Best Practices for Monitoring pH for Cannabis
05 Mar Best Practices for Monitoring pH for Cannabis
Best Practices for Monitoring pH for Cannabis
Editor’s note: Balancing pH is a critical component to ensuring nutrient solubility and uptake for cannabis. As part of the upcoming release of the Fluence Cannabis Cultivation guide (available later this month), we are releasing tips on how to measure and monitor pH to ensure your fertigation strategy is not a limiting factor to your use of high-intensity LED lighting.
The pH scale — which ranges from zero to 14.0 — provides insight into how chemical compounds will interact with one another based on their ionic state. It is good to remember, pH reflects the concentration of hydrogen ions in a solution. More intuitively however, pH from a practical sense can be understood in terms of acids (vinegar, ammoniacal nitrogen) and alkaline bases (baking soda, potassium bicarbonate).
Caption: Nutrient availability increases or decreases in response to pH. A pH level of 5.8 – 6.2 is appropriate for cannabis.
On the pH scale, values less than 7.0 indicate acidity; values greater than 7.0 indicate alkalinity. Deionized water has a neutral pH of 7.0. The pH scale is a logarithmic function, so even small changes in pH values are significant. For example, a pH level of 4.0 is ten times as acidic as a pH level of 5.0. For plants, pH is important because it affects the form of the nutrients in the substrate.
For example, when pH is low, the solubility of some micronutrients like iron and manganese increases, making them more available to plants. This can cause toxicity. However, when pH increases, micronutrients, along with phosphorus, become less soluble and less available to plants.
Regardless of the concentrations of your nutrient solution, unbalanced pH levels can create an antagonistic environment for nutrients and will make them unavailable to your plants. The figure above shows how nutrient availability relates to pH.
Cannabis, like many plants, prefers slightly acidic soil conditions. It tolerates a wide pH range (5.0-7.0) without symptoms of bronzing or interveinal chlorosis (yellowing of top leaves), but pH levels outside of the optimal range of 5.8 – 6.2 will limit growth. To maintain optimal pH levels, cultivators should test pH levels every two days, and adjust the pH as needed.
Testing pH with a Digital Meter
Testing pH is easy. Combination pH/EC meters are relatively inexpensive and require little training to use. They offer a permanent solution to disposable pH test strips and dye kits, which are cumbersome and must be subjectively interpreted by the color of the reactive test material.
- Calibrate the meter: Before testing, meters require calibration against a known standard. In this case, calibrating against purified water has a neutral pH value of 7.0. Make sure the water you are using is deionized. Submerge the probe of the meter into the water and adjust the display to read pH 7.0.
- Test the solution: Submerge the probe into a container of the fertilizer solution or directly into the tank. Read the digital display.
- Test the growing media: The electrochemical environment of the root zone can be different than that of the fertilizer solution. Salt buildup can cause nutrient concentrations at the roots, which causes pH levels to be different from that of the fertilizer. To test the pH at the roots, stay tuned to the Fluence blog, as we will be releasing a best practices guide to testing for electrical conductivity (EC) in the next few weeks.
We hope these tips have been a helpful reminder of how to leverage pH tests in your grow.
For more tips and best practices, keep an eye on the Fluence blog, as well as stay up to date via Instagram, LinkedIn, Facebook and Twitter to gain access to the Fluence Cannabis Cultivation Guide, which will be available later this month.
How and When to Flush Cannabis
When it comes to flushing cannabis – timing is crucial! Flushing cannabis removes leftover nutrient buildup from the roots and soil of your plants giving them a fresh start. Flushing effectively allows your plants to absorb any nutrients that are still in the soil. By flushing your cannabis plants before harvest you can avoid a harsh and unsatisfying end-product.
If cannabis plants are not properly flushed, the minerals and nutrients used during the cultivation process are still present. Flushing removes all nutrients and improves the overall quality of your bud. Flushing cannabis too early and too often will restrict nutrients and restrain the plants from growing and flowering. Flushing too early can also result in yellowing or discolored leaves.
Finding the best time to start flushing will vary based on how close your plants are to harvest and the knowledge and methods used by the grower.
Generally, flushing cannabis normally takes place two weeks before it is harvested. If the plant has an 8-week flowering period, flushing should start 6-weeks after the beginning of the flowering stage when trichomes begin to form a cloudy white color.
How to Flush Cannabis
1. Test the pH level of the water (tap is acceptable) to ensure it’s in the appropriate range for cannabis plants (between 6.0 and 6.8 for soil grown).
2. Water the plants at the time you would normally feed them without giving them any nutrients or supplements. Don’t water your plants more than usual to prevent deficiencies.
3. Repeat 15 minutes later.
4. To make sure the flush was successful, use a TDS reader to measure the total dissolved solids and find out how pure the water runoff is.
It’s ideal that the water draining out of the pots is as close as possible to the TDS (total dissolved solids) reading of the neutral water you’re flushing with.
5. Keep an eye out for signs of too much yellowing. The pre-harvest flush may cause a plant to lose its color quickly. It’s normal to see some yellowing, but it’s critical to harvest before the leaves on the buds have yellowed.
Once all the leaves have turned yellow your plant is at the end of maturity and buds will start to deteriorate.
6. After flushing, your plants will be a lot lighter in color and are ready to be harvested.
Flushing cannabis is used to remove buildup from the roots and soil of a plant not. It’s been recommended to flush at the beginning or the end of a day when plants can be misted (this lowers their transpiration so that they do not over hydrate).
Flushing Cannabis – The 3 Times You Should
1. Pre-harvest flush
2. Sudden change in the nutrient cycle
3. Nutrient Lockout
1. Pre-harvest flush – Flushing is used during this stage to improve the quality and smoothness of cannabis. A flush during pre-harvest will force plants to use up the nutrients stored within themselves while preventing harshness and removing excess chlorophyll.
If the nutrient reserves are not used or broken down they will negatively affect the quality of cannabis buds. This should be done between a week and 10 days before harvest and repeated three days later.
2. Changes in the nutrient cycle – Cannabis has different nutrient requirements depending on what growth stage it’s in. Cleansing cannabis of old nutrients is a good way to reset soil while a plant is transitioning into a new stage of growth.
Think of this as a preventative flush. It’s not required, but by the time a plant reaches the flowering stage, it has sucked all the nutrients from the soil and could benefit from a fresh start.
3. Nutrient Lockout – Growers that understand how to balance nutrients individually don’t have to worry about flushing as much as those who rely on pre-balanced nutes.
Using pre-balanced nutrients may offer immediate results, however, after the first few doses, your plant is likely getting too much of one nutrient and not enough of the others creating a deficiency. A deficiency in plants is not always due to a lack of nutrients but can be because a plant has too much of a nutrient causing its system to become unbalanced.
By overfeeding a plant’s nutrients, it will absorb what is needed while the access sits in the soil. This leads to a build-up of unnecessary nutrients which is known as Nutrient Lockout.
Generally, when dealing with a serious nute imbalance, the cure is to flush the plants and add a fresh, well-balanced, mild dose of nutrients. It’s important to pay attention to the details; don’t just flush cannabis because of minimal changes.
If you notice a drastic change in your plants but there are no other issues (heat, root rot, etc.), flushing may be a good idea to remove excess build-up and help restore the soils pH balance.
CleanLeaf air scrubbers are designed to provide grow rooms, greenhouses, and other growing facilities with the highest standard of air filtration possible! From odors to pollen to mold and mildew, CleanLeaf Air Filtration Systems has the solution to give your plants the air they deserve.
We are backed by over 40+ years of experience in the air filtration industry and it’s our goal to deliver high-quality standards and long-lasting performance. Get started on your free quote today!
Ph to start weed seeds
Our systems have detected unusual traffic activity from your network. Please complete this reCAPTCHA to demonstrate that it’s you making the requests and not a robot. If you are having trouble seeing or completing this challenge, this page may help. If you continue to experience issues, you can contact JSTOR support.
Block Reference: #f2d4df81-9c10-11ec-9a57-6d5a72785174
Date and time: Fri, 04 Mar 2022 23:15:14 GMT