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Best pH, EC, and PPM for Hydroponic Marijuana

Added 28 June 2022

Growing hydroponic cannabis is a rewarding experience, but as you gain more experience, you get immersed in a universe of knowledge. During this journey, you will come across three concepts — pH, EC, and PPM — everywhere, and these are important for you to grow a healthy cannabis plant.

Your plant requires a healthy environment to grow in, and the growing medium’s environment is perhaps one of the most important. It needs the right kind of conditions so that it can retain the nutrients and the roots can absorb them easily. 

pH, EC, and PPM are responsible for this very function — if the numbers are off, the roots will fail to absorb the nutrients properly, leading to various problems. Additionally, EC and PPM are also responsible for knowing whether the roots are getting enough nutrients or not. 

You need to monitor the pH and EC/PPM in tandem for a healthy plant, but you might be wondering how EC/PPM readings are related to the pH levels. 

Let’s say your PPM levels are ideal for good plant growth, but the pH levels are off. In such a case, the PPM readings are useless since the roots cannot absorb some nutrients due to pH imbalance. 

So, to grow a healthy plant, you must ensure the pH, EC, and PPM of your growing setup are ideal. But don’t worry, while it may seem complicated, this article is here to make it easier for you. Read this guide to know the best pH, EC, and PPM for your hydroponic cannabis.

pH Levels of the Solution and Growing Medium

pH scale

When growing cannabis, you must ensure that the nutrient solution and growing medium’s pH levels are balanced so that the nutrients can dissolve easily, making it easier for the roots to absorb them. 

The pH scale comes into action here, ranging from 0 to 14.0, and it dictates how the minerals and nutrients will interact with each other based on their ionic state. 

Essentially, pH represents the concentration of hydrogen ions in the nutrient solution. But in layman's terms, it represents the acidity or alkalinity of the solution. If the pH of the solution is under 7.0, it is acidic, if it is over 7.0, it is alkaline, and if it is 7.0, it is neutral. 

However, since pH scales work in a logarithmic function, even small changes in the pH levels can significantly affect your plant’s nutrient uptake. For instance, a pH of 7.0 is ten times more alkaline than 6.0, which can make a massive difference.

Importance of Ideal pH Levels in Cannabis

pH

The pH level for cannabis is crucial because its nutrient uptake depends on it. If the pH is too acidic, various micronutrients like iron and manganese become more soluble, which can overdose your plant with those particular nutrients.

On the other hand, if the pH is too alkaline, various nutrients, including phosphorus, become less soluble, leading to nutrient deficiency in the plant since the roots cannot absorb them properly.

So, you must ensure the right pH levels for your cannabis plant to prevent it from experiencing common problems like nutrient deficiency, lockout, or burns. Do so and your plant will utilize your nutrients more efficiently and grow vigorously.

Ideal pH Levels

hydro pH chart

Unbalanced pH is unhealthy for your plant as it makes the nutrient unavailable to your cannabis. So, you must stick to the recommended pH levels. But remember, a neutral pH doesn't mean it's right — cannabis grows best in slightly acidic conditions. 

Cannabis plants can handle pH levels ranging from 5.0 to 7.0. Beyond this range, however, they can start showing symptoms of bronzing, nutrient deficiencies, or chlorosis (leaves turning yellow), along with slower and stunted growth.

The optimal range for cannabis is 5.5 to 6.5 for hydroponic cannabis plants. Different nutrients become soluble at different pH levels. For example, calcium and magnesium get soluble over a pH of 6.0, while other nutrients get absorbed under slightly more acidic conditions. This range covers it all.

Balance your nutrient solution’s pH and you will be rewarded with a massive cannabis plant with juicy buds and astounding yields.

How to Test the pH Levels

pH tester

To ensure your nutrient solution has the right pH level, you need to test it once every few days and adjust it if needed. 

For testing the pH, you should consider investing in a digital meter, which makes testing much easier. You can also try other solutions like pH test strips or dye kits, but they are cumbersome and don’t offer an accurate reading. pH meters are far more accurate and easier to use.

Here is how you can measure the pH levels:

1. Start by calibrating the meter

caliberate the pH meter

You must calibrate the meter using a known standard. Your best bet is to use deionized RO water (since it is pH neutral). To calibrate, insert the probe into water and calibrate the display to pH 7.0.

2. Test the nutrient solution’s pH

test nutrient solution pH

Now, insert the meter’s probe into your nutrient or fertilizer solution and note down the pH readings.

3. Test the pH of the growing medium

test growing medium pH

Next, you also need to check the pH level of the growing medium since it is an electrochemical environment, which can sometimes alter the pH levels. Plus, the salt buildup can also change the pH levels drastically over time.

To test this, simply submerge the meter’s probe into the runoff water.

Once you have measured the pH levels of the solution and root zone, compare the results. The two pH readings must be similar and within the 5.5 to 6.5 range. 

How to Adjust the pH Levels

Ph-Up-Down

If the readings are outside the recommended range, you need to correct the pH. For this, you can either use pH down or pH up solutions.

pH down solutions are designed to bring down the pH levels within a solution, which is particularly necessary if you use tap water that tends to be more alkaline.

In rare circumstances, your solution’s pH may be too acidic, and you'll need to use a pH Up solution, which raises the solution’s pH levels.  

Read the manufacturer’s instructions to administer them to your nutrient solution.

You can also use other methods to adjust the pH levels. If you want to gently lower the pH levels, you can use manure, worm casting, compost, wood shavings, or pine needles. And to raise the pH, there is nothing better than lime or limestone, which you can purchase in pellet, powder, or hydrated form.

Electrical Conductivity (EC) and Particles per Million (PPM)

TDS tester

pH is just one part of the equation, the other part contains EC and PPM. And since the two are closely related, we will delve into them together.

EC and PPM are quite similar in some regards since they measure the solutes in the solution — they measure the concentration of minerals or nutrients present within the solution. 

You need to maintain the right EC and PPM within the nutrient solution to ensure your plant always gets the right amount of nutrients for vigorous growth. 

Maintaining the right EC and PPM levels also prevents other problems. If the EC is too high, it can make the singular ions present in the solution toxic for the root zone while also raising the osmotic pressure within the substrate, hindering roots’ nutrient uptake. 

On the other hand, high PPM can flood the roots with nutrients, which can cause nutrient lockout or nutrient burns, and even alter the substrate’s pH levels due to salt buildup over time. 

And low PPM or EC means that the roots are not getting enough nutrients for the healthy sustenance of the plant, leading to nutrient deficiencies, slower or stunted growth, and eventually poor yields. 

This is why you must maintain the right EC and PPM levels within your nutrient solution. Read on to know how you can do that.

What is EC?

water

Image credit - Photo by Daniel Sinoca on Unsplash 

But before we dive into the right EC/PPM levels, you must understand what exactly these terms mean for you and your plant.

EC stands for electrical conductivity, and it measures the travel time of electrical current within a solution. If the solution is rich in ions or dissolved salts, the current will travel faster, leading to higher EC, and vice versa. 

In short, electrical conductivity or EC measures the salinity in water or your nutrient solution in this case. Saline water can conduct electricity a lot more compared to RO or pure water since it contains more ions. As a result, the solution's conductivity increases.

In essence, this means that if your water has too many salts or has a high EC, it can be toxic for the plants. The toxicity of the ions can be high at the root zone and prevent the plant from absorbing nutrients.

EC is commonly measured using EC pens in millisiemens per centimeter (mS/cm), but you can also measure the same in micro siemens per centimeter (uS/cm).

What is TDS?

TDS refers to total dissolved solids in the solution. Although EC measures the saline content, not every element in the fertilizer falls under that category, which means that the non-saline molecules in your fertilizer will most likely not appear when you take an EC reading. Many growers obsess about the TDS as it provides a general reading of your solution's mineral content. But, the TDS reading is nothing but a conversion of the EC reading along with some added estimations.

A TDS reading will tell you the total mineral content dissolved in a particular sample. Although it will not tell you the number of individual salts, you get a good idea as to whether you need to increase or back off from the nutrients.

What is PPM

On the other hand, PPM stands for particles per million. It is the measurement of the number of particles present in a million parts of water, and you can look at it as a ratio of how many particles of nutrients or minerals are present in your nutrient solution.

For example, a liter of water containing 1 mg of magnesium will show a reading of 1 ppm dilution, where 1 part of magnesium makes up for a million parts of water.

In the past, if you wanted to measure your nutrient solution’s PPM, you would have to send a sample to your local laboratory. There, the technician would dry and weigh each component to measure its PPM. While this technique is super accurate, it is not sustainable for growers since it is expensive and time-consuming.

Fortunately, you can just buy a TDS meter that measures PPM. TDS meters are relatively inexpensive and you can get them everywhere.

The only downside with some TDS meters is that they may be inaccurate. This is because these meters measure the EC of the solution and then convert the readings into PPM. 

Note that manufacturers use different conversion factors, leading to different results. Some manufacturers prefer sodium chloride conversion factor, while others use 422 one. You can also find a conversion chart and do it yourself. 

EC and PPM conversion 

We recommend checking out forums and reading TDS meters’ reviews to check for their accuracy before making your purchase. A reputable TDS meter would be far more accurate than obscure ones. 

If you can’t find a reputable TDS meter, you can simply use an EC pen. They essentially measure the concentration of minerals and nutrients in the solution. 

Ideal PPM and EC Readings for Cannabis

The ideal PPM and EC ranges for cannabis plants are as follows:

Stage

PPM

EC

Clones

500-600

0.5-1.3

Seedlings

500-600

0.8-1.3

Vegetative

800-900

1.3-1.7

Flowering

1000-1100

1.2-2

Remember that not all strains are the same, so your cannabis strain may require different levels of the same. Read the seed bank’s recommendations to know the right range for your strain. 

How to Measure the EC/PPM of the Nutrient Solution

Measuring EC and PPM is quite easy, but just like measuring the pH levels, you have to test both the nutrient solution and runoff water. 

To measure your nutrient solution’s EC/PPM, follow these steps:

  1. Get an accurate TDS meter with a range of around 3,500, which is more than enough for gardening purposes; or you can use a high-quality EC meter
  2. Follow the manufacturer’s recommendations to calibrate the TDS/EC meter and ensure it is set to zero
  3. Then, insert the probe into the nutrient solution before irrigation and test the same of the runoff water after irrigation

Ensure the readings are in-line with the above recommendations. If the readings are off, you need to rectify the problem.

The runoff water should have lower EC/PPM than that of the solution. It’s a sign that the nutrient is being retained by the substrate and absorbed by the roots. If the readings are the same, the nutrient is simply draining away and your roots are probably starving mostly due to pH imbalance.

So, check the pH levels and rebalance them, and test the EC/PPM again.

On the other hand, if the runoff EC/PPM is drastically low, the nutrient solution is too diluted. You need to make it more concentrated. 

Lastly, if the runoff water has higher EC/PPM than the solution, you need to flush your plant because there is salt buildup within the root zone, where an excess of it is draining with the water. 

Water Source and PPM

RO water purifier

One essential aspect of testing the PPM/EC of your nutrient solution is knowing the same of your water source, as it can vary a lot. For instance, RO water will have a PPM of 0 to 10, tap water would be 30 to 300 PPM (as per European standards), and well water would be 500 to 700 ppm. The water will have high PPM even if the plumbing in your city is too old, due to minerals built up over time. 

You can reach out to your local water supply station to enquire about the accurate PPM of the water. 

If your water source already has a PPM higher than 500, that can be a problem. You must take the right precautions to reduce the PPM so that you don’t overwhelm your plant. For this, you can use hard water-specific nutrients or purify your water before mixing in the nutrients or fertilizers.

It is very important to choose a good water source to grow your cannabis plants. It is one of the most important decisions you will make especially while growing hydroponic cannabis.

Cultivating plants with a clean water source is critical because water helps the plant to transport nutrients, and aids in photosynthesis and transpiration as well. But, choosing a good source of water is slightly challenging, and especially hard if you're operating with a tiny budget.

There are many types of water sources you can choose from. From natural rainwater to RO, there are various ways to grow cannabis. You can even go for high-tech filtration systems, but they can be expensive. Here are a few options to choose a good water source:

Tap water

Many growers hesitate to grow using tap water, and it's easy to understand why. It usually gets a bad rep. 

Tap water is one of the most easily available sources no matter what plant you want to grow. It is cheap and although many people shy away from it, it's not so bad for your plants.

However, there's a caveat. Tap water, if it's really bad in quality, can be bad for your cannabis plants. It depends on the type of tap water that is available in your area. For example, tap water available in some locations can contain a lot of calcium magnesium, and chlorine. Cannabis needs these nutrients, but high amounts can be detrimental.

Therefore, if you're unsure about tap water, you can get it tested or leave the water under sunlight for at least 24 hours to let the chlorine evaporate naturally. You can also filter it and use it to grow plants.

Distilled water

If you don't want to take your chances with tap water, distilled water is a great option to grow cannabis plants. It contains zero contaminants and is just pure water. Distilled water is easily available in most local stores and is pretty inexpensive if you are growing just a few plants.

Rainwater

Rainwater is a great natural source to grow most plants including cannabis. However, it can be quite a task to collect rainwater if you don't have the proper equipment. Most people do not have a rainwater harvesting system setup and it can be expensive if you want to set it up just to grow a few cannabis plants. However, you can set up rainwater harvesting systems with just a few materials and collect small amounts of water but it might not be enough if you are growing even 4-5 plants at a time.

RO water

If you don't mind investing in water filtration systems then RO water is the way to go. Most water filtration systems filter contaminants effectively, making it safe to drink and grow plants.

However, the initial cost required to set up the systems can be daunting for some growers. Even the cheapest RO systems can dig a significant hole in your wallet, so make sure you have a decent budget if you want RO water to grow cannabis. 

Summary: Best pH, EC, and PPM for Hydroponic Marijuana

pH, EC, and PPM of your nutrient solution and grow media are essential and they must work in tandem with each other for healthy plant growth.

Use the guide above to test the solution's pH, EC, and PPM, and if the readings are not in the recommended range, work to adjust them quickly.

These are advanced concepts for cannabis cultivation but are crucial if you are growing a hydroponic plant. Do this and your plant will get to enjoy the nutrients and reward you with a bountiful yield.

 






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