pH will be large.
However there is always a minor change in pH in either direction which has to be attended to. The direction of pH variation gives a good indication as to which nutrients are used more and vice versa.
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