What is pH?

Soil and nutrient pH are very important factors in greenhouse crop cultivation. But what exactly is pH?

This article might be a little science-heavy for some, but we will try to boil it down for you as best as we can!

The pH value of a solution is a key chemical characteristic and can largely affect plant health. For plants, the pH of the soil can drastically alter their productivity because hydrogen ions play an important role in photosynthesis. pH adjusters are often used to treat soil and ensure plants stay healthy and continue to metabolize nutrients and create energy. 

Most plants have some level of tolerance to small shifts in pH balance. However, as the plant becomes more stressed by much higher/lower levels outside of its tolerance, its health will greatly decline and it will likely die if strained conditions persist, or if it is immediately exposed to a toxic level.

pH in a Nutshell

  • pH value measures the concentration of hydrogen ions in a solution and rates that concentration on a scale from zero (acidic) to 14 (basic/alkaline)
    • Acidic Substances: vinegar, lemon juice
    • Alkaline/Basic Substances: lye, milk of magnesia, and ammonia
    • Pure water is neutral with a pH of 7
  • Each whole pH value below 7 is ten times more acidic than the next higher value
  • Substances called buffers may be applied to solutions to adjust the pH
  • Mixing acidic solutions with alkaline solutions can cancel out the two extreme chemical properties and create a neutral solution
  • When mixed with water, a chemical mixture can become either acidic or basic
  • The concentration of free hydrogen ions is what is specifically measured by the pH scale:
    • H+ and OH- ions are present in any solution (liquid) at all times
    • If base ( OH-) is added to water, the H+ concentration decreases- this makes a solution more basic
    • If an acid (H+) is added to the water, the OH- ion concentration decreases- this makes a solution more acidic

The pH Scale

An acid is a molecule that donates hydrogen ions. Acids increase the concentration of hydrogen ions in a solution.

A base is a molecule that donates hydroxide ions or binds excess hydrogen ions. Bases decrease the concentration of hydrogen ions in a solution.

Buffers are substances that prevent a change in pH. They accomplish this by absorbing or releasing hydrogen or hydroxide ions.

pH scale

pH Scale by Piercetheorganist

Measuring pH

Litmus paper (pH paper) is a type of paper treated with a dye that changes its color as the pH of the environment changes so it can be used as a pH indicator. Electronic pH meters can be used to make more precise measurements of pH, and special meters can be used for soil to measure pH and moisture levels.

Soil pH & Moisture Meter

soil pH and moisture meter

  • Professional pH and moisture meter
  • 12 in probe
  • Can measure pH and moisture at depths up to 12 in
  • No batteries are required
  • Meter comes with a cleaning pad.

Digital Waterproof pH Meter

digital pH meter

  • Measures pH and temperature
  • pH buffer 4 solution is in a sponge embedded in a clear cap
  • Measurement range: 0-14 pH with waterproof housing
  • Digital automatic calibration (one point), with digital fine-tuning
  •  Auto-off, data-hold functions, and low battery indicator

Adjusting pH

If you need to correct pH, you will need a product like pH Up or pH Down. These solutions allow you to quickly adjust the pH of your nutrient solutions without adding anything that will alter the nutrient formulation. pH balancing your nutrient solutions is a fast and easy way to avoid more complex issues and makes nutrients more available to plants.

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