Water is essential for both people and plant life, with cannabis plants being no exception. Prepare yourself as we delve into water quality and understanding water’s relationship with plants. I break down all you need to know about PPM, E.C., monitoring runoff, signs of potential issues, and plenty more to help you on your way to becoming well-versed in all things water and cannabis.
TL/DR | Key Takeaways:
The optimal E.C. range for flowering hydronic plants is between 1.9-2.4
The optimal E.C. range for flowering organic plants is between 1.9-2.3
PPM refers to parts per million and is directly related to your E.C. levels.
Soft water will have 50–300 parts per million and 0.4 EC.
hard water will be between 320-420 parts per million and 0.8 EC
Rainwater will test at 500 ppm, with filtered rainwater testing around 30 ppm.
Reverse osmosis water will test at 6.0–6.5 pH and show a reading of 20 ppm or less.
If the EC-related problem is not fixed, eventually, the plant will suffer and die.
A digital meter reading of E.C., TDS, and PPM is necessary.
The Role of PPM, TDS, and E.C. in Cannabis Cultivation
During its life, a cannabis plant depends on a specific set of parameters, including the correct water source, nutrient solution strength, and pH levels. The easiest way to think about it is that E.C. and PPM are real-time data that allow you to control what goes in and comes out of the growing medium.
What are E.C. and PPM?
E.C. stands for electric conductivity and measures how much a material can conduct electricity. Salts from liquid nutrients cause electrical conductivity levels to increase when mixed with water, so the more nutrients in your water, the higher the E.C. will be.
PPM refers to parts per million and is directly related to your electrical conductivity levels. PPM is a measurement that describes the concentration of your nutrients in water or soil. Now, if E.C. levels reference the potency of the nutrient solution, why do I need to consider PPM?
It may be overwhelming, but the best way to think about the relationship is in the same sense as degrees Celsius and Fahrenheit, or miles per hour (MPH) and kilometers per hour (KPH). So your E.C. levels will be a reflection of the parts per million. Just remember, EC and PPM both measure the same thing. The easiest way to keep things sorted is to have a reference table for all the various measurements printed out on your grow room wall!
What are TDS levels?
TDS refers to the level of total dissolved solids in your nutrient solution. Measuring TDS is done using parts per million. All you need to remember is that E.C. determines how well electricity can pass through, and TDS refers to the dissolved solids in the water. Measure PPM and TDS levels using the following calculations:
E.C x 500 = TDS levels
E.C x 700 = PPM levels
PPM Conversion chart
Visible Signs of E.C., TDS, and PPM Issues on Your Plants
To make this as simple as possible, it’s all about nutrient levels. Low E.C. levels will mean the plants are drinking more nutrients than are available. High E.C. levels can become uncomfortable for plants. It can also lead to nutrient toxicity (nutrient burn), severe stress, and death in the worst-case scenario.
Below are some signs that you may suffer from low E.C-related issues
Plants will begin to suffer nutrient deficiencies within a short time frame.
Leaves will turn yellow with brown tips as the first signs of a nutrient shortage.
The growth rate of the plants will gradually slow down, causing the leaves to wilt.
Plants cannot access the optimal nutrients, resulting in lower yields.
Mild symptoms of Nitrogen toxicity in a marijuana plant.
Below are some signs that you may suffer from high E.C-related issues.
Plants can experience severe tissue death and necrosis due to high E.C. levels.
Leaf coloration can turn pale green, with the outer edges turning brown and lifeless.
The entire leaf tip can turn fully brown and die off in a short amount of time.
Foliage will display chemical burns, turning the tips of the leaves bright yellow.
Over time, the leaves will become wilted, brown, and brittle.
The plant will eventually suffer and die if the E.C. problem is not fixed.
Symptoms of high E.C. problems during the flowering stage.
Measure Often to Avoid Salt Build-up and Nutrient Lockdown
The golden rule to being a great grower is to measure often to prevent salt build-ups, nutrient lockouts, and a world of problems that may arise later. E.C. and PPM issues can be deadly serious, with the ability to wipe out a crop quickly, leaving an uneducated grower very little room to recover!
Leaf chlorosis can be devastating for cannabis plants.
The Source of Water Matters to Cannabis Plants
Hard water contains high levels of minerals like calcium and magnesium, while soft water has fewer minerals and feels gentler on the skin. However, you can use your measuring device or ask your local water provider for details. According to the U.S. Geological Survey (USGS), water is defined as soft when it contains 60 mg/l (60 ppm) or less of specific ions. Conversely, water with more than 120 mg/l (120 ppm) is classified as hard, while values in between these ranges are considered moderately hard.
Before we cover the different available water sources, it is important to know that the information below are approximate figures. You should always check your own measurements.
Soft tap water
Soft water will have a pH level between 6 and 7, and when tested with a TDS pen, the PPM levels will be between 50 and 300 parts per million and an E.C. level of around 0.4.
Hard tap water
The pH level of hard water will be around 8.5 (so using pH down is necessary). Your TDS meter will reveal the PPM levels are between 320 and 420, effectively meaning the E.C. will be significantly higher than a soft water reading of 0.8 EC.
Reverse osmosis water
Reverse osmosis water will test at 6.0–6.5 pH, your TDS meter/pen will show a reading of 20 ppm or less, and the E.C. levels will be zero. It is worth knowing that the downside to filtering water using a R/O filter is the returns of clean filtered water. It’s a slow process that takes time. Unless you are flushing your plants before harvest, giving them R/O water alone is never advised due to the lack of available nutrients, especially secondary nutrients such as Calcium (Ca) and Magnesium (Mg).
Rainwater
Rainwater can be acidic depending on the atmosphere, pollution, and carbon dioxide levels. Its pH can be tested between 5.0 and 5.5, with 0.4 EC, meaning TDS meters should show 500 ppm. Filtered rainwater tests around 30 ppm.
Monitoring Appropriate E.C., TDS, and PPM of Your Runoff Water?
Salts in the nutrients will naturally build up around the roots and the growing medium. However, salt build-ups can have an adverse effect and cause pH levels to change, causing nutrients to become locked out and subsequently unavailable to the plant.
As a result, the imbalance in E.C. and pH will cause a negative ripple effect. My best advice is to check everything using your hand-held digital EC meter and pH pens. Measure often and always be one step ahead when it comes to feeding your cannabis plants the correct way.
Step 1: Water Plants Until Excess Drains
Step 2: Gather and Analyze Run-Off
What Tools Do You Need to Measure E.C. and PPM?
You should buy a TDS pen or digital meter that can read E.C., TDS, and PPM. Some of the pens available online can do all three (including pH), while others are specific to one value.
Example of a pH and EC meter, placed in water.
How to Analyse the Results of Monitoring E.C. and PPM
This simply means you will need to obtain a reading of the nutrient solution before giving it to the plants and then one from the solution runoff afterward. This creates a system that shows, in real time, how many nutrients the plants use.
The outcome of checking your runoff will be one of three: the runoff will be lower than the original E.C. level, the runoff will be the same, meaning everything is just right, or the runoff will reveal a higher E.C. level.
What is the Ideal PPM, E.C., and TDS for Cannabis Plants to Thrive
The Ideal PPM and EC ranges for hydroponics
The Ideal PPM and EC ranges for soil
How to Achieve the Right Levels of PPM, TDS, and E.C.
So, you have done all your testing and are now ready to compare the data!
In the event, the measurements are the same:
This is a good indicator that the plants are eating up the nutrients without being short of food or overfed. As far as E.C. and PPM are concerned, you do not need to change anything at this point.
When the measurements are lower than what went in:
This means you need to gradually increase the strength of the nutrient solution, as the plants use them quickly. Some strains will be different, so be open to the idea that some plants will use more or less than others during the vegetative and flowering stages.
In the event, you see measurements that are much higher than what went in:
Stay calm, but you may have salt buildup. With this level of nutrient concentration, undissolved salts can build up around the roots and the growing medium. I recommend feeding only water with enzymes and testing the runoff. Keep doing this until the runoff E.C. and PPM readings return to their comfort zone.
Case Study Example
I remember visiting a friend who bought a new brand of coco coir, so I advised them to check the runoff from the coco. To our surprise, the runoff tested a staggering 2.8 E.C. We resolved the issue by washing the coco with enzymes and water until the pH levels were between 5.5 and 6.0 and the new E.C. level was between 1.0 and 1.3.
Now let me explain why using this coco coir would be problematic. The substrate was so rich in salt that the seedlings and clones would have struggled to settle and develop roots. Adding any nutrient solution would have caused the E.C. levels inside the growing medium to have skyrocketed. Nutrients would have been locked out, causing a ripple effect and further nutrient deficiency issues. Without soft water or reverse osmosis (due to the E.C. being so low), maintaining a comfortable E.C. level close to 1.2 would be difficult.
Stoneys Pro Tip: A Note on Enzymes Enzymes are a superb addition to any garden from the seedling stage until harvest. They will increase nutrient uptake and availability, accelerate the decomposition of organic matter, break down dissolved salts in coco coir, and keep roots sparkling white in hydro systems. You can always try to combine multiple enzymes at once. I recommend Cannazyme, Sensizyme, Hydrozyme, Powerzyme, and ATAzyme products.
Common Issue: Calibrating Your TDS, PPM, and EC Pen.
The most common problem I encountered when speaking with beginner growers was calibrating their E.C., pH, and TDS meters and pens. Calibration is extremely important; if not correctly done, it will only result in incorrect E.C. and PPM levels. I strongly recommend learning how to properly calibrate your EC meters, PPM meters, pH meters, and TDS pens by following the instruction guide and using calibration fluid. If you need more information, take a look at Bergman’s Growbible below.
Conclusion
The easiest way to digest everything many consider technical is that pH, E.C., PPM, and TDS are all closely related. The two most important things to know are that your plants need optimal pH levels to absorb nutrients, and the potency of your nutrient solution should be in the ideal range.
With the aid of your digital pen or pens, there is no reason why you cannot control the exact amount of nutrients your plants receive. Overfeeding results in high E.C. levels, and the risk-to-reward factor can lead to stunted plants, low yields, and clear stress on the leaves and foliage. Enzymes are my favorite way to control the amount of salts in the growing medium; however, I suggest checking out Robert Bergman’s Grow Bible and seeing what the main man has to say about the matter! Otherwise, good luck learning the language of water and producing some phenomenal flowers.
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