Understanding pH

We published the following series of blogs on pH with the intention to cover every aspect that affects cultivators. We started with the basics in Part 1, followed by a slightly more specialized set of facts in Part 2, then wrapped the series up with practical applications in the third and final blog, “pH in Practice.”

UNDERSTANDING pH: MORE THAN YOU WANTED TO KNOW (PART 1)

• The chemistry of pH, acids, and bases

• Practical implications for cultivation

Introduction

We all accept the importance of pH in hydroponics as it relates to fertilizer and substrate management, but often ignore the underlying science. Given this fundamental importance of acids and bases in chemistry and their influence on a range of chemical reactions involved in hydroponics, I think a deeper understanding is warranted. This article aims to do this by starting with the chemistry of pH, acids, and bases and building up to the practical implications for cultivation. In part 2 we’ll explore more of the practical implications of this science, and best practices around pH management in hydroponics.

Hydrogen, Hydroxide, and Hydronium Ions

Fundamentally, acids and bases are two types of substances defined by their ability to accept or donate protons (H+ ions). Understanding the dynamics of hydrogen (H) atoms is critical to understanding the nature of acids and bases.

• A hydrogen atom (consisting of one proton and one electron) can transform into a positively charged hydrogen ion (H+) (a lone proton) in a water-based solution as it loses its electron. However, in such solutions...

Read the rest of this article at https://www.frontrowag.com/blogs/info/understanding-ph-more-than-you-wanted-to-know-part-1

Understanding pH: MORE THAN YOU WANTED TO KNOW (PART 2)

• How nutrient absorption affects rootzone pH

• When to use acids or bases

• Commonly used acids and bases in hydroponics

• Considerations on pH management

pH CHANGES IN THE SUBSTRATE

As we’ve established, nutrients are generally best absorbed between 5.8 - 6.2 pH, but it’s not always quite as simple as just setting the pH of the feed solution and forgetting it. Several factors can influence the pH in the root zone, especially the interaction between the plant roots and the fertilizer solution.

The nutrients in hydroponic fertilizer solutions exist as positively charged ions (cations) and negatively charged ions (anions). To effectively absorb these ions, the plant roots needs to maintain electrical balance. When plants take up cations (with their positive charge) they release an equivalent number of H+ ions (also positive charge) and when they take up anions (negative charge), they release an equivalent number of hydroxide (OH-) so as to maintain electrical balance. The preferential uptake of different nutrient ions can cause the pH of the substrate to “drift” over time.

Common cations in hydroponic fertilizer solutions include potassium...

Read the rest of this article at https://www.frontrowag.com/blogs/info/ph-part-2

pH IN PRACTICE

• Adjusting pH levels,

• Choosing from common bases and acids for pH adjustment,

• Understanding the sequence of pH adjusters for fertigation systems

• The importance of calibration and accurate pH measurement.

Introduction

In Controlled Environment Agriculture (CEA), managing the pH of nutrient solutions is a fundamental aspect of ensuring optimal plant health and growth. This article focuses on the importance of adjusting pH levels in facilities using low EC water sources like Reverse Osmosis (RO) or rain catchment systems, as well as those with higher EC city or well water. The article discusses choosing and using common bases and acids for pH adjustment, including Potassium Hydroxide, Potassium Carbonate, Phosphoric Acid, and Sulfuric Acid. It also covers the sequence of adding pH adjusters in fertigation systems and the importance of accurate pH measurement and calibration.

RAISING pH

This is generally required for facilities using very low EC water from Reverse Osmosis (RO) or rain catchment, due to low levels of preexisting alkalinity. The low buffering capacity that results from lack of alkalinity means that these water sources will be very sensitive to the pH effects from fertilizer and pH adjusters. These facilities will need to use one of the common bases to raise the pH of their fertilizer solution:

Potassium hydroxide (KOH) - This is a strong base that exerts large and immediate changes to solution pH. While this can be desirable in some situations, it’s very important to dilute it, then add it very gradually to not cause unfavorable...

Read the rest of this article at https://www.frontrowag.com/blogs/info/ph-in-practice