I’m writing this article based on what I know about general plant growth. There may be more specific information about Marijuana growth. So please feel free to add details that I missed or simply don’t know about.

I am a human physiology student. Human phys? Yes, but the course work requires a lot of study in chemistry and plant biology. I have a lot of knowledge in this arena, however, it’s a whole different world to get this knowledge out of my head and applied to my grow. I am only writing this about the concepts of how pH affects the nutrient uptake of your plants.

There are a few basics to understand before I delve into the wonderful world of chemistry.

Hydrogen is the most basic of elements; it is the mother of all elements and the most abundant in the universe. The Hydrogen (H) atom consists of one proton and one electron. When this electron leaves the atom (for varying reasons), the atom becomes an ion with a positive charge (H+). This ion then seeks anything with an opposite or negative (-) charge. Just so happens that soil particles are negatively charged.

Definition of an acid- a substance that can donate a hydrogen ion (H+), to another molecule or ion.

Now for the fun stuff. Soil (or solution) acidity is measured using the pH scale, which runs from 0 (extremely acidic) through 7 (neutral) to 14 (extremely alkaline).

Plants are affected by pH partly because the solubility of certain minerals differs with changes in pH. For example, aluminum (Al, forming a +3 ion) and manganese (Mn) are more soluble and sometimes absorbed by the roots in toxic concentrations. Certain mineral salts essential for plant growth, such as calcium phosphate, become less soluble and less available to plants at higher pH.

Why is this you ask? The optimum range for nutrient uptake as is evidenced in the above photo is a pH ranging from 6-7, because most essential mineral nutrients are available to plants in that range. Check out these next figure to get a visual of what is occurring.

This figure show how soil works with a normal pH range. Opposite charged ions are attracted to each other (- for soil, + for most minerals), thus supplying needed nutrients to the root system. The next figure represents how acidic soil is locked up causing other essential elements to not be available to the root system.

And that is the quick and skinny on how pH affects the availability of nutrient to the plant. I have also included a figure of the periodic table of elements and listed each period (column) as to what type of ion they form for your reference. Where the number is written each element below forms that type of ion. The elements in the middle of the table are known as transition metals, and there are a few exceptions to the ions they form. If you have any questions about a specific element or need something explained a little more clearly or more in depth, let me know. I’ll try to help. Again this article was written to be somewhat easy to understand, however there is so much more to discuss, theorizes, and just plain ponder. Hope this helps everyone. God I love this shit.