Which Microgreen Soil is Best -Part 2
In that test, we decided that a coconut coir based soil mix outperformed pure coconut coir, and a peat-based soil mix to use as a microgreen soil.
However, we haven't dismissed pure coconut coir yet. The pure coconut coir performed well, and it may be less expensive to use as a microgreen soil. Coir also holds water longer, so less time is spent caring for your microgreens.
But what about slow-growing microgreens?
Can slower growing microgreens such as basil grow for 20 or more days in the nutrient-poor coconut coir?
The coir and peat mixes are amended with natural nutrient-rich ingredients. Will these nutrients help slow-growing microgreens grow faster and produce better plants?
In this article, we will plant and grow Dark Opal Basil in three kinds of microgreen soil media and document the results.
Day 0 - Planting Basil Seed in Microgreen Soil Media
In the photo above, 1.0-gram of Dark Opal Basil Seeds is sown on three types of microgreen soil media. From left to right, pure coconut coir, a coir-based potting mix, and a peat-based potting mix.
Click on any photo in the article to expand the size for better viewing.
The basil seeds and microgreens will be germinated and grown exactly as the cabbage microgreens were in the test described in The Best Soil for Microgreens.
All of our microgreen soil and jute media articles are listed below if you'd like to compare this test with the others.
In all of the photos below, the three microgreen soils are shown in the same order.
The first tray contains pure coconut coir.
Second, is coconut coir based potting mix produced by Fox Farms, called Coco Loco or Bush Doctor Coco Loco.
Lastly, a peat-based potting mix, again produced by Fox Farms, called Happy Frog.
Remember, pure coconut coir is nutrient poor and we question if plants can grow well in it for 20 or more days without adding liquid fertilizer.
The other two potting mixes contain natural mineral and organic amendments. These amendments are listed in the previous article, The Best Soil for Microgreens if you're curious about the amendments.
We believe these two potting mixes will perform better than pure coir.
Below is a chronological sequence of photos showing the basil growth stages during the test.
Day 4 - Basil Microgreens Placed Under Light
On day 4, the trays of basil are removed from the blackout period and spaced out in a watering tray under an LED light with a spectrum of 4,000K.
The growth of the microgreens are similar, but those grown in pure coir are less leggy, more upright, and appear better rooted in the microgreen soil media. This is identical to the first test, where the cabbage microgreens anchored themselves quicker in the coir than the other media.
Day 9 - Equal Growth in the Cotyledon Stage
Growth during the cotyledon stage is about the same for all three microgreen soil media.
However, you can see that the basil grown in the peat-based microgreen soil does have slightly smaller leaves.
The faster-growing cabbage microgreens in the first test showed the same pattern, but with more variance.
Also, notice that the peat-based microgreen soil media is dryer than either of the coir-based trays (first photo shows this well). During the test, we bottom water the microgreens in a level watering tray. Therefore, all three potting mixes have the opportunity to draw up equal volumes of water.
You can see that peat doesn't draw water as well as coir.
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Day 12 - Growth Differences Appear
In the Red Acre Cabbage experiment, the microgreens were harvested on Day 9. Both coir-based soil media produced more cabbage microgreens than the peat-based soil media.
But here on Day 12, the basil in pure coconut coir is lagging behind both potting mixes.
The basil microgreens growing in pure coconut coir (first close-up photo) haven't developed true leaves.
As you can see in the middle photo, the first true leaves have not only formed, but are growing more prominently in the coir-based potting mix than the others.
In the last photo, you can also see small true leaves forming on the basil growing in the peat-based mix.
Is the reason for the developmental difference because the smaller basil seeds (compared to cabbage seeds) don't contain as much starch? And the basil seedlings are using the available nutrients in the potting mixes to grow?
We believe so.
We also believe the basil plants are larger in the Coco Loco potting mix because plants seem to develop roots quicker in coir than peat.
Day 19 - Better Color & Size in Coir-based Potting Mix
The middle tray is the basil grown in the coir-based microgreen soil. It's growing better (more color) and larger than those grown in pure coir (left tray) and a peat-based potting mix (right tray).
The basil grown in pure coir is lagging behind the other two, in development, size, and color.
The basil in the peat-based media isn't that far behind the middle tray. We'd be happy with those microgreens if the middle tray weren't there.
Day 25 - How Things Change - Too Little Too Late?
Six days later and the basil microgreens grown in the peat-based potting mix have overtaken the coir-based potting mix in size. But they haven't colored as nicely.
The microgreens grown in pure coir lag behind both of the potting mix microgreen soil media.
We aren't quite sure why the turn of events.
One would think that the kelp would provide more plant nutrients (NPK) than leonardite, which is more a soil conditioner than fertilizer.
Maybe the humic acids that leonardite supposedly adds to the mix is the difference?
Will have to put more thought into the reasons.
Which Microgreen Soil Media Is Best for Slow-growing Microgreens?
It appears that slow-growing microgreens, those that are harvested after 20-days or longer, do better in a peat-based potting mix. The coir-based potting mix is not quite as good as the peat-based mix.
Pure coconut coir is definitely not the microgreen soil media to use for slow-growing microgreens.
Where Does This Leave Us with Microgreen Soil?
As it stands right now, at least after this experiment, we'll continue to use the coir-based potting mix (Coco Loco) for all of our microgreens.
Pure Coconut coir can't grow slow-growing microgreens, and the peat-based potting mix doesn't grow quick-growing microgreens very well.
Coco Loco grows both quick-growing and slow-growing microgreens best on average. So instead of buying both Coco Loco and Happy Frog, we'll plant slow-growing microgreens in Coco Loco and let them grow an extra couple days.
However, we have more tests and experiments we want to run on this topic. Below is a list of articles we plan on publishing. We may also add to this list as we go.
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Our Favorite Microgreen Soil 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 we use 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.
You can't go wrong with any of the three soils tested in this article. All of them will grow microgreens, it's a matter of how long they need to stay in the tray.
However, Coco Loco (coconut coir-based mix) appears to grow quick-growing microgreens better than the other two. Also, slow-growing microgreens do well in it as well.
Question For You
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.
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