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Cannabis Growth and pH Levels

Written by Anthony DiMeo

The pH level shows the acidity or basicity of a particular aqueous solution and represents the logarithm of the concentration of hydrogen cations in a solution. In relation to cannabis, the pH spectrum levels affect nutrient availability and the overall health and structure of the plant.

 

Where should cannabis soil fall on the pH scale?

The pH scale ranges from 0 to 14, with 7 as the middle value corresponding to a neutral pH. When it comes to determining which end of the pH scale a compound lies there are two extremes: values that are higher than 7.0 are considered alkaline or basic, while those lower than 7.0 are acids. [1] The typical pH range that cannabis was found to thrive was determined typically as anywhere from 4.0 to 7.0. However researchers at North Caroline State University (NCSU) did find that “cannabis is not prone to iron deficiencies when the substrate pH nears 7.0”. [2]

In determining this optimal pH range, the researchers monitored cannabis plants in their vegetative state. Researchers paid close attention to the tell-tale signs of nutrient deficiency such as blackening, bronzing, or yellowing of lower leaves indicating iron and manganese deficiencies, but found that cannabis does not suffer from these issues, but only of stunted growth. This indicated that cannabis can “regulate micronutrient uptake under low substrate pH conditions.”

So because cannabis can tolerate a somewhat flexible “lower-to-mid” pH range it was further determined by NCSU researchers that to optimally grow cannabis, a great  starting pH range for soil is 5.8 – 6.2. [2]

 

Monitoring and adjusting

In order to properly monitor the pH levels of cannabis, cultivators need to test the levels of the soil with a properly-calibrated digital pH meter every few days and make the proper adjustments. Mixing flowable lime or potassium bicarbonate with water into soil will help correcting low pH levels of soil, thanks to their relatively high neutralizing capacity. If plants are suffering from high pH soil levels, it is possible to acidify the soil with treatments of naturally acidic nitrogen-based fertilizers, acidified irrigation water with sulfuric acid or iron drench. The effects of the pH soil correction can be seen in few days from the first application. [2]

Cannabis has demonstrated a knack for tolerating quite a wider spectrum of nutrient intake. By targeting an ideal pH zone of 5.8 – 6.2, cultivators are able to ensure vigorous growth to promote great yields.

 

References:

[1] https://www.khanacademy.org/science/high-school-biology/hs-biology-foundations/hs-ph-acids-and-bases/a/hs-ph-acids-and-bases-review

 

[2] https://www.cannabisbusinesstimes.com/article/new-research-results-optimal-ph-for-cannabis/

 

Image: https://unsplash.com/photos/F-ZXqLioXxg courtesy of Crystalweed Cannabis on Unsplash

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Anthony DiMeo

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