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 media instead of soil mitigates these risks.
In this article, you’ll learn how to choose the right medium for you.
Growing media are used in hydroponic systems rather than soil. Growing media are typically porous in order to hold oxygen and nutrient-rich water. While growing media is similar to soil, the nutrient solution is its true partner.
The 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 the nutrient solution. As a result, they use a medium for support reasons more than saturation.
AFP means Air Filled Porosity and refers to the airflow of the medium.
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 how many minerals are in the medium.
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 a 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.
Rockwool
Rockwool, also known as stonewool, is a porous material made of spun basalt rock fibers.
This growing medium is extremely popular due to it’s high WHC and low CEC. It absorbs easily and drains well, making it a great choice for ebb and flow systems.
Unfortunately, rockwool is not biodegradable so eco-conscious farmers might hesitate.
Plus, it requires being presoaked in water with a pH of 5 to 5.5 for 24 hours. Otherwise, its naturally high pH will make it inhabitable for plants.
Lightweight Expanded Clay Aggregate
Lightweight Expanded Clay Aggregate, also known as clay pebbles, are round pieces of heat-expanded clay.
Clay pebbles have a low CEC and WHC and a high AFP, making it difficult to over-water and easy to provide oxygen. It’s also reusable!
On the downside, clay pebbles are heavy and may drain too quickly for some systems.
As a result, this medium works best for deep water culture (DWC) systems, which keeps plant roots constantly exposed to water.
Cocopeat
Cocopeat is a natural fiber made out of coconut husks. The extraction of coconut fiber from husks gives us this by-product called coco-peat, which is a 100% natural growing medium. This cocopeat dried in the natural sun is processed to produce different items namely cocopeat block, coco peat briquettes, cocopeat tablets, etc.
Loose coco peat is often referred to as coco soil. Coco soil being a porous and well-drained medium, helps the plant to have strong roots, thus making it an excellent growing medium for hydroponics.
Perlite
Perlite is a volcanic rock and can be added to other growing mediums or used on its own.
Fans of perlite like that it’s lightweight and has a very low CEC and high AFP, making it easy to control nutrients.
It also absorbs water fairly easily, but not so well that there’s a high risk of overwatering. Therefore, this growing medium works best for wick systems.
However, perlite floats in water. As a result, it’s unsuitable for plant support in systems that submerge the growing medium, such as ebb and flow.
Vermiculite
Vermiculite is a popular hydroponic media favoured for its affordability. ... When used in hydroponics, vermiculite is often mixed with perlite if the media becomes too water logged. This improves aeration and drainage. In hotter climates vermiculite is often used by itself because of its higher water holding capacity.
Horticultural Foam
Also known as phenolic foam or peat foam, a horticultural foam is a synthetic product available as plugs and commonly used for starting seeds. It is designed to offer an optimal water absorption/retention to root aeration ratio. It is generally reusable for more than one growing season; be sure to check the manufacturer's documentation for the expected lifespan of specific brand name foams, as well as requesting specifics on compostability/biodegradability. Some are biodegradable in about 18–24 months.
Expanded Clay Aggregate
Expanded Clay Aggregates are also called Expanded Clay Pebbles or Expanded Clay Pellets and are better known in the Philippines as Hydrotons. They are brown light-weight aggregate with a nominal particle size of from 8 mm to 12 mm. It resembles the oddly shaped, semi-round pieces of clay-colored balls. Expanded Clay is non-toxic, disease-free, resistant to algae, chemically inert, and sterile with a natural pH. It has good insulating properties over a wide range of temperatures, will not compact, and is unaffected by frost.
Aesthetical look
One feature that makes the clay pebbles different is the fact, that they provide an aesthetical appearance to the pot, where they are placed. Their look is such that they would only enhance the beauty of the pot and not look out of the place. Also, they are maintaining a perfect temperature, humidity level, and drainage ensures, that the amount of effort required in taking care of them, is minimized.
Expanded Clay Aggregate is a great choice in growing plants for your landscape, as they are reusable, last a long time, and can be used in different hydroponic systems and different stages of plant growth. They do require a bit of effort and time to get the most out of them while protecting your mechanism but for many people, it is well worth it.
Comments