Requirements of a growing medium:
The term ‘substrate’ is also used and means the same thing. In the UK some people still use the term ‘compost’ in the same context, however a compost is technically the product of a composting operation (eg the compost heap at the bottom of the garden) and can therefore be a misleading word to use. A composted material may be a component of a growing medium but peat is not a product of composting and nor are many other ingredients we use. In Holland the term ‘potting soil’ is often used instead of ‘growing medium’
The term ‘growing medium’ is used to describe the material used in a container to grow a plant.
Manufacturers also need growing media to be physically and chemically stable from the time of production until the time of use (this can be many months for retail products). The bulk density (weight) of the ingredients used is also important because this affects transport costs, a major part of the total cost of production and delivery to the end customer.
To be safe when handled by people
To be free of plant pathogens, pests and weeds
There are many different ingredients that can be used to make a growing medium; different parts of the world have developed media based on local availability of various raw materials. Such materials can be inorganic (eg rockwool, perlite) or organic (such as peat, bark). Growing media are often formulated from a blend of different raw materials in order to achieve the correct balance of air and water holding capacity for the plants to be grown.
To hold sufficient available water
To hold sufficient available nutrients
What Is Growing Medium? The term ‘growing medium’ is used to describe the material used in a container to grow a plant. The term ‘substrate’ is also used and means the same
Rockwool is one of the most common growing media’s used in hydroponics. Rockwool is a sterile, porous, non degradable medium that is composed primarily of granite and/or limestone which is super heated and melted, then spun into a small threads like cotton candy. The rockwool is then formed into blocks, sheets, cubes, slabs, or flocking. Rockwool sucks up water easily so you’ll want to be careful not to let it become saturated, or it could suffocate your plants roots, as well as lead to stem rot and root rot. Rockwool should be pH balanced before use. That’s done by soaking it in pH balanced water before use.
Good source to find pine shavings are pet supply stores. Its used for things like hamster and rabbit bedding. Just make sure to read the package to be sure it doesn’t have any chemical additives like fungicides or odor inhibitors. You should be fine if it states it’s organic. Another good cheep source for pine shavings is at feed stores, it’s also used as bedding in horse stalls and they sell it by cubic yard. If you have a choice get the largest partial size you can. The larger the air pockets between the shavings, the better aeration to your roots.
Composted and aged Pine bark
Pine bark is one of the first growing media’s used in hydroponics. It was generally considered a waste product, but has found uses as a ground mulch, as well as substrate for hydroponicaly grown crops. Pine bark is considered better than other types of tree bark because it resists decomposition better, and has less organic acids that can leach into the nutrient solution than others. Bark is generally referred to as either fresh, composted, or aged.
River rocks are not porous, therefor it doesn’t hold and retain moisture in the root zone of hydroponic systems. Rock is uneven so it has a lot of air pockets between the rocks so the roots can get plenty of oxygen, but water easily drains down to the bottom. Rock won’t wick up moisture either, so you will need to adjust your watering schedules so the roots don’t dry out between watering’s. You can mix in some coco chips or other growing media that holds moisture with your rock to aid it in holding onto moisture longer.
When using sand as a growing media you will want to use the largest grain size you can get. That will help increase aeration to the roots by increasing the size of the air pockets between the grains of sand. Mixing Vermiculite, Perlite, and or coco coir with the sand will also help aerate. You will also want to rinse the sand well before use to get as much of the dust particles out of it as you can. One big downside to using sand as a growing media for hydroponics is that it is very heavy. 3-4 gallons of wet sand can weigh up to 50lbs. So you won’t want to be moving it once you get it set up. Or use it in a ratio of something like 20%-30% sand and the rest Vermiculite, Perlite, or another type of growing media to reduce weight.
River rock is common and easy to find in home improvement stores, as well as even pet supply’s stores (with the fish and aquariums). River rock is fairly inexpensive (depending on where you get it from), and comes in many different sizes. River rock is rounded with smooth edges from tumbling down the river. Though manufactured river rock is rounded using large mechanical tumblers, it has the same end result with smooth edges.
Drip systems are fairly easy to control moisture in. As long as you design it so it has good drainage, and limit water pooling at the bottom you should be able to keep your growing media from being too soggy. We like to use river rock at the bottom to aid drainage, and keep the growing media from sitting in a pool of water at the bottom.
Coco Fiber Coco Chips
“Coco coir” (Coconut fiber) is from the outer husk of coconuts. What was once considered a waste product, is one of the best growing mediums available. Although coco coir is an organic plant material, it breaks down and decomposes very slowly, so it won’t provide any nutrients to the plants growing in it, making it perfect for hydroponics. Coco coir is also pH neutral, holds moisture very well, yet still allows for good aeration for the roots. Coco fiber comes in two forms, coco coir (fiber), and coco chips. Their both made of coconut husks, the only difference is the particle size. The coco fiber particle size is about the same as potting soil, while the coco chips particle size is more like small wood chips.
Using the polymer crystals for hydroponics allows for some of the simplest hydroponic system designs. Even on the slimmest of budgets. Simply soaking some water absorbing crystals in nutrient solution, then setting them in a container and placing your seedling’s in it, you’ve got a hydroponically grown plant. You don’t need any pumps. Just make sure there are holes in the bottom of your container, and just place your container in nutrient solution once or twice a week to re-hydrate the crystals.
Learn the types of Growing mediums used for Hydroponics, their advantages, disadvantages and even if you need to use any at all.