Understanding and Measuring PPM in Cannabis Growing

Growing cannabis is an exciting but challenging pursuit. If you’re looking to maximize your harvest, you’ve likely encountered some common problems. Whether you’re dealing with nutrient imbalances, slow growth, or underperforming plants, getting your feeding schedule right is crucial.

Here is the problem: It’s easy to overcomplicate things. Knowing exactly how much of each nutrient your plants need at any given growth stage can feel like a guessing game. But here’s the good news: there is a simple solution that can take the guesswork out of nutrient management for you. That is PPM (Parts Per Million).

This helps you determine the amount of nutrients and dissolved solids in your plant’s water, allowing you to adjust your feeding routine accordingly. This article will explain the basics of PPM, why it’s essential for cannabis plants, how to measure it, and how to adjust your nutrient solutions for each growth stage.

What is PPM?

PPM stands for Parts Per Million, a unit of measurement used to determine the concentration of nutrients and minerals in water or nutrient solutions. In cannabis cultivation, TDS (Total Dissolved Solids) measures the concentration of dissolved solids in water.

So, what is TDS exactly?

Think of TDS as everything that’s dissolved in your water. It can be minerals such as calcium, magnesium, or potassium and essential nutrients such as nitrogen and phosphorus, which your plants require to grow. On the other hand, some may not be good for your cannabis plants, including salts and contaminants. They all add up to a contribution in TDS, and PPM is used as the unit of measure.

With this, you are taking a snapshot of the quantity of dissolved solids in the water. The PPM tells you if your nutrient mix is concentrated or diluted. If the PPM is too high, it might be overfeeding the plants, which can be very detrimental to the plant’s health, potentially leading to nutrient burn; this is when the plant exhibits symptoms of excess nutrients like browning tips or stunted growth. On the other hand, if the PPM is too low, your plants are not receiving enough nutrients, leading to deficiencies and poor growth.

Now that we know what TDS and PPM are let us understand why they are so important.

Why is PPM Crucial for Cannabis Cultivation?

PPM, or Parts Per Million, is one of the most critical measurements in cannabis cultivation because it directly affects plant health, nutrient uptake, and growth. Here’s why:

Nutrient Balance: PPM helps ensure your nutrient solution is well-spent and robust. Too much nitrogen can lead to weak, lush growth, while too little can cause stunted growth and yellowing leaves.
Preventing Toxicity and Deficiency: Cannabis requires fewer nutrients during early growth but more as they mature. You need to monitor PPM to avoid toxicity (too many nutrients) or deficiencies (too few), which can damage plants and reduce yield.
Fine-Tuning Feeding: PPM is a guide for feeding adjustments. By measuring and adjusting PPM regularly, the plants will receive the right amounts of nutrients at each growth stage.

Now that we know the importance of PPM, let us discuss its connection with TDS.

How PPM Relates to TDS (Total Dissolved Solids)

TDS is a measure of all the dissolved substances in your water. The higher the TDS, the more concentrated your nutrient mix is. In cannabis cultivation, high TDS readings can indicate a highly nutrient-dense solution, which may be necessary during certain stages of growth (like vegetative or flowering). However, the key is to avoid excessive TDS levels, which can overwhelm your plants and cause nutrient imbalances.

We measure this in PPM, which is defined as one milligram of dissolved substance per liter of water or one part of dissolved solids per one million parts of water. This enables you to get accurate readings about nutrient levels in your water and keep it in balance.

How PPM Affects Nutrient Absorption

Cannabis plants require a sensitive balance of nutrients to survive. These nutrients are absorbed from the water and delivered to the plants through their root systems. However, there is a catch: too much of certain dissolved solids can throw off this balance, causing absorption problems.

High PPM and Overwhelming the Roots

When PPM is too high, the mineral and nutrient solution becomes so rich that it is difficult for the plant roots to absorb the right balance of nutrients.

1. Nutrient Burn: In high-PPM conditions, plants can also undergo a nutrient burn, resulting when the plants “overdose” on the nutrients. Symptoms include the following:

Yellowing leaf tips
Brown edges
Crispy, dried-out leaves.

2. Osmotic Stress: High PPM induces osmotic stress on the plant. Osmosis is a process through which water enters the roots to dilute the concentrated solution. This leads to:

Dehydration of the plant
Nutrient toxicity due to an overload of dissolved solids

3. Salt Build-Up: High PPM can cause salt build-up in the root zone. Salts left behind by dissolved nutrients over time can:

Block water and nutrient uptake
Cause problems in the root system, particularly in hydroponic or soil-less growing methods

4. Resulting Problems: High salt buildup and nutrient overdose can lead to:

Lack of plant growth
Poor uptake of nutrients
Weakened, unhealthy plants

Low PPM and Nutrient Deficiencies

Low PPM means the water is too diluted, and the concentration of essential nutrients (such as nitrogen, phosphorus, potassium, calcium, and magnesium) needs to be higher to feed the plant.

1. Signs of Nutrient Deficiency

Yellowing leaves: A very common sign of nitrogen deficiency, which is necessary for chlorophyll production and overall plant health.
Slow growth: Without adequate nutrients, the plants will grow more slowly or show stunted growth patterns.
Poor flower production: In case of low PPM during flowering, the development of the buds will be weak; trichomes will be less dense. Flowers will become less.
2. Effect of Low PPM on Flowering and Trichome Development

Low PPM may affect your plant’s ability to produce optimal bud density and trichomes, a critical factor for potency and quality.

3. Disrupts Internal Plant Process

Healthy cannabis plants depend on nutrients for essential processes such as photosynthesis, energy production, and cell division. It causes:

Nutrient Deficiencies: Nutrient deficiencies in the elements N, P, and K will cause stunted growth and reduced bud development.
Osmotic Imbalance: Affects water and nutrient uptake, impacting metabolic functions.
Reduced Chlorophyll Production: Low magnesium or iron decreases the efficiency of photosynthesis.
Weak Root Development: Poor root health limits water and nutrient absorption.
Impaired Enzymatic Activities: Missing micronutrients impede growth-regulating enzymes.

Now that you know how vital PPM is to plant growth, let’s talk about why regular testing is so crucial.

Why Regular PPM Testing is Essential

Cannabis plants undergo several distinct growth phases, including seedling, vegetative, and flowering. Each of these phases requires a different nutrient balance. As your plants grow and develop, their nutritional needs change — what worked at the seedling stage won’t be enough during the flowering phase. Regular PPM testing allows you to stay on top of these changes and make adjustments as needed.

Adjusting Nutrients in Real Time: PPM testing will help fine-tune the nutrient levels for each growth stage. The levels are lower for seedlings, higher for vegetative, and specific for flowering to support bud production.
Prevention of Problems Early: Regular PPM checks catch nutrient imbalances early, allowing you to adjust before issues impact plant health.
Adapting to Environmental Changes: Environmental factors can affect nutrient absorption. Regular PPM testing helps adjust the nutrient mix to what your plants need according to changing conditions.

Are you worried about tracking nutrition levels in real time? Don’t worry. PlanaCan makes it easy to track your growth in cannabis cultivation. It provides automated tracking capabilities, data reports, and task management, all designed to keep you on top of the process’s most minute details.

So, what are the tools that help you measure the PPM of your cannabis plant?

Understanding Measuring Tools: TDS and EC Meters

The most common instruments used to measure PPM are the TDS and EC meters. Although they measure nutrient concentration, they work differently. Understanding these differences and how these tools work will help you choose the right instrument for your growing setup.

Purpose of TDS Meters in Measuring PPM

Most cannabis growers use a TDS (Total Dissolved Solids) meter to measure the concentration of nutrients dissolved in the water. Essentially, the TDS meter measures the amount of dissolved solids in the solution, including nutrients, salts, and minerals. These particles affect the way the plant absorbs nutrients and water, so it is essential to track their concentration.

The TDS meter works based on the electrical conductivity of a solution. Here’s how it works in a nutshell:

The meter passes a little electric current through the water.
The resistance to the water current faces while passing through is proportional to the number of dissolved particles in the solution.
The more particles at a given moment, the more resistance, the higher the PPM reading.

Purpose of EC Meters in Measuring PPM

Electrical conductivity is a critical measure of the nutrient concentration in your solution.

EC is the measure of the ability of water to conduct electricity. Conductivity depends on the TDS (total dissolved solids), such as salts and minerals, dissolved in water. More dissolved solids mean more conductivity.

Essentially, EC is the principle by which the concentration of dissolved solids increases while the electrical flow increases in water. Thus, an EC meter reads this conducting property and reports it back as micro siemens per centimeter (µS/cm). The higher the value, the higher the concentration of dissolved particles in the nutrient solution.

The only difference between EC and PPM is the unit of measurement. EC meters are typically measured in micro siemens per centimeter (µS/cm), representing how well the solution conducts electricity. Since most cannabis growers use PPM to manage nutrients, it’s often necessary to convert EC readings to PPM.

EC to PPM Conversion

EC values can then be converted to PPM using conversion factors, which are usually 500 or 700, depending on the meter’s calibration.
For example, if your EC meter reads 1.5 EC (1500 µS/cm) and you use a 500 conversion factor, you multiply the EC value by 500 to get the PPM (1.5 x 500 = 750 PPM).
Why are the conversion factors different? This is a matter of how each manufacturer calibrates the EC meter. A factor of 500 is typical in the United States, but 700 is more prevalent in Europe and elsewhere.

Now that you have some idea about the EC Meters and the TDS Meters, let us compare the two to help you choose better for your cannabis plant.

Comparison Between TDS Meters and EC Meters

Both TDS meters and EC meters measure the concentration of nutrients and dissolved solids in your nutrient solution. However, there is a difference that may make one more appropriate to your needs than the other.

TDS Meters:

Direct readings in PPM: TDS meters are set to read directly on PPM, which is the standard measurement for cannabis growers.
Ease of use: These involve fewer steps and are usually more user-friendly. Choose a TDS meter if you want a rapid answer without converting units.
Affordability: TDS meters are usually less expensive and more affordable than EC meters, making them effortlessly appealing to new growers who start or have smaller operations.

EC Meters:

More detailed readings: EC meters give readings in micro siemens per centimeter (µS/cm), which can be more precise for experienced growers who are dealing with complex solutions.
Conversion required: Although EC meters do not measure PPM directly, the conversion is simple, and many growers like the added control this provides.
Advanced control: EC meters enable more precision when dialling in nutrient levels, which is ideal for growers who experiment with various formulas or are trying to reach a target nutrient.

Now that you have clarity about what to choose to measure and manage the PPM levels in your cannabis let us understand the ideal PPM levels needed in each cannabis growth stage.

Recommended PPM Levels for Cannabis Growth Stages

Understanding the ideal PPM levels for your cannabis plants during each growth stage is critical to ensuring their health and maximizing yield. The right nutrient concentration helps your plants thrive without the risk of overfeeding or deficiencies. Let’s break down the ideal PPM levels at each stage of the cannabis life cycle:

1. PPM Requirements During the Seedling Stage

The seedling stage is the first growth stage of cannabis, which generally lasts for 1 to 3 weeks after germination. Here are some of the requirements of this stage:

Ideal PPM for Seedlings: The ideal PPM range for seedlings is between 200 and 400 PPM, which provides the right balance of nutrients for young plants.
Why This Range?: Seedlings require minimal nutrients at this stage. Too high a concentration can cause nutrient burn, resulting in yellowing leaves, curling tips, and stunted growth. Their delicate root systems aren’t yet capable of handling high PPM levels.
Diluted Nutrient Solution: During the seedling stage, it is recommended to use a significantly diluted nutrient solution—typically a quarter-strength mix of your regular feeding schedule. This provides the necessary nutrients without overwhelming the young plants.

Pro tip: If you’re growing in hydroponics, monitor the water’s PPM levels daily, as the concentration can fluctuate quickly. On soil, the PPM is more stable but should still be kept low.

2. PPM Requirements During the Vegetative Cycle

As cannabis grows into the vegetative cycle, it expands rapidly in terms of size and structure. Here are some of its requirements:

Ideal PPM Range: The ideal PPM range of 500–800 ensures that these nutrients are available in the correct concentration to meet the plant’s increased demand.
Why This Range? During the vegetative stage, plants require nitrogen for leaf and stem growth, phosphorus for root development, and potassium for overall plant function. This PPM range provides enough nutrients for healthy growth without the risk of overfeeding.
Increased photosynthesis: It occurs when plants start photosynthesizing at a faster rate. Adequate nutrients are needed to produce chlorophyll, which provides energy for further growth.

Pro tip: Ensure that the plant has enough nitrogen, as this is essential for good, healthy foliage. A sufficient supply of phosphorus and potassium is also required for a stem to thicken up and support subsequent bud development.

3. PPM Requirements in the Flowering Stage

When cannabis reaches the flowering stage, its nutritional demands change to support bud formation. Here’s what is needed:

Ideal PPM Range: Depending on the strain and environmental factors, the perfect PPM range for this phase typically ranges between 800 and 1,200 PPM.
Phosphorus and Potassium Requirements: The plant needs a higher amount of phosphorus to support flower formation during flowering. Potassium is required to strengthen cell structure and aid sugar production in the buds.
Avoid Excessive Nitrogen: Too much nitrogen during flowering can lead to poor bud development, delayed flowering, or even hermaphroditism when the plant produces both male and female reproductive organs.

Pro tip: You can reduce the amount of nitrogen in the nutrient mix during the flowering stage to shift the plant’s focus from leafy growth to producing quality buds. Ensuring that the PPM is within the optimal range helps maintain the nutrient balance without overwhelming the plant.

Now that you have an idea about PPM levels, let’s discuss how to use a TDS meter to measure them.

How to Measure PPM Using a TDS Meter

A TDS meter is a simple and effective tool to measure the Parts Per Million (PPM) of dissolved solids in your nutrient solution. Here are the steps on how to measure PPM using a TDS meter:

Prepare your Nutrient Solution: If you are using water with nutrients, make sure it is well-mixed. For a hydroponic reservoir, stir the solution well so that the nutrients are completely dissolved.
Calibrate Your TDS Meter: Calibration is necessary for accurate readings. Refer to the manufacturer’s instructions for calibrating your meter using a calibration solution with a known PPM value. It is recommended that you recalibrate your TDS meter every few weeks to maintain consistent accuracy.
Immerse the TDS Probe in the Solution: Insert the TDS probe into the nutrient solution. Make sure it is fully immersed but not touching the sides or bottom of the container, as the probe measures the electrical conductivity of the liquid.
Wait for the Reading to Stabilize: Wait for a few seconds for the TDS meter to stabilize and display the reading, which will indicate the concentration of dissolved solids in PPM.
Record the PPM Value: Once the reading stabilizes, record the PPM value and compare it to the ideal PPM range for your plant’s current growth stage (seedling, vegetative, or flowering) to see if any adjustments are necessary.

Interpreting PPM Measurements and Making Adjustments

After you have the PPM reading, it’s important to interpret it correctly in the context of your plant’s needs. Here’s how to interpret the readings and what to do next:

1. Check if the PPM is Too High or Too Low:

Too High PPM: Indicates an overly concentrated nutrient solution, potentially leading to nutrient burn or osmotic stress.

Tip: Dilute with more water to lower the PPM to the ideal level.

Too Low PPM: Indicates insufficient nutrients for your plants, which can lead to deficiencies, stunted growth, and yellowing leaves.

Tip: Add more nutrients to increase the PPM to the desired level.

2. Consider the Type of Water You’re Using: Dissolved solids exist in tap water. High PPM readings, often in hard water areas.

Tip: Adjust nutrient concentrations based on your water’s baseline PPM—less concentrated nutrients are needed for high-PPM water, and more nutrients are needed for low-PPM water.

3. Adjusting Nutrient Concentration

To Increase PPM: Add more nutrients and mix well. After a few minutes, re-check the reading.
To Decrease PPM: Dilute it further with water and re-check whether it falls within the appropriate range.

4. Monitoring Over Time: The nutrient solution should constantly be tested, especially if the plants seem stressed. Hydroponic setups should have daily checks to stay within the optimal ranges for every stage of growth.

Do you want to automate this process? PlanaCan generates and stores detailed reports for each harvest. Over time, these reports reveal trends, enabling growers to make informed decisions and improve their processes to obtain higher yields consistently. Contact us to learn more about our purpose-built cultivation software.

Next, let us understand how to manage runoff PPM, which is just as important as keeping track of your nutrient solution.

Managing Runoff PPM and Addressing Nutrient Uptake Issues

Runoff is the amount of water that drains from the bottom of your pots after watering or feeding. It’s a beneficial measure of how well the plant is taking up its food and indicative of potential nutrient uptake issues. Monitoring runoff PPM helps ensure that plants are neither overfed nor underfed and alerts one to the buildup of salts and other nutrient imbalances in the system.

Measuring Runoff PPM/EC

The process of measuring runoff PPM is similar to measuring the PPM of your nutrient solution but requires you to collect the water that has drained from the pot after watering. Here’s how you can do it:

Water Your Plants: Water your plants heavily using the nutrient solution, which drains from the bottom of the pots.
Collect the Runoff Water: Place the runoff in a clean container or tray. You only need a small amount for testing.
Test the Runoff with a TDS Meter: Use your TDS meter (or EC meter) to read the runoff PPM, which is the concentration of dissolved solids leaving the pot.
Interpret the Runoff PPM: The runoff PPM should be lower than that of the nutrient solution. A runoff PPM much higher or lower than that of the nutrient solution calls for an adjustment in your feeding schedule.

Correcting High or Low Runoff PPM

Once you’ve measured your runoff PPM, interpreting the results is the next critical step. Here’s what to do if the runoff PPM is higher or lower than expected:

High runoff PPM: Suggests Nutrient Buildup or Salt Accumulation

It is an indication that the plants are not uptaking at the correct rate, leading to excess salt buildup in the root zone. This is how to correct the issue:

Flush the Plants: Use clean, pH-balanced water to remove excess salts and dissolved solids. To ensure proper flushing, use 2-3 times the pot size.
Monitor PPM During the Flush: Measure runoff PPM as you are flushing. The PPM should decrease. Once it stabilizes at a lower level, it is good and indicates successful flushing.
Adjust Your Feeding Schedule: After flushing, reduce the nutrient concentration in subsequent feedings to avoid salt buildup. Water at a lower PPM and adjust your fertilizer application relative to your plant’s growth stage.

Low Runoff PPM: Indicates Insufficient Nutrient Uptake

If the runoff PPM is too low, your plants are not absorbing as many nutrients from the solution. A weak concentration could cause this because the roots fail to feed the plant nutrients. Here’s what you can do:

Increase Nutrient Concentration: If your runoff PPM is low, then your plants need a nutrient increase. Gradually increase the PPM to avoid nutrient burn and monitor the plants’ response.
Ensure Proper Watering Practices: Running water Low PPM can also result from inadequate watering. Water thoroughly until excess runoff appears to ensure even nutrient distribution.
Check for Root Issues: Persistent low runoff may indicate root problems, such as poor health or compaction. If the plants are root-bound, ensure good soil aeration or transplant them.

With everything in place, now let’s understand why the monitoring of PPM in tap water is so important.

Why is Monitoring Tap Water PPM Essential?

When it comes to adjusting your nutrient solution, take note of the impact of your tap water. Tap water contains minerals and dissolved solids that contribute to the total PPM reading, and these dissolved solids need to be factored into your overall nutrient mix. Here’s why monitoring tap water PPM is crucial:

Tap water contributes to the overall PPM: Even clean-looking tap water contains minerals such as calcium, magnesium, and sodium, which affect the overall PPM. When nutrients are added, a high tap water PPM (for example, 150-200) can push the overall PPM too high, stressing your plants.
Test Your Tap Water: Before adding nutrients, test your tap water’s PPM with a TDS meter. Subtract the tap water PPM from the total PPM after adding nutrients to see how much you’re actually adding to the solution.
Adjust Your Nutrient Mix: If your tap water has a high mineral content, reduce the nutrient solution. For low PPM water, add more nutrients to reach the optimal range for your plants.
Monitor pH and Water Hardness: Check on your tap water pH and hardness – these affect nutrient uptake. Hard water may require pH adjustments, while soft water needs added calcium.

Conclusion

In cannabis cultivation, regularly monitoring PPM is important for maintaining healthy plants and optimizing nutrient uptake. By measuring both your nutrient solution’s PPM and runoff’s PPM, you can identify nutrient imbalances early on and make adjustments to keep your plants thriving. Understanding the PPM of your tap water also helps you tailor your nutrient mix for the best results.

With tools like PlanaCan, growers can easily track and adjust PPM in real-time, making nutrient management simple and improving plant health. It doesn’t matter if you’re just starting or a seasoned cultivator; the key to a successful harvest is keeping an eye on your PPM levels.

Schedule a free call today to learn how PlanaCan can help you better manage your PPM and optimize your cannabis cultivation process.