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The Top 5 Hydroponic Growing Mediums You Should Use
Hydroponics is a farming method that doesn’t require soil to grow plants or foods. Soil is not used in this form of farming. Other hydroponic growing mediums are used instead
Hydroponics is a farming method that doesn’t require soil to grow plants or foods. Soil is not used in this form of farming. Other hydroponic growing mediums are used instead. This article is going to cover the five best hydroponic growing mediums to use for your garden.
Perlite
Perlite is a volcanic rock that is exposed to high heat to turn it into a lightweight, porous medium. You can mix perlite in with other mediums or use it on its own. This porous medium is well known for its high water retention ability, and it is effective at retaining oxygen due to its porousness. The downside to perlite is that it is lightweight, which can cause it to float in high water settings like with ebb-and-flow systems. It’s better to use perlite in hydroponic systems with draining systems.
Coco Coir
Coco coir is one of the hydroponic growing mediums that has become more popular to use. Coco coir is grounded coconut husks and is a reusable medium, which helps create less waste. This medium effectively retains water to help hydrate your plants and is a great medium for beginners since it looks like soil. However, it isn’t soil and still requires nutrients and a controlled pH level.
Clay Pellets
Clay pellets are another popular hydroponic growing medium because of its porous material. A benefit of using clay pellets is that they are pH neutral, and they quickly soak up excess moisture. Clay pellets are reusable as long as you clean them between every growth cycle. It’s best to use clay pellets when you’re having issues with draining, but be careful clay pellets can drain and dry very quickly, which may dry out your roots.
Starter Plugs
Starter plugs are a newer hydroponic growing medium that is made from organic compost. This sponge medium is useful when you are growing seedlings or cloning, so you can later incorporate them into your hydroponic systems.
Rockwool
Many hydroponic growers use rockwool as their go-to medium. Rockwool is a melted rock that’s spun to create thin, long fibers, which are pressed into a cube shape. You will have to balance its pH before using it by soaking it in pH balanced water. Since it retains water so effectively, you will have to make sure it doesn’t oversaturate your plants. It’s an effective medium to use to ensure your plants get a majority of the necessary nutrients. However, it isn’t a biodegradable medium, and you do have to balance the pH before each use.
Knowing which hydroponic growing mediums to use can be a tough choice since there are so many options available. If you want to learn more about innovative farming methods, sign up for our microgreens class to learn more! Or, you can become a patron member to See Behind the Greens, where you’ll witness how food can be grown in closets, kitchen counters, living rooms, and more so you can learn how to do it too!
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Disease-Causing Bacteria Can Grow on Hydroponic Microgreen Mats
Salmonella enterica and Listeria monocytogenes are two bacteria that can make you sick when eating contaminated produce. It turns out, some microgreen grow mats might be a breeding ground for these bacteria
Posted on July 2, 2020, by Gina Misra
Salmonella enterica and Listeria monocytogenes are two bacteria that can make you sick when eating contaminated produce. It turns out, some microgreen grow mats might be a breeding ground for these bacteria.
You may be like a lot of people and associate foodborne illness with eating improperly cooked meat. Did you know that raw vegetables can also carry foodborne illness? Bacteria and viruses get on produce in a variety of ways: by food handlers, contaminated water, or soil fertilized with untreated manure. Romaine lettuce grown in Arizona made the news in 2018 because of widespread E. coli contamination. Sprouts, another popular health food, have been involved in 74 outbreaks of (mostly) Salmonella since 1973. Turns out these nasty pathogens are not just reserved for chicken and beef! There is no cooking step to kill the bacteria or virus on produce before it goes into your salad. Sometimes washing doesn’t even help, so prevention is key.
Microgreens are a hot new leafy green on the market. A microgreen is the first 2 to 3-inch (5 to 7-cm) tall shoot from a germinating vegetable seed. They are grown indoors in trays or hydroponics systems in soil, soil-substitutes, or without any rooting medium at all. Scientists understand a lot about how bacteria get to leafy greens from soil, but little about contamination in indoor farms. Are indoor farms safer if they don’t use dirt? We wanted to find out.
This is what a typical microgreen hydroponic system looks like. Source: Wikimedia Commons, by Kchittock0511 / CC BY-SA
Microgreen growers do use soil. However, they also use materials such as coco coir (made from coconut husks), Biostrate(TM) mats, plastic, perlite, rice hulls, and hemp in soil-free indoor systems. Our hypothesis was that if soil can transfer bacteria to lettuce, other growing materials can too.
E.coli and Salmonella survived better in hydroponic nutrient solution compared to soil, so we wondered if there would also be differences among soil-free materials. Within the last few years, there have been close to 10 microgreen recalls over diarrhea-causing Salmonella and Listeria monocytogenes found during routine testing. So, we decided to compare the survival of these two pathogens among popular soil-free growing materials to see if the bacteria lived longer on any of them.
An example of a Biostrate mat. Source: The author | Creative Commons Share Alike 4.0
We watered multiple samples of coco coir, Biostrate(TM) mats, hemp mats, and peat-based potting mix and contaminated them with Salmonella and Listeria monocytogenes. To imitate microgreen growing conditions, we left them on the lab bench for 10 days. We took samples from the mats on the first day, and then at 24 hours, 3 days, 6 days, and 10 days to measure the growth of bacteria. Each sample was spread onto Petri dishes containing a gel called agar, enriched with nutrients preferred by each species. The idea behind this classic microbiology technique is that if any cells from the samples were viable, they would multiply on the Petri dishes and form colonies. The colonies are easy to see with the naked eye, and each represents one cell from the original sample.
We found out that Biostrate(TM) mats and hemp mats supported the growth of these two pathogens, while coco coir and peat potting mix did not. In fact, on Biostrate(TM) and hemp, Salmonella and Listeria levels increased after 24 hours and then maintained their original levels for 10 days. On peat and coco coir, Listeria began to die off after the third day and was undetectable on coco coir by the 10th day. Salmonella survived better on all the materials, but on the 10th day, there were 10 times fewer colonies on peat and coco coir compared to the two mats.
Both pathogens showed poorer survival on peat and coco coir compared to no media at all. That means there may be some feature of the peat and coco coir that suppresses the growth of these bacteria. Understanding if that is true, and if so, what exactly that feature is will require more experiments.
It is necessary to point out that because this experiment did not involve microgreens, we still don’t know if microgreens grown in Biostrate(TM) and hemp actually do take up greater amounts of bacteria. These tests are underway! However, this preliminary information may be useful to indoor growers. Until we know more, microgreen growers may want to avoid using fibrous mats, perform additional sanitation steps, or do more testing to keep their customers safe.
Posted in Agriculture, Biology, By Science Writers, By Scientists, Food Science, Microbiology, Science NewsTagged agriculture, Biostrate, coco coir, contamination, food safety, food science, growing media, hemp, hydroponics, indoor farming, leafy greens, Listeria, Microgreens, peat, Salmonella
Study Information
Study published on: May 12, 2020
Study author(s): Gina Misra and Kristen E. Gibson
The study was done at: University of Arkansas
The study was funded by: National Institute of Food and Agriculture, U.S. Department of Agriculture (USDA NIFA) and University of Arkansas
Raw data availability: Available from the author upon request by email.
Featured image credit: Jenny Nichols WallpaperFlare.com