Picking the best growing medium for your hydroponic system

The benefits of cultivating crops hydroponically are extensive, and many of them are due to the use of a growing medium instead of soil.

Soil comes with a set of risks for farmers, ranging from soil-borne diseases to invading weeds.

Using growing mediums instead of soil mitigates these risks.

In this article, you’ll learn how to choose the right medium for you.

Growing medium, or media, are used in hydroponic systems rather than soil. But growing medias aren’t a true substitute for soil.

The mediums are used to support the roots and stems of plants, like soil, but don’t have any of the nutrients that plants need to grow. As a result, a growing medium can’t grow a plant on its own.

Growing mediums are typically porous in order to hold oxygen and nutrient-rich water.

While growing media is similar to soil, nutrient solution is its true substitute. Nutrient solution is water mixed with nutrients to promote healthy growth.

When choosing a medium, you’ll want to keep three acronyms in mind: WHC, AFP, and CEC.

WHC stands for Water Holding Capacity, which indicates how well the media holds water.

Knowing the WHC of your growing medium is important because some hydroponic systems will be more compatible with lower WHCs and others will be more compatible with higher ones.

For example, wick systems benefit from high WHC mediums, like coconut fiber, because it keeps nutrients easily accessible without overwatering.

Conversely, nutrient film technique (NFT) systems benefit from lower WHC mediums, like clay pebbles, because the plant roots are constantly exposed to nutrient solution. As a result, they use a medium for support reasons more than saturation.

AFP means Air Filled Porosity and is the proportion of volume that is filled with air.

A low AFP means the medium can’t provide the plants with oxygen very well, putting them at risk for drowning and rotting.

Finally, CEC, or Cation Exchange Capacity, refers to the medium’s ability to capture positive ions like potassium, calcium, and magnesium.

In hydroponic systems, a low CEC allows you to have better control over the nutrients your plants receive.

Growing mediums with a higher CEC, like coconut fiber, may require specially tailored nutrient solution in order to achieve the right balance.

Four of the most popular growing media for hydroponic systems are rockwool, lightweight expanded clay aggregate, coconut fiber, and perlite.

Read more at Pure Greens (Leah Soto)

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