Cannabis nutrition can be a difficult subject and can seem impossible to understand. This article is aimed to explain how to solve problems with Cannabis nutrition, and to explain several principles behind optimizing your nutrition. The following sections explain the function and importance of E.C. and pH in Cannabis cultivation as well as preventing and solving problems in these areas.
Cannabis nutrition problems can occur due to abnormal amount of total dissolved solids (TDS), which can be measured through electric conductivity, or E.C.. Many growers use an E.C. meter to check the level of dissolved salts in the water, this number is usually converted to a value in P.P.M. (parts per million). E.C. meters are easy to use, after a straightforward calibration step all you have to do is put the side with the electrode in the solution for a few seconds and a value will appear on the screen. If your E.C. meter gives values in P.P.M., make sure to check the conversion factor it uses, this information should be provided by the meter’s manufacturer.
E.C. values also depend on the temperature at which they are taken and change around 2,5% per degree Celcius. Most values provided by E.C. meter manufacturers are based on measurements at 25 ºC. While it is always good to set yourself the goal of measuring E.C. accurately, for Cannabis nutrition it is probably more importantto know the direction in which it changes. The p.p.m. value of hydroponic Cannabis nutrition can range between 200 and 2000 p.p.m. between different grows. When growing Cannabis it is therefore more important to know whether your E.C. or p.p.m. is going up or down, than how to compare solutions to those in other grows. In short, E.C. values dropping means that nutrients are being used faster than water, and when E.C. values rise the opposite is true.
The reason E.C. levels are vital to the development and growth of a Cannabis plant is because they allow you to closely monitor and regulate the amount of nutrients your plant consumes. A young Cannabis plant has not yet adjusted to high levels of salts in nutrient solutions and should therefore be fed with a “soft”, diluted solution. As plants begin to grow and enter the flowering stage, they will be more adapted to a higher concentration of nutrients and will be able to handle a stronger nutrient solution. Nutrition for Marijuana plants is usually sold with a feeding chart that indicates how much nutrients to use at what stage. While the exact numbers may be slightly different per setup and per grow, these charts provide a good guideline. It is good practice to start by using half the amount of nutrients that the manufacturer suggests to avoid overfeeding. You can fine tune your Cannabis nutrition later by watching how your Cannabis plant reacts to this diluted feed.
E.C. meter. This handheld E.C. meter is very easy to use and displays the measurement in parts per million (which is the same as mg/L). The PPM value of this solution is 840.
Problems With E.C.
Growers should check the E.C. value of every Cannabis nutrition solution they prepare before application. Among other differences between growing Cannabis organically or hydroponically, nutrition for organic grows can have a higher E.C. value.
Measuring The Runoff
When a plant cannot digest the amount of dissolved nutrients within the medium, Cannabis nutrition problems can occur quickly due to the buildup of salts. This buildup can cause a lot of stress for a Cannabis plant and will slow its metabolism down until the excess salts are flushed out of the medium. Measuring the runoff from your Cannabis plant, especially in hydroponics setups, will tell you whether the nutrients you are providing are actually taken up. A healthy Cannabis plant will use up a substantial amount of nutrients, but will not be lacking any of them to begin with. If the E.C. value of your runoff is much lower than your nutrient solution, it is very likely that you are not feeding your Cannabis plant enough. Whereas if the E.C. value of your runoff is much higher than that of your nutrient solution, it is likely that you are overfeeding and salts have built up in your medium.
A clear sign of salt buildup is when the bases of pots are stained with a white salt residue where they were in contact with the nutrient solution after a crop.
pH, short for potential hydrogen, is a measure of the concentration of free hydrogen ions in a solution, but in practice describes how acidic or alkaline a solution is. The pH scale goes from 0 to 14: a pH value of 7 is neutral, anything below 7 is acidic and everything above 7 alkaline. Everything on the planet must adapt to certain levels of acid and alkaline both inside and outside of the body. pH affects the solubility of nutrients and the functionality of enzymes, which means that swings in pH can have drastic effects on the health of any organism. If regulation of pH is not accurate in humans, this will cause dramatic problems with oxygen regulation and metabolism in general. As this is true for all organisms, it makes sense that Cannabis plants need a specific pH range in order to be healthy and avoid Cannabis nutrition problems.
Availability of nutrients at different pHs. If the pH of the medium is too high or too low a Cannabis plant will not absorb certain nutrients, this is called “nutrient lock-out”.
Problems With pH
Similar to when a Cannabis plant experiences a nutrient lock out due to high E.C. levels, a big enough shift in pH can have serious consequences. If you have made your nutrient solution and cannot find the sweet spot between 5.2-5.8 then the plants will adapt to deal with this. Large changes in pH will slow down the entire metabolism of a Cannabis plant and will negatively affect the growth rate, nutrient uptake and immune system. The amount of nutrients that is required during different stages of growth changes, so it is important to keep an eye on pH values after preparing your nutrient solutions and avoid large differences between feedings. It is also important to check whether the pH of your runoff is within a healthy range, especially when growing in a hydroponic setup. An extremely high or low pH value in the runoff can imply countless different problems, however the majority of these problems can be solved by simply flushing your medium.
This easy to use pH meter measures a solution’s pH through an electrode at the tip that is submerged in the solution. This solution is acidic, with a pH of 4,96.
Water Is Different Everywhere
Depending on your region, tap water can have a pH value of anywhere between 6 and 8,5. Amsterdam tap water has a pH value of around 8.0 for example. It is important to realize that even if Cannabis nutrition packaging states a pH value after mixing, this is usually based on pH adjusted water. In general, you want to check the pH before you give any solution to your Cannabis plant, including water.
Preventing Cannabis Nutrition Problems With E.C. And pH
The ability of a Cannabis plant to absorb and use nutrients is largely determined by the pH, as well as the amounts of nutrients presented to the plant at a time. Before growing Cannabis in a new medium and having to repair it from the beginning, it is worthwhile to invest time in learning how this medium usually behaves. In soil grows this is usually easier as the complex composition helps keep pH in a stable range, this is known as buffering. Hydro media like coco, rockwool and mapito behave differently than soil when it comes to pH because they do not buffer as well as soil. While this has many other advantages, it does mean that your Cannabis nutrition has to be correct from the beginning. Many hydro media need to be flushed several times before their pH remains stable and skipping these steps will cause wild pH fluctuations. After this it is important to keep a close eye on your pH and E.C. levels throughout the grow, as it will allow you to adjust these ranges before any serious problems occur. You should check E.C. and pH values once or twice per week, but measuring more often will only help and ideally you would do this twice per day. The recent introduction of pH Perfect, a new line of Cannabis nutrition by Advanced Nutrients that contains a buffering solution can be of great help to keep pH in a stable range.
Buffered Cannabis Nutrition. pH perfect is a nutrient line by Advanced Nutrients that contains a buffering solution that is designed to stabilize your pH.
Growing Cannabis In Soil
The only way to combat the issues of nutrient lock outs due to salt buildup from nutrients is to flush your medium as best you can. If you are growing Cannabis organically you have an advantage as the organic medium will naturally buffer the nutrients. Growing in soil is preferred by many medicinal Cannabis growers for this built in reliability. However, if it is evident the imbalance is too big to buffer, then you must wash out all of the salts building up in the medium and around the roots. This should be done with water and can be assisted with products like Grotek Final Flush, a solution that is specifically designed for flushing media. The enzymes will help break down salt deposits in order to be sure all salts are removed from the medium.
Salt Flushing Solution. Products like Grotek Final Flush are designed to help flush any salt buildup from Cannabis nutrition out of a medium. They are often used for the flushing phase of a grow, but can also be used to prepare hydroponic media for re-use.
Growing Cannabis In A Hydroponic Medium
In a hydroponic setup a Cannabis plant is grown in liquid and receives the nutrient mix continuously. If you discover Cannabis nutrition problems within your system, it is necessary to remove the old nutrient solution and replace it with a new solution with acceptable E.C. values and a well adjusted pH. The advised E.C. value ranges are usually provided with Cannabis nutrition products. The chance of pH and E.C. problems are far more imminent when growing Cannabis hydroponically than they are when growing in soil. A large part of this is caused by the temperature dependant nature of pH and E.C., a few degrees warmer or colder can cause huge shifts in both. Preparing nutrient solutions is much less forgiving because there are no other components that can help buffer pH and less microorganisms to aid nutrient absorption. A poorly mixed nutrient solution can ruin an entire crop. Another reason is that the water in a hydroponic setup needs to be oxygenated, but changes in dissolved oxygen can also cause huge swings in pH. An unattended broken pump can therefore also have a much larger impact than just stunting root development.
Adjusting Your Cannabis Nutrition Solution
Changing the pH of nutrient solutions is very simple regardless of whether you are growing Cannabis in soil or hydro. It does however require something to measure the pH value of your solution with. The cheap option for this is the litmus test, which is a disposable strip of paper that changes colour depending on the pH of the solution it is submerged in. A slightly more expensive option, but one that we recommend, is buying a pH meter. These are used the same way as an E.C. meter and can be reused for years. You can measure the pH of a solution with a digital pH meter by simply hanging the side with the electrode in the solution for a few seconds, after this the screen should read out a pH value. After you know what the pH of your solution is, you can easily adjust this by adding solutions specifically designed for adjusting pH. These products, usually named “pH up” or “pH down”, are readily available in most garden centers, grow shops and stores that sell supplies for swimming pools. If the pH of your nutrient solution is too high when you measure it for the first time, simply add a few drops of pH down, mix well and measure again. By repeating this process you can easily adjust the pH value of your solution without increasing the E.C. value. The E.C. value of a Cannabis nutrition solution can be adjusted by simply diluting with water or increased by preparing your solution in less water. It is important to note that there will always be a little variation between feedings when adjusting pH. This is because most digital pH meters work with two decimals, and that it is virtually impossible to correct the pH of a relatively small volume to exactly the same value every time.
Adjusting Your Soil?
For soil grows, it is very important to make sure that not only your Cannabis nutrition, but also your soil is in the right pH range from the beginning as this is less flexible as the grow progresses. A Cannabis plant will usually perform best if the soil pH is slightly acidic with a value of around 6. A very practical tool for keeping an eye on your soil pH is a soil pH meter, these are different than regular pH meters as they do not require a liquid. They are also very easy to use, all you have to do is stick the meter in the soil and leave it there for 60 seconds. The downside of soil pH meters is that they are often less accurate than pH meters that measure liquids. Avoid leaving a soil pH meter in soil for long periods of time to avoid damage. For more accurate measurements you can mix soil with pH balanced, demineralized water and measure the pH of the solution using a meter designed for liquids. Soil pH measurements allow you to check whether the pH value on bags of soil is correct and also to see what effect watering and feeding has on your soil pH. If soil pH changes too much over time, it is a good idea to adjust the pH of your nutrient solutions to compensate. If the soil pH decreases to around 5 and your nutrient solution is at 6 for instance, you could adjust the nutrient solution pH to 6,2 to make sure soil pH does not drop more.
Final Thoughts On pH and E.C.
Knowing your pH and E.C. values helps a lot when growing Cannabis as this can help prevent problems and increase yields. Growers should become comfortable with pH and E.C. measurements, even though this may seem intimidating at first. And you should definitely be able to measure and adjust both before growing Cannabis in a hydroponic setup! For more in-depth information about the role of different nutrients, also read our article on Cannabis nutrition and deficiencies!