What is TDS and Why Does It Matter When Growing Cannabis?

Nutrients are like food for your cannabis plant, but what happens if you can’t see how much of it you are feeding your cannabis plant? It can create some problems. Your plant can either starve or consume too much, both of which can be bad for your plant’s health. 

So, how do you avoid this, and do you need to send your nutrient solution to a lab to test it every time? Not really. The answer lies in TDS. In this article, learn everything you need to know about TDS when growing cannabis plants. 

But, before we talk about the TDS, let’s first understand why water quality is so important to grow cannabis. To put it simply, if you don’t start with good water, you’ll simply be chasing problems throughout the life cycle as it has an impact, on the health, growth, and overall yield of the plants. 

The quality of water you use determines whether the plants can even absorb the nutrients you provide or not. And, as nutrients are food for plants, you can bet that they won’t grow well if you don’t pay attention to the water. Here’s a quick overview of why water is important. 

1. Nutrient Absorption

Water plays a big role as a carrier of nutrients. Essentially, it’s the medium through which minerals and nutrients are transported to the roots of the plants. The quality of water determines how well these nutrients dissolve and become available for absorption, ultimately affecting how efficiently they are taken up by the plants.

2. pH Balance

The quality of water is closely linked to pH levels which are critical for absorption. Cannabis plants thrive within a specific pH range. While it should be between 5.5 to 6.5 for hydroponic plants, it should be about 6 to 7 for plants growing in soil.  Any drastic deviations can lead to deficiencies or toxicities in nutrient levels. Maintaining water quality helps stabilize pH levels and create an environment that promotes optimal nutrient uptake.

3. Avoiding Salt Accumulation

The quality of water is closely connected to Total Dissolved Solids (TDS) which measures the concentration of minerals and salts. Poor water quality with inappropriate TDS levels can result in salt accumulation within the growing medium and hamper nutrient absorption. 

4. Promoting Healthy Microbial Activity

Clean water supports microbial activity within the soil or growing medium. A balanced microbial ecosystem assists in maintaining strong roots that make the plant strong. Poor water quality can disrupt this balance leading to issues such as root diseases.

To put it simply, water quality forms the foundation of thriving cannabis cultivation. If you understand the basics of it, you can manage it effectively to create an environment that aids with excellent nutrient absorption, reduces contamination risks and ultimately leads to the production of top-notch cannabis buds.

What is TDS or Total Dissolved Solids? 

TDS or Toral Dissolved Solids measures the combined presence of both organic substances in water in a dissolved state. Meaning, it’s a number that represents the concentration of solids that include inorganic and organic compounds. 

To measure the amount of nutrients and minerals present in the water or the nutrient solution, you can either check TDS or EC. The former stands for total dissolved solids and the latter stands for electric conductivity. 

Both these measurements focus on the same thing but differently; TDS measures the amount of solids dissolved in water whereas EC measures the same via testing the electric conductivity. 

However, EC has one flaw — it does not detect some non-saline elements present in the nutrient solution. This is where TDS comes into play. This measurement gives you a more comprehensive reading of the nutrient solution. 

Essentially, TDS measures the amounts of salts and minerals, both ionic and non-ionic, that are present in the nutrient solution. Of course, you don’t know which specific minerals and nutrients are present in the solution, but this generic reading is more than enough for most growers.

TDS is measured in parts per million or PPM, which, as the name suggests, measures the concentration of minerals as parts present in a million part water. 

But why is TDS important for cannabis? TDS comes in handy to help you understand how much nutrients and minerals are already present in the nutrient solution and how much you should or shouldn’t add to it. 

For example, if your drinking water contains anything more than 500 mg/L of TDS, it is unsafe for consumption, according to the US EPA. Similarly, even highly concentrated nutrient solutions can be detrimental to your cannabis plant. 

If the water contains over 1000 mg/L of dissolved salts, it is unsafe for your cannabis plant. It can cause several conditions in your cannabis plant, including nutrient toxicity, nutrient lockout, nutrient burn, and much more, resulting in stunted growth, diseases, and reduced yield. 

Here’s a brief overview of the components contributing to TDS in Water:

• Minerals and Salts:

Water, regardless of the source, usually contains minerals like Calcium (Ca) Magnesium (Mg) Sodium (Na), and Potassium (K) that significantly contribute to TDS levels. They also provide nutrition to plants. However, they should be balanced as excessive amounts of any of these nutrients can cause problems. 

• Carbonates and Bicarbonates:

Ions like carbonates and bicarbonates are usually found in hard water and can increase the alkalinity. If alkaline levels rise unchecked, the pH numbers can go out of whack. And, when the pH goes out of balance, your plants will suffer. 

• Sulfates

Sulfates are another type of ion that may be present in water sources. They can not only affect the TDS but also the taste of the water. In addition, they can influence how the plants absorb nutrients. 

• Chlorides

Typically, chlorides are present in tap water. Although small amounts are necessary, excessive levels can harm the plants and even affect the flavor of the buds. 

• Organic Matter

Organic matter including acids, sugars, and other compounds that come from decaying plant material, algae, or other sources can add to the dissolved solids in water. 

• Metals

Water may contain small amounts of metals like iron, manganese, copper, and zinc that affect the TDS. These metals are important as they serve as micronutrients for plants. 

Having a detailed understanding of these elements is not necessary to grow cannabis as you don’t have to use them individually to alter the TDS. However, a basic understanding will help you ascertain the water quality and create the best environment for your plants to grow. 

What Does TDS Mean for Different Gardening Setups?

What is TDS like for common cannabis plant setups? This aspect depends on various aspects of the garden, including the type of water and the growing medium used. Let’s take a look at them here. 

TDS of Tap Water

Many cannabis growers use regular tap water to irrigate their plants. Here, if your cannabis plant has a high PPM of dissolved salts, you don’t need to add many nutrients to it; it is already loaded. 

Generally, your tap water should not have more than 500 PPM, as this is when salts and heavy metals can affect the electric conductivity of the plant. This can make it difficult to balance the nutrients in the water. Remember, if the water is unsafe for you, it is likely unsafe for the plant, too. 

Depending on the quality of tap water at your home, consider processing the water through an RO machine. Reverse osmosis is terrific at bringing down the water PPM to as low as 10 PPM, so you can add nutrients as per your plant’s needs. 

Of course, RO filtering can be expensive. In such a case, you can also use carbon filters or distillation techniques. 

You can go a step further and contact your local water supplier. Ask for a detailed breakdown of the salts and minerals content of the water — most suppliers have it at hand.

TDS for Growing in Soil 

Most growers don’t need to measure the PPM of their soil since there is less risk of overfeeding your plant here. However, depending on the soil’s quality, you can still measure the EC of the soil and convert the readings to TDS to understand the soil better. 

If you are using cheap or low-quality, non-enriched soil, you should measure the runoff water to understand whether the soil is loaded with nutrients or not. If not, you now know that you need to enrich the soil with fertilizers or supplements so that the soil can sustain your cannabis plant. 

TDS for Hydroponics 

On the other hand, if you are growing cannabis with a hydroponics setup, the importance of measuring the TDS cannot be overstated. The substrate lacks any minerals, so you need to focus here. 

In a hydroponic setup, the roots of your plants are directly in contact with the nutrient solution. As a result, your plants respond immediately to any inputs. Plus, the roots are sensitive. 

If the TDS is not right in your hydroponic cannabis plant, your plant can face problems quickly and more severely. In severe cases, your plant may even stop growing properly and the yield can also get impacted. 

What is the Ideal TDS Level for Growing Cannabis?

Let’s address the most important question of this article — how much TDS does your cannabis plant need? 

Here is a general guideline on the levels of TDS you should aim for with your nutrient solution or tap water during each stage of your plant’s growth. The numbers are measured with a Hanna 500 PPM EC meter. 

• 500 to 600 PPM for seedlings
• 800 to 900 PPM for the vegetative stage 
• 1000 to 1100 PPM for the flowering stage 
• 400 to 500 during the pre-harvest or late-flowering stage 

Remember to check the TDS of your nutrient solution, especially if you are cycling it through a reservoir in a hydroponic setup. As your plant consumes nutrients, the TDS of the reservoir water can dip after a few days. 

Here's what you can expect based on EC measurements:

• Stable EC 

When your EC measurement remains constant, it indicates a well-balanced ratio of water to nutrients. To maintain this balance, you can add a nutrient solution of the same strength to the reservoir as a top-up. Monitor the EC constantly to maintain these levels. 

• Low EC 

A low EC reading suggests that the plant is using more nutrients compared to water. For this, add a solution that’s slightly more concentrated, depending on the reading. 

• High EC Measurement

Conversely, a high EC reading suggests that your plant is using more water compared to the nutrients. To overcome this imbalance, you can add a solution that’s less concentrated or a solution with more water. 

Be, on the lookout for signs such as burnt tips on leaves and slow plant growth, which could indicate that your nutrient solution is too strong. Also, consider the weather conditions because plants tend to absorb extra on hot days. 

Additionally, high-quality nutrients come with a TDS chart that you must go through. Compare the chart to your tap water TDS to check if you need to add more nutrients to the water or not. 

Consequences of High EC

When you see many symptoms in the plants, it can be confusing to identify whether it’s occurring due to the EC or something else. For example, even a pest infestation could cause yellowing leaves. Or, a pH imbalance could turn the leaves brown as the roots will no longer be able to absorb the nutrients properly. So, if you want to help your plants, you should be able to identify the problem in the first place. This means that you should understand a bit more about the pH, and nutrient deficiencies that could be causing the problem. 

If the EC is way too low below the recommended range, the plants may experience a deficiency in nutrients. As a result, you may notice yellowing of leaves, brown discoloration, necrosis, and stunted growth. The leaves may start twisting as well. 

Symptoms of damage due to improper EC levels are not consistent in all stages of growth. Also, you will see the first few signs on the lower leaves that then spread to the younger ones. This is because the solution contains higher concentrations of nutrients like nitrogen, phosphorus, and potassium compared to other elements. An imbalance in any of these nutrients can show such signs on the leaves. And, as the plant absorbs water it also takes up all these excessive ions that are dissolved in the solution. However, if the EC level becomes excessively high this process can lead to tissue damage or necrosis.

When the EC is high, you can spot the symptoms in new leaves as these areas undergo rapid cell division and need more water. While the leaves may display slight discoloration in the initial stages, the outer edges may also turn brown after a while. Note that the severity also depends on the level of toxicity of the nutrient solution you’re using. If you’re feeding solutions with extremely high EC levels, the leaves may suddenly turn brown and die too. 

Although young leaves display more signs, it doesn’t mean that the older leaves are safe from the effects of high EC. After a while, even the older leaves may show burnt edges where browning starts from the edges and progresses inwards. As these leaves are actively involved in photosynthesis, they take up more water, which leads to a faster accumulation of ions, resulting in higher EC. 

Most growers take immediate action when they notice that the leaves are not healthy. However, if you don’t do anything for some reason, you’ll see that the salt accumulation becomes more pronounced in lower leaves. As ions continue to build up, the leaf margins also start wilting or appear brittle and brown, and the plant may also die. 

Therefore, be proactive and check the EC levels regularly to prevent any issues. 

How to Measure TDS While Growing a Cannabis Plant?

Checking the TDS of your water while growing a cannabis plant is fairly easy, but it may take some time to get a hang of it for some growers. 

The easiest method to do this is to get a dedicated TDS meter. However, such meters can be a bit pricey. Instead, you can even use an EC meter to test the TDS of the water. All you need to do is convert the readings! 

To check the TDS of your water, use a high-quality, calibrated EC meter and test the EC of the water. Then, multiply EC by 1000 and divide by two. Congratulations, you have your rough TDS reading of the water or nutrient solution. 

Remember, such a conversion may not always be accurate; there’s usually a 10% difference between the EC readings and TDS conversions. However, such a margin produces negligible results, so don’t sweat it. 

Run-Off TDS Measurement 

Let’s go a step further and test the TDS of the runoff water too. This can further help you understand and interpret the TDS levels of the nutrient solution. So, ideally, you should measure the TDS of the reservoir water/tap water and the runoff water. 

If the runoff PPM is lower than the water you feed your cannabis plant, there’s no need to worry. It’s a sign that your plant is absorbing the nutrients. However, if the difference between the two readings is drastic, you may want to add more nutrients to the water. 

On the flip side, if the runoff PPM does not change at all, you need to start worrying. It’s a sign that the roots are not absorbing the nutrients at all. If the runoff PPM is high, you need to flush your plant and be more conservative about the nutrients since this is an indicator of salt buildup within the growing medium. 

How to Change TDS of Water or Nutrient Solution for Cannabis?

Sometimes, your water or the nutrient solution can have the wrong TDS levels. So, you will need to bring the levels down. 

You can do this by filtering the water. As mentioned above, you can use RO filters, carbon filters, or distillation to bring the PPM of the water down to ideal levels. On the flip side, if you want to increase the PPM of the water, you need to add more nutrients to the water. 

Some growers may face a problem with the water in general — it may be too high in PPM. In such cases, it is better to try out other water sources like bottled water and rainwater. See if it works for you. 

Summary: What is TDS and Why Does It Matter When Growing Cannabis?

TDS refers to total dissolved solids, and it is a measurement of the concentration of minerals and salts present in a solution. It can be measured using a TDS meter or an EC meter. 

Whichever method you use to measure it and regardless of the type of water you use, make sure the TDS levels of the solution are not too low or high. And if required, manage the levels. Your plant will thank you.