When we started learning hydroponics, the three things that confused us the most were EC, TDS and pH. But later I realised that these are actually the heart of the whole system. If we understand these three properly, plants grow beautifully without any struggle. So here is my simple way of explaining them.
1. What is EC? (Electrical Conductivity)
EC tells us how strong our nutrient water is.In simple words, it shows how many nutrients the plant is receiving.
- Higher EC means more nutrients, and lower EC means fewer nutrients.
- Every crop has its own EC requirement:
- Leafy greens need low EC
- Fruiting crops like tomato, chilli and capsicum need higher EC
If EC is too high, roots get stressed and leaf tip burn appears.
If EC is too low, plants become pale and growth slows down.
2. What is TDS? (Total Dissolved Solids)
TDS is the ppm value of nutrients present in the water.It is almost the same as EC but expressed in a different unit.
Most meters show both EC and TDS.
In hydroponics, we often use TDS to decide when to add nutrients or dilute the solution.
We recommend monitoring either EC or TDS, depending on your preference, as both serve the same purpose.
3. What is pH? (Potential of Hydrogen)
pH shows whether the nutrient solution is acidic or alkaline.
Even if EC and TDS are perfect, if pH is not correct, plants cannot absorb nutrients.
- For most hydroponic crops, the ideal pH range is 5.5 – 6.5.
- If pH is high → nutrients get locked
- If pH is low → roots get damaged
So maintaining pH is very important for healthy grow.
4. What is ppm? (Parts Per Million)
ppm means Parts Per Million. It tells us how many parts of nutrients are present in one million parts of water.
- In hydroponics ppm is an easy way to understand nutrient concentration.
For example:
300 ppm means there are 300 parts of dissolved nutrients in one million parts of water
- ppm is directly related to EC:
- Low ppm = low nutrients
- High ppm = high nutrients
That is why ppm, EC and TDS are always connected and should be checked together.
Basic EC & pH Ratios for Starting Stage
The starting stage is very sensitive, so nutrients should always be given slowly and carefully.
1. Seed Germination Stage
- EC: 0.0 – 0.4
- TDS: 0 – 200 ppm
- pH: 5.8 – 6.2
At this stage, plain water is enough.
Adding nutrients early can burn young roots.
2. Seedling Stage (After true leaves appear)
- EC: 0.6 – 0.8
- TDS: 300 – 500 ppm
- pH: 5.8 – 6.2
This is the right time to start nutrients, but only in low concentration.
Always start with low EC and slowly increase.
3. Vegetative / Leafy Growth Stage
- EC: 1.0 – 1.6 (leafy crops)
- TDS: 600 – 900 ppm
- pH: 5.5 – 6.5
Plants actively grow in this stage and need more nutrients.
EC should be increased gradually, not suddenly.
•When to Add Nutrients???
- When EC or TDS drops, it means plants have consumed nutrients → add nutrients
- When EC rises suddenly, it means water is evaporating → add plain water
- Always adjust pH after adding nutrients
•Why EC, TDS and pH Must Be Balanced
These three should always work together
- EC shows nutrient strength
- TDS shows total minerals
- pH decides nutrient absorption
If any one value goes wrong, plants immediately show stress like yellowing, stunted growth or tip burn.
I personally check EC/TDS daily and pH twice a day, especially during hot weather, because pH fluctuates quickly.
Conclusion:
EC tells us how much food the plant is receiving,
TDS tells how much mineral content is present,(Either EC or TDS can be followed, as both indicate the nutrient concentration)
and pH decides whether the plant can absorb it or not.
When EC or TDS and pH are maintained properly from the starting stage itself, hydroponic plants grow healthy, strong and give better yield with fewer problems.
Compiled and written by
Agrowvitz Agronomist
-Pallikonda Harshitha.
