Why is pH Important for Growing?

By Millie Traynor

As a hydroponic grower, you are always trying to keep the conditions perfect in your grow tent.

And one condition that needs to be measured is pH. Unfortunately, pH levels are often overlooked or badly managed by hydroponic growers, which can have serious consequences for the plants. On the plus side, pH levels are relatively easy to test and control. You just need to know how. 

In this article, we will look at exactly what pH levels are and why they’re important for hydroponic growing. Then, we’ll explain how to measure and control it. 


What is pH?

Before you start measuring pH, it’s a good idea to understand some of the basic science behind it. It stands for ‘power of hydrogen’. It’s basically a numerical value of the hydrogen ions in a nutrient or water solution. This determines whether a solution is acidic or alkaline. Here’s how the scale works - 

 pH Level Infographic

The more acidic a solution, the more hydrogen ions it has. The more alkaline a solution, the fewer hydrogen ions it has. 


How do pH Levels Apply to Hydroponics?

Now that you understand what pH is, you need to know how it relates to hydroponics. 

The pH level of a solution has a huge effect on crop growth. This is because it affects how many nutrients are available to the plants. Finding the perfect level of acidity is the key to unlocking the maximum number of nutrients. If the pH level is not in a certain range, it can cause nutritional deficiencies or toxicities. 

To sum up - you need to find the right pH level to unlock the maximum number of nutrients.


What is the Typical pH Range for Crops?

The pH level you will need depends on what you’re growing. Typically, the optimal pH range is between 5.5 and 6. This is true for most fruits and vegetables (melons, apples, tomatoes, etc). However, some need a slightly different pH level. For example, blueberries need a pH range of between 4 and 5; and kale, onions, and peas need a pH range of between 6 and 7. The first step is to find out what pH level your plants need. 


What is the Typical pH Range for hydroponic nutrients?

In most cases, a base nutrients product will have a pH level of between 5.5 and 6 (the optimal level for most crops). However, some solutions differ from this. For example, ammonium nitrate can cause a drop in pH, and calcium salts can cause a rise in pH. 

You need to know your nutrients,  and what pH levels they need for maximum growth. Only then can you check and control the pH level. 


How do you test the pH level? 

You need to check the pH of your solution to make sure it’s in the proper range. At Ashton Hydroponics, we have a whole range of pH management products (like pH up and down) that can help you with this task. One of the most common tools is a digital pH meter, which simply tells you the pH level in your solution. 

How to test the pH level is also determined by the type of system you are using. If you are using a media-based system, you need to test the water that drains from the grow bed. If you use a recirculating system, you need to test the water in the supply reservoir. 

You need to test the pH level regularly because there are several factors that can cause it to change, which could lead to a drop in nutrient uptake. If you have recently changed the nutrient levels or changed the nutrient additives in your growing systems, you should test the pH level every day. 


Why does the pH level change? 

There are several factors that can cause a change in the pH level. Here are the main ones to look out for: 

  • When the amount of nutrient solution drops below one gallon, the solution becomes more concentrated as the plants absorb the nutrients. This can make the pH levels change dramatically, so it’s important to monitor the level of nutrient solution in your reservoir. 
  • Organic matter can cause a change in pH levels. Algae and bacteria are the main types of organic matter that affect pH levels. 
  • Inorganic matter can cause a change in pH levels. For example, gravel can cause a rise in pH levels in a media-based system. 

How do you control the pH level? 

The first (and most important) step is testing. You need to know how to test the pH level before you change it. Scroll back up to find out how to test your pH level. 

There are multiple ways to control the pH level in your system. Here are some of the main ones you can find in a grow shop. : 

pH up - Raises the pH level of the solution. Comes in a dry or liquid form. 

pH down - Lowers the pH level of the solution. Comes in a dry or liquid form. 

Automatic pH controller - Automatically controls the pH level of the solution. More expensive and works best for recirculating systems. 

Vinegar or citric acid - Cheapest option. Only suitable for small systems and only provides short-term results. 


Take Buffering Capacity Into Consideration

Another consideration is the buffering capacity. This is the nutrient’s ability to resist a change in pH. Most of the time, this won’t be a problem for hydroponic growers. However, if your source is hard water (which it commonly is) it could have an effect. This is because hard water contains lots of carbonates and these are good at buffering water at a high pH. So, if you add pH down and it doesn’t help, it’s probably because the carbonates are increasing the buffering capacity. To combat this, check carbonate levels in the water regularly. 

If you need any more information about the importance of pH in hydroponics, don’t hesitate to get in touch

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