Which one will perform the best? 1) Worm castings, 2) Activated Charcoal, 3) Both 4) Neither?

I’m scheduled to give a “Tomato Talk” to a local group of community members who are interested in growing their own tomatoes from seed in the next 10 days and in the process for preparing for this talk, I thought I’d do a little soil test for what makes for a strong seedling and share it with y’all as things grow so that you can grow your health through gardening and learn tips for what I learn along the way. 😉

I took four (4) 4-pack planting trays and used the same batch of sifted soil for all four packs. The control 4-pack is straight up soil only. The second 4-pack I amended the soil with worm castings only. The third 4-pack I amended the soil with activated charcoal from a company I heard about and am trialing their product before bringing it to sell in our store and online. The fourth 4-pack soil is amended with the same ratio of worm castings as the second 4-pack as well as the same ration of the third 4-pack of soil with activated charcoal (so this final 4-pack has both amendments in it.)

A glimpse of our current seedling test subjects.

I then repeated the same amendments in another batch of similar soil, but put it in a soil block and amended certain soil blocks with worm castings only and activated charcoal castings only and a mix of both worm castings and activated charcoal. I also included rock wool just to compare growth of seed in this substrate as well. The rock wool will need to have kelp diluted and added to it as the seedlings grow as the rock wool is pH neutral and is devoid of nutrients.

For plants, I chose seed that was from the same lot, same harvest, same parent plant. All seed is our homegrown line of seed that we’ve saved and developed season after season, so I am confident that we have good strong seed stock to run the test. I chose to plant microdwarf tomatoes, because we are in the middle of winter here in Atlanta, Georgia and I can grow micro-dwarf tomatoes indoors under lights and evaluate results before our busy season of the summer harvest begins. We selected different micro dwarf tomato cultivars including Florida Petite Microdwarf Cherry Tomato, Rosy Finch Microdwarf Cherry Tomato, Aztek Microdwarf Cherry Tomato and Venus Microdwarf Cherry Tomato.

Rosy Finch Micro Dwarf Tomato Seedlings pop out of the soil ready to reach for the light.

This is a Fiskars Soil Block that is a plunger style and easy to use. You can make soil blocks of four or one larger soil block.

Setting the first soil block with the other four 4-pack trays already finished and planted.

Small bits of Activated Charcoal in equal parts and mixed thoroughly in each 4-pack of soil as well as equal parts of worm castings mixed well in 4-packs of soil keeping things as consistent as possible. We are testing to see if the activated charcoal makes any significant difference before carrying a product in our store. Stay tuned!

To gauge results, we will weigh all produced fruit and count the number of blossoms and the number of final fruit set by each tomato plant. I will do my absolute best to give equal amounts of water by first measuring what each plant is given and offering the same amount to each plant.

My hypothesis is that the air pruning action of the soil blocked starts will produce stronger seedlings for transplanting in the long run because when that root hits the air, it will signal to the plant to produce roots on the interior of the soil elsewhere. More roots will mean the plant has more opportunities to take up moisture and nutrients in the long run. I also think the soil block with BOTH worm castings and activated charcoal will perform the best because the worm castings will further any biological activity that may be happening within the soil and “cling” to the activated charcoal which the plant can tap as it needs.

That’s my best guess, but I could be wrong! We shall see what plays out in our little science experiment. What do you think will perform the best and why? Tell us in the comments below!

Happy Growing!
Erin