Quick pH Discussion

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What is pH and why is it important for plant growth? (video)

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Potential hydrogen (pH) is a measure of how acidic/basic water is. The range goes from 0 – 14, with 7 being neutral. A pH of less than 7 indicates acidity, whereas a pH of greater than 7 indicates a base. Every number on the pH scale represents an increase or decrease in concentration to a power of ten. For example, a solution with a pH of 6 is ten times more acidic than a solution with a pH of 7, and a pH of 5 is one hundred times more acidic than a pH of 7.

Why is pH important for plant growth?

The pH of water determines the solubility, the availability of nutrients (phosphorus, nitrogen, and carbon) and heavy metals (lead, copper, cadmium, etc.). This is important for plant growth because if the pH is either too high or too low some plant nutrients convert to forms that are more difficult to absorb resulting in nutrient deficiencies and plant stress. Below is a picture briefly explaining the soil reactions at different pH levels:


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Optimal pH for cannabis from The Weed Blog:

For several reasons the pH has a profound effect on the cannabis plants. Various plants live under different pH levels, they have adapted to this. In hydroponic solutions marijuana grows with a low pH of 5.5. Marijuana grows best in water or soil with a pH level between 6.0-6.5 (slightly acidic). Good garden soils consist of this pH level. In this range the plants nutrients are water soluble. This means that the nutrients are available to the marijuana plants. When the pH level is outside of this range, the nutrients become less available because the nutrients won’t dissolve as well. –The Weed Blog

How do you adjust the pH level?

Using pH test papers or pH meters, measure the pH levels of the water that will be used to feed the plants. From there you can determine if you want to lower or raise the pH level. For lowering the pH you can use elemental sulfur, aluminum sulfate, acid sphagnum peat, and some fertilizers. If you need to raise it then you can use lime (calcium carbonate). The key is to use a properly calibrated pH meter that will get you a detailed and correct reading on the pH level.

Having a general understanding of pH and how it can effect your garden is important for a grower. A substantial amount of time and money goes into nutrients and soil health, which would all be a waste if the pH level is off in the garden. A greenhouse will give you the proper environment to grow , but if the plants are being starved of their nutrients they will never grow to their greatest potential.

Do you have any experience with this topic? What do you use to control your pH? Please leave your thoughts in the comment section below.


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