Best pH Level for Hydroponics


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Hydroponic gardening is an amazing hobby that allows you to grow plants indoors without soil. However, there are a few things you should know before starting out.

One of the biggest challenges of hydroponic gardening is maintaining the correct pH levels. If you’re new to hydroponic gardening, then you might not know where to start.

In this article, I’m going to give you an overview of the different types of pH levels and how to find the perfect ones for your needs.

What is pH Level?

pH stands for Potential of Hydrogen. It’s basically a measure of acidity or alkalinity in water.

The scale goes from 0-14 with 7 being neutral.

The lower the number on the pH scale, the more acidic it is; while higher numbers mean more alkaline (basic).

When growing plants using hydroponics, we need to keep their roots at specific pH levels, so they can absorb nutrients properly.

pH Levels Scale from Acidic to Alkaline

Why is pH Important in Hydroponics?

The pH value affects plant growth by affecting water and nutrient uptake. The water quality is affected by the alkaline or acidic conditions. 

Even if you have good light, temperature, humidity, and air circulation, without pH level control, your plants won’t be healthy. 

Plants need certain amounts of minerals such as calcium, magnesium and potassium. These elements combine together to form compounds that help regulate cell activity. These elements help them produce chlorophyll, which helps photosynthesis take place.

pH levels in soil are naturally controlled as the minerals, water, and nutrients all work together to help plants grow in soil. 

However, hydroponics requires regular monitoring and regulating of the pH levels to create a growing environment for plants to thrive.

An ideal pH level ensures that the soil gets the right amount of nutrients needed for growth. This is important because each type of plant needs a different amount of nutrients. Some nutrients are more affected by the pH than others.

Typical pH Ranges for Crops

Successful hydroponic growing requires a specific pH range for optimum growth.

Most fruits and vegetables require a pH between 5.5 and 6. These are usually your apples, tomatoes, beans, melons, and squash.

Some fruits and vegetables, such as blueberries, require a lower pH between 4.0 to 5.0, that’s more acidic.

It is important to use separate water tanks and nutrient reservoirs when growing plants with similar pH requirements.

Not all crops need a narrow pH range, some hydroponic crops can be grown in a wide range of pH levels.

Here’s a handy pH level chart for many fruits and vegetables: 

PlantpH Level
Basil5.5-6.5
Bean (Common)6.0-6.0
Bean (Broad)6.0-6.5
Bell Peppers6.0-6.7
Broccoli6.0-6.5
Brussel Sprouts6.5-7.5
Cabbage6.5-7.0
Cauliflower6.0-7.0
Celery6.3-6.7
Chives6.0-6.5
Cucumber5.8-6.0
Eggplant5.5-6.5
Kale6.0-7.0
Lavender6.4-6.8
Lemon Balm5.5-6.5
Lettuce5.5-6.5
Melon5.5-6.0
Mint5.5-6.0
Onions6.0-7.0
Pak Choi7.0
Parsley5.5-6.0
Peas6.0-7.0
Peas (Sugar)6.0-6.8
Peppers (Bell)6.0-6.5
Peppers (Hot)6.0-6.5
Pumpkin5.5-6.5
Sage5.5-6.5
Spinach5.5-6.6
Squash5.0-6.5
Strawberries5.5-6.5
Swiss Chard6.0-6.5
Thyme5.5-7.0
Tomato5.5-6.5
Watercress6.5-6.8
Watermelon5.8
Zucchini6.0

Typical pH Ranges for Nutrient Systems

Nutrients play an essential role in helping plants grow. They also affect the taste of food.

Hydroponic products that help add nutrients to hydroponic systems can affect the pH levels. Most products will start at pH levels between 5.5 and 6.0. 

For example, ammonium nitrate causes a more acidic effect than nitrate and can result in a drop in pH. Nitrates cause a rise in pH and calcium salts cause a rise in pH.

Some nutrients require specific pH levels for plants to successfully take the nutrients, but too low or too high pH levels can lead to nutrient deficiencies or toxicities.

Too low pH levels may be caused by too little rainfall or irrigation, too much fertilizer or other chemicals, or too many acidic gases such as sulfur dioxide.

When pH levels are lower than 5.0, it could lead to plants suffering calcium and magnesium deficiency. At those levels, it could also lead to iron and copper toxicity.  

Too high pH levels may be caused, for example, by too much rain or irrigation, too much fertilization, or too many alkaline gases such as carbon dioxide. Above 6.0-6.5, it could lead to an iron deficiency. 

Causes for pH Level Changes in Hydroponics

Changes in pH levels in hydroponic systems can come from several sources, including:

  • Fertilizer and Nutrient Solution Changes – Fertilizers contain nitrogen, phosphorus and potassium. When these three nutrients run out, there isn’t enough available for new leaves to develop. That means less leaf area and fewer fruit buds. It’s important to keep an eye on your nutrient solution and pH levels to ensure that the reservoir is full.
  • Water Quality Issues – The main reason why pH drops occur is due to poor water quality. Poor water quality includes having hard water, chlorine, ammonia, phosphates, sulfate, etc. Hard water contains minerals like calcium and magnesium which make them harder to dissolve. Chlorine kills bacteria and algae causing oxygen depletion. Phosphates kill beneficial microorganisms while sulfate makes soil acidity. Ammonia increases plant growth rate. All of these factors contribute to lowering the pH levels.
  • Overfilling Containers – Overfilling containers leads to higher concentrations of CO2 gas inside the container. This results in increased photosynthesis rates leading to faster vegetative growth. However, if overfilled containers have no ventilation holes then excess CO2 builds up resulting in lowered pH levels.
  • Organic Matter – Organic matter has a natural buffering capacity. If organic matter gets into the system, it helps maintain proper pH levels. But algae and bacteria are exceptions. Algae can cause higher pH levels in the morning and lower levels at night. Bacteria can cause a drop in pH levels by releasing acids.
  • Non-Organic Matter – Inorganic materials do not buffer well, so they tend to raise pH levels. For instance, sand tends to increase pH levels because it doesn’t absorb any acids. 
  • Temperature Fluctuations – Temperature fluctuation affects the amount of dissolved solids present in the nutrient solution. As the temperature rises, more soluble compounds precipitate out of the solution. In turn, this lowers the total concentration of dissolved ions in solution. For instance, when temperatures increase above 50°C, some common mineral solutions become supersaturated with respect to their solid phases, and pH levels change.

How to Manage pH Levels in Hydroponics

Maintaining pH levels within optimal ranges will help you achieve maximum crop yields. Here are some tips to follow:

Monitoring pH Levels

You should monitor pH levels regularly throughout the growing season. Use test kits designed specifically for use in hydroponic applications.

These tests include digital pH meters, strips, and colorimeters. They’re easy to read and inexpensive. Make sure to check all parts of the tank before using the meter. Also be careful about how much fertilizer or other chemicals you add to the tank as this may affect the readings.

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Adjusting pH Levels

Once you’ve determined what level of pH you want, adjust accordingly. There are many ways to accomplish this, including adding buffers, adjusting the ratio of fertilizers, changing the type of fertilizer being added, increasing aeration, and/or reducing evaporation. 

If you want automatic adjustments, you can get a pH controller that automatically adjusts your pH based on the current conditions. These controllers also allow you to set specific target values. You’ll need an external power source to run the unit. Some units require manual calibration every few days. Others work without recalibration.

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Last update on 2021-10-16 / Affiliate links / Images from Amazon Product Advertising API

Adding Buffer Solutions

A good way to control pH levels is through  the addition of buffers. Buffers are substances that neutralize acids and alkalines. Adding buffers to your tanks will keep pH levels from dropping too low during periods of high activity.

It’s important to note that buffers don’t always prevent pH fluctuations. So, even though they might seem effective, there could still be problems.

Increasing Aeration Rates

If you notice that pH levels are getting too low, try raising the rate of air circulation around the plants. You’ll need to experiment to find the right balance between aerating enough but not too much.

Too little airflow means less oxygen reaches the roots, which causes them to grow slowly. On the other hand, too much airflow increases water loss and reduces plant health.

Hydroponic pH Levels Final Thoughts

It’s best to maintain ideal pH levels by monitoring these factors and levels onstinuously. If you do experience any issues, make changes immediately so you won’t have to deal with them later.