Guide to Hydroponic Nutrient Solution

In hydroponic systems, without soil, plant growth is dependent on a nutrient solution being able to directly supply all mineral requirements via the water.

There needs to be the proper blend of macronutrients—for example, nitrogen (N), phosphorus (P), and potassium (K)—for overall plant development, flowering, and root establishment. It must also contain secondary nutrients such as calcium (Ca), magnesium (Mg), and sulfur (S), in addition to trace elements including iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), and boron (B). 

The nutrients have to be dissolved in water in appropriate quantities and properly controlled so that the plants get the best uptake. pH and EC (electrical conductivity) are two parameters of paramount importance that decide the efficacy of a nutrient solution. The optimal pH level for the majority of hydroponic crops is between 5.5 and 6.5, which provides maximum availability of nutrients.

 EC, expressed in mS/cm, is a measure of dissolved salts concentration; for the majority of vegetables, an optimal range of 1.2 to 2.0 mS/cm is recommended. Monitoring and adjustment of pH and EC levels on a regular basis are important to avoid nutrient deficiencies or toxicities.

 Properly blended and stored nutrient solutions result in more rapid growth, more robust plants, and greater yields in hydroponic crop production.

                                                           Mixing a nutrient solution

 Guide to Hydroponic Nutrient Solution

✅ 1. Nutrients that are absolutely necessary
Macronutrients (required in large quantities):
Nitrogen (N): Develops leaves and stems.
Sources: Calcium nitrate (Ca(NO3)2), Potassium nitrate (KNO3)

Macronutrients (required in large quantities):
Nitrogen (N): Develops leaves and stems.
Sources: Calcium nitrate (Ca(NO3)2), Potassium nitrate (KNO3)

Phosphorus (P): For root growth, flowers, and fruits. 

Source: Monopotassium phosphate (KH2PO4)

Potassium (K): Supports general health, water balance, and fruit growth.
Sources: Potassium nitrate, Monopotassium phosphate.

Calcium (Ca): Strengthens cell walls and stops blossom end rot.
Source: Calcium nitrate.

Magnesium (Mg): Central component of chlorophyll for photosynthesis.
Source: Magnesium sulfate (Epsom salt).

Sulfur (S): Assists in the formation of amino acids and enzymes.
Sources: Magnesium sulfate, Potassium sulfate.

Micronutrients (required in small quantities):

Iron (Fe): Necessary for chlorophyll formation.
Source: Chelated Fe (Fe-EDTA, Fe-DTPA, Fe-EDDHA)
Manganese (Mn): Activator of photosynthesis enzymes.
Source: Manganese sulfate (MnSO4)
Zinc (Zn): Growth regulation and production of hormones.
Source: Zinc sulfate (ZnSO4)
Copper (Cu): Critical to reproductive growth.
Source: Copper sulfate (CuSO4)
Boron (B): Reinforces cell walls.
Source: Boric acid (H3BO3)
Molybdenum (Mo): Assists in nitrogen metabolism.
Source: Sodium molybdate (Na2MoO4)
Chlorine (Cl): Maintains osmotic pressure. Ordinarily available in tap water.

 2. Sample Recipe for Nutrient (Per 10 Litters of Water)
Base Nutrients:

Calcium Nitrate (Ca(NO3)2): 10 g
Potassium Nitrate (KNO3): 5 g
Monopotassium Phosphate (KH2PO4): 2 g
Magnesium Sulfate (MgSO4·7H2O): 5 g
Micronutrient Blend:
Iron (Fe-EDTA): 0.5 g
Manganese Sulfate (MnSO4): 0.2 g
Boric Acid (H3BO3): 0.2 g
Zinc Sulfate (ZnSO4): 0.05 g
Copper Sulfate (CuSO4): 0.05 g
Sodium Molybdate (Na2MoO4): 0.05 g
 If available, use a pre-mixed micronutrient solution for convenience and precision.

 3. Mixing Instructions

Utilize clean water (reverse osmosis or distilled is best).
Dissolve Calcium Nitrate in 5 liters of water (Solution A).
Dissolve the remaining salts in another 5 liters (Solution B).
Pour Solution A, then Solution B into the reservoir.
Micronutrients add last, once the major nutrients dissolve completely.
Check and balance pH to 5.5 – 6.5.

Keep an eye on EC (electrical conductivity) between 1.2 – 2.0 mS/cm depending on crop.
EC (Electric Conductivity) and PPM (Parts Per Million) are both measurements of strength in nutrient solutions for hydroponics, but they are not equivalent. The conversion factor will be based on what conversion factor your EC/PPM meter uses.

What is EC (mS/cm) in Hydroponics?

✅ Definition:

EC stands for Electrical Conductivity, and it indicates how well electricity can travel through a solution. In hydroponics, this informs you about how concentrated your nutrient solution is - because more dissolved salts (nutrients) carry electricity better.

✅ Typical Conversion Factors:

EC (mS/cm)\to PPM (500 scale)\to PPM (700 scale)
1.0\t500 ppm\t700 ppm
➤ So:
1.0 EC = 500 ppm (if your meter uses the 500 scale)
1.0 EC = 700 ppm (if your meter has the 700 scale)

 Note: Always verify your meter to determine if it operates off the 500 or 700 scale (also referred to as the NaCl or 442 scale).

Would you like an easy chart of EC to PPM values over a range?
 
Here is an easy EC to PPM conversion chart for 500 scale and 700 scale meters:

EC to PPM Conversion Chart;

EC (mS/cm) PPM (500 Scale) to PPM (700 Scale):

                                                                PPM (500 Scale)  (700 Scale)    

0.2 100 ppm to 140 ppm

0.4 200 ppm to 280 ppm

0.6 300 ppm to 420 ppm

0.8 400 ppm to 560 ppm

1.0 500 ppm to 700 ppm

1.2 600 ppm to 840 ppm

1.4 700 ppm to 980 ppm

1.6 800 ppm to 1120 ppm

1.8 900 ppm to 1260 ppm

2.0 1000 ppm to1400 ppm

2.2 1100 ppm to 1540 ppm

2.4 1200 ppm to 1680 ppm

2.6 1300 ppm to 1820 ppm

2.8 1400 ppm to 1960 ppm

3.0 1500 ppm to 2100 ppm

What Is pH? :

pH is a reading of how acidic or alkaline (basic) a liquid is. In hydroponics (and soil gardening), it informs you about how efficiently plants are able to uptake nutrients from the water.

✅ Optimum pH for Hydroponics:

The majority of hydroponic crops have a preferred range of 5.5 to 6.5.

Too acidic: nutrients such as calcium and magnesium become unavailable.

Too alkaline: nutrients such as iron and phosphorus become inaccessible. 

4. Crop-Specific EC and pH Guidelines

Crop\EC (mS/cm)\pH Range

Lettuce EC  1.2 – 1.8 pH 5.8 – 6.2
Tomatoes EC 2.0 – 3.5 pH 5.5 – 6.5
Strawberries EC 1.4 – 1.8 pH 5.5 – 6.5
Spinach EC1.8 – 2.3 pH 6.0 – 7.0
Basil EC t1.0 – 1.6 pH 5.5 – 6.5

 5. Tips for Success

Always test and know your water quality.

Store nutrient solutions in cool, dark areas.

Mix and stir nutrients well before using.

Clean hydroponic systems regularly to prevent diseases.

Use quality EC and pH meters and calibrate them often.

Avoid mixing calcium nitrate with other nutrients directly—it causes precipitation.