The Right TDS Level For Hydroponics

What is the TDS level? Standing for Total Dissolved Solids, TDS is a measurement for the dissolved content, including organic and inorganic substances in a liquid.

The TDS level is usually applied to freshwater systems to check their water quality, like lakes, rivers, and streams. Moreover, small freshwater systems also use it, for example, TDS level for hydroponics. 

The solids are not considered pollutant but chemical contaminants that decides how drinkable the water is.

In the case of hydroponics, TDS is mainly used to indicate plant nutrient availability. It helps the farmers control the nutrients to boost the plant’s growth.

If water lacks or has too many certain nutrients, farmers can take some action to balance the water.

Understanding the TDS level is also important to provide the right amount of nutrients for each plant’s growth phase as each phase requires different nutrients.    

EC, PPM, and TDS levels for hydroponics

The unit to measure TDS is Parts Per Million (PPM). Besides knowing the TDS level for hydroponics in PPM, hydroponic farmers should also know the Electrical Conductivity (EC).

Pure water (H2O only) cannot conduct an electrical current. Yet, when the water contains mineral salts and other nutrients dissolved in water, they give electrical properties and change the water to become a good conductor.

The conductive minerals can be measured in Siemens-per-meter.

EC and TDS are closely related to hydroponic farming. Since the mineral salts define the EC and mineral salts are also one of the measured components in TDS, people could convert the EC to TDS level and vice versa.

To do the conversion, people usually use table conversion or the formula.

How to measure TDS level for hydroponics

There are several ways to measure the TDS level for hydroponics. The accurate one is by evaporating the water and counting the residue.

For simplicity, hydroponic farmers mostly use handheld TDS/EC meters. In some products, TDS meters are EC meters with automatic conversion.

However, different products use different conversion factors. It creates inconsistent and different results. Hence to get an accurate measurement is by sticking to the EC measurement. The steps of using TDS meters are easy as follows:

  • Open the cap off the probe end if there is any.
  • Turn on the meters by pressing the button or the switch.
  • Put the probe into water, or you can take the water into the cap and then stick the probe into it.
  • Wait until the final numbers appear and stay for a few seconds.
  • Read the number. The measurement unit is PPM.

Proper TDS level for hydroponics

Just like humans, plants also take a different amount of nutrients. There is no single right measurement that fits all plants. For vegetables and fruits, here is the list of proper TDS levels for hydroponics in PPM from the highest to the lowest.

Broccoli                                                                       :1960-2450 (PPM)

Eggplant                                                                      :1750-2400

Cabbage, Brussel Sprouts                                          :1750-2100

Tomato, Pepper                                                           :1400-3500

Bean                                                                            :1400-2800

Potatoes                                                                      :1400-1750

Endive, Okra, Mint                                                     :1400-1680

Cauliflower                                                                 :1280-1400

Beets                                                                           :1260-3500

Pumpkin, Turnip, Zucchini                                         :1260-1680

Spinach, Chives, Strawberry                                      :1260-1610

Celery, Blueberry                                                       :1260-1400

Carrots                                                                        :1120-1400

Asparagus, Garlic, Leek, Onions, Peas, Parsnip       :980-1260

Artichoke                                                                    :860-1260

Sweet Corn                                                                 :840-1680

Radish                                                                         :840-1540

Sage, Rosemary, Basil                                                :700-1120

Thyme, Parsley                                                           :560-1120

Lettuce                                                                        :560-840

Tips for maintaining the right TDS level for hydroponics

Once the right amount of nutrients has been set up, the nutrients might get reduced or added naturally. This will influence the plant’s growth. So to maintain the TDS level for hydroponics and the nutrients, here are several things you can do.

  • Get a good EC/TDS/Quality meter. As the temperature influences the EC level, some meters cannot handle or give an accurate level in water with certain degree temperatures. The goof one should handle extreme temperatures well.
  • Always clean up the meter after using it. Cleaning can be done by rubbing distilled water and/or a calibration solution matching the meter’s conversion factor.
  • Add or replace the water after checking weekly, if needed. You should take action considering the measurement.
  • For the base of the nutrient solution, use distilled water or reverse-osmosis filtered one.

Effects of wrong TDS level for hydroponics

As stated before, each plant has its ideal TDS level for hydroponics. Other numbers (less or more) might bring damage to the plant.

Excessive nutrients usually lead to yellowing of the edges and tips of leaves. They will turn brown, dried, and brittle for a longer time.

Moreover, the abundant nutrients also make thickened roots, dull and bent leaves, wilting stems, and slow growth.  

Meanwhile, lacking nutrients cause similar conditions, but the color change starts from the center first, not the edges. Other symptoms include stunted leaves and roots, holes in leaves, disproportion or twisted leaves, and brown necrosis spots.

Excessive TDS levels should be treated by adding more pure water, and lacking TDS levels can be solved by adding more nutrient solutions or using a new and better one.

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