Soil for Microgreens - Which Media is the Best?
In a previous article, we showed without a doubt that growing microgreens in the soil is way better than on jute mats.
The next obvious step is to evaluate soil media to see which works best. Or at least begin the process to narrow down the choices.
We planted the same mass of Red Acre Cabbage microgreen seeds in the same volume of three soil media, pure coconut coir, a premium coconut coir-based mix, and a premium peat-based mix, to compare growth rates and quality of the harvested microgreens.
Not Really Soil - But Soilless Mix
When we say soil, what we really mean is using a soilless media. Soil, by definition, contains a mixture of organic matter, minerals, gases, liquids, and organisms.
However, to make reading (and writing) easier, when the text mentions soil, know that we're discussing are the following soilless mixes as shown above from left to right.
Coco Loco Potting Mix
Coco Loco is produced by Fox Farms and is a coconut coir-based potting mix. We use this soil mix in our microgreen trays and is also the soil that we sell in small volumes. We purchase Coco Loco in 2 cubic foot bags for between $19.50 and $21.00, currently.
We wouldn't expect anyone to purchase Coco Loco on Amazon because of the price (due to shipping a large bag), this is why we sell smaller bags for the home microgreen grower.
However, if you want to take a look, you can click the next image or this or this link.
When you purchase any coir product, use one that professional growers would buy, as the quality will be better.
Coco Loco Ingredients
Coco Loco is composed of the following:
The coir is triple washed to ensure a quality product with low salt content.
The mix is sterilized, not sure how that works with the bacteria and fungi. We'll research this more and let you know.
Happy Frog Potting Soil
Happy Frog is produced by Fox Farms and is a peat moss based soil mix. We purchase a 2 cubic foot bag of Happy Frog to use in our always on-going microgreen tests. We bought the bag from a hydroponic supply store for $20.
Happy Frog is sold in smaller bags. The link below and the image adjacent will take you to Amazon where Happy Frog is sold in a 12-quart bag.
Happy Frog Ingredients
Happy Frog is composed of the following:
Soil Type Summary
We want to see, by using side-by-side comparisons, which soil is better for microgreens. We are testing three soils, pure coconut coir (a sterile, non-nutrient based media), a coconut coir-based potting mix, and a sphagnum peat-based potting mix.
The test is limited to three soil media types due to space restrictions. Other media, such as vermicompost will be tested similarity with those that show the most promise in this test at a later date.
The Soil for Microgreens Test
In the test soil, we're growing Red Acre Cabbage microgreens.
We consider cabbage a quick-growing microgreen. We also realize that the nutrients in Coco Loco and Happy Frog might not be fully utilized in the short period the cabbage microgreens are in the soil.
Therefore, we will run a second test with a slower-growing microgreen, such as basil. We will, of course, link that article here when it's published.
Soil for Microgreens Procedures
Similar planting trays (same size, number of watering holes, etc.) are filled with each of the soil media types.
The same mass of Red Acre Cabbage seeds is sown in each tray that has been pre-wetted with the same volume of water. Here's how we plant the trays.
The trays are then covered with the same amount of weight during the blackout period.
Trays are placed under the same light in the same position and bottom watered in a larger 10 by 20 tray. More water is added to the watering tray than needed. After an hour, the excess water is removed from the watering tray.
Below are the results of the soil for microgreens test.
Soil for Microgreens Results
Day 0 - Seeds Sown
Soil for Microgreens Test - Blackout Period
All three trays of soil media planted with Red Acre Cabbage were placed in a 10- by 20-inch tray. A plastic cover is placed over the seeds, and a two and a half pound weight is added to the top.
Light is excluded during the blackout period by placing a tea towel on top of the seeded trays. The ambient temperature is between 75 and 80ºF, so a heat mat is not necessary.
Day 2 - Seed Germination
Day 3 - Rooted Seedlings
Day 4 - Remove from Blackout Period
Day 4 - Differences Are Apparent
There are noticeable differences in the rooting behavior of the cabbage seedlings as early as Day 2, and on Day 4 the rooting behaviors have expressed a physiology response in the plant.
The photos were taken immediately after the weights and covers were removed from the trays and blackout.
In the first photo, you can see that the seedlings in the pure coconut coir (left most tray) and to a slightly lesser extent the plants in the coir-based soil (middle tray) are more upright.
We believe the more upright behavior is because the roots have an easier time establishing themselves in the coir than peat. The seedlings in the coir and coir-based media are better anchored, allowing the plants to lift the weights and straighten out their stems.
The seedlings growing in the peat-based media can not leverage the soil to lift the weight and straighten themselves.
The trays will now be removed from the blackout period, and the LED light will be turned on for 15-hours a day.
Day 5 - First Day Under Light
Day 9 - Skip To The End
Best Soil For Microgreens - Discussion
It's a bit hard to tell from the photos which tray grew the best. But the images below are better because of the white background.
Microgreens will grow well in all three media types. We wouldn't call any of the trays bad. But the coconut coir and coir-based soil media grew larger microgreens over the nine days.
That isn't to say that it's terrible to grow microgreens in a peat-based soil. Only a different growing method might be needed.
But using the Home Microgreens growing method, microgreens grow better in coconut coir or coir-based soil media.
The photos below show the results in a better light.
Microgreen Size Comparison
Which Soil Would You Use?
If you grow microgreens, either at home or commercially, let me know what soil you use and why. Even if you use jute or some other mat material, please leave a comment below and let everyone know why.
There are many ways to grow microgreens, and it all depends on the growing methods and probably 25 other variables. However, we believe a coconut coir-based media is best, based on the results, for our recommended way of growing microgreens.
Spawning Other Articles
The results presented above will generate a few other articles.
We especially are interested in how well seeds germinate and grow into the coconut coir.
Links to the articles will be included in this post once they've been published. The topics we're thinking about now, to name a few, will be:
Don't miss a future article, click the button below to receive updates.
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Our Favorite Soil For Microgreens Is...
We prefer to use the coconut coir-based Coco Loco Potting Soil for microgreens. We think it allows for the perfect amount of water uptake without staying too wet. Also, the microgreens root quickly into the media allowing the young plant to anchor and absorb nutrients as the plant grows.
We like the looseness of the bagged soil, and nothing has to be done to the soil before using it (like hydrating coconut coir bricks).
That said, if we couldn't purchase Coco Loco locally, then it might be more economical to buy coconut coir bricks online. We will see how inexpensive the coir bricks are in a future post.
In summary, you can't go wrong with any of the three soils tested in this article. However, Coco Loco (coconut coir-based mix) appears to grow microgreens better than pure coir, or a peat-based soil mix.
What soil mix or fiber mat do you use to grow microgreens? Leave a comment and let us know! We can all learn from each other.
You can purchase small bags of coconut coir-based soil mix in the Home Microgreens Store. Click the Shop Now! Button below.
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