Effects of pH and Temperature on Organic Nutrients

There are several essential factors to consider for getting the best quality and yield from your growing operation. A critical contributor to the uptake of plant nutrients is monitoring and controlling the pH of your water.

Acid is the ingredient that makes soda pop taste sour, and the base is the ingredient that makes soap feel slick. Typically, we don’t want to use taste or feel to know the acid and base content. So, what is pH exactly, why is it so important, and how do we measure it?

What is pH?

pH is a measurement of how many hydrogen ions are floating around freely in your water. Distilled water is neutral (pH=7) because all the hydrogens are securely bound to oxygen.

Adding hydrogen ions from lemons or vinegar can change the pH of water, lowering the pH to 3-4 units. Low pH is called acidic. Adding hydroxy ions from soap or baking soda can raise the pH by 8-10 units, and high pH is called basic.

We can measure pH in many ways. Measuring pH is the way we determine how much free hydrogen ions exist in the water. We can use a pH probe with a digital read-out or pH paper that changes color depending on the pH range, or we can even use chopped-up red cabbage!

How does temperature affect pH?

Measured pH can change by 0.2 degrees with only a change in temperature of 10 degrees. On a hot day of 80 degrees, the pH will be 0.8 pH units different than on a cold day of 40 degrees.

If we measure our water mixture on a warm day, it will differ by almost 1 unit compared to on a cold day without any changes to the mixture. It could be 6.0 units on a cold day and 5.0 units the next day without adding pH up or pH down ingredients.

How can we maintain pH in our water systems with all these factors? The primary way living systems support a small pH window is to use a buffering system. 

What is a buffering system, and why is pH control essential to living things?

Buffering systems resist change to pH by capturing hydrogen ions or releasing hydroxy ions back into the water. Controlling the hydrogen in our solution keeps the pH steady even if we were to add strong acids or bases. Your blood is a buffering system that controls pH between 7.35 and 7.45 units in your body.

Ranges outside of this would be damaging to humans. The ocean is a sizable buffering system maintaining its pH range between 7.5 and 8.5 units. The viability of fish and plant life will be in question if the pH drifts outside this range.

Cannabis plants also need pH control to get the necessary nutrients to thrive. pH outside the 5.5 - 6.1 scope for a hydroponic plant grown will tie up the nutrients by changing them to a form that the plant cannot readily absorb.

Essential growth nutrients like Gaia Green product lines can be used in coordination with a buffering system to maintain consistent daily plant nutrients.

Why can’t plants feed on nutrients at the wrong pH?

Plant macro-nutrients such as nitrogen, phosphorous, and potassium (NPK) can be very sensitive to changes in pH. Nitrogen-containing compounds readily act as bases in water.

Some more minor examples of ionic nitrogen are compounds like ammonium nitrate, and many organic nutrients are more complex molecules such as phenylalanine. If these nitrogen nutrients are in an acidic solution, they can be neutralized or converted to a solid salt which can clog the roots and prevent plant nutrient uptake.

The same situation holds for phosphorus, potassium, and micro-nutrients. There are wide varieties of NPK ratios on the market for soil amendment and hydroponic plant nutrients.

One of the more even ratios for an all-purpose organic nutrient is a product known as Gaia Green All-Purpose, which has a 4:4:4 standard ratio.

Other ratios are more specific to outcomes like flowering and blooming. For blooming growth cycles, using 2:8:5 ratios like Gaia Green Power Bloom are more suited.

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