Container mix comparison question & observation

19 years ago

Have a question on root development below.

I have 2 homemade self watering containers with different mixes in them to do a comparison.

A. 1:1:1 peat/vermiculite/compost, 19 gallon rubbermaid container. Early girl tomato.

B. 3:2:1 small pine bark nuggets/turface/peat, 5 gallon container. Early girl tomato.

In container A, I'm only watering the reservoir and letting it dry out before each watering. In container B, I'm doing top watering and the letting the reservior fill up and then mostly dry out before top watering again.

The tomato in B was smaller when first planted but now is a little bit bigger ~2feet tall.

However, in the middle of the day on hot/warm days the B tomato slightly wilts. Tomato A does not wilt. The soil in B is still wet and the reservior is full when the slight wilting occurs. If I water B then in the middle of the day (even though the soil is wet and reservior is full) the plant recovers and no wilting.

Also I've scrapped away some soil to (carefully) look at the root development of each.

In A, there were no roots until about 1.5 to 2 inches down. Very white healthy roots there. (I stopped looking as soon as I saw the first roots).

In B, as soon as I scrapped away a little soil, virtually on top, there were many very white healthy thick roots at the top of the soil.

My unscientific conclusion would be:

In B, while the soil is well aerated, it is too coarse for ultimate development. The roots can't get hold of enough soil surface area to supply it with water in mid-day heat.

While B has grown slightly faster when small, it could experience slower growth as it gets bigger (this will be interesting to see what happens).

In A, the plant can get its roots around all the soil it needs and so it doesn't need the need the extensive roots at the soil surface that B does. But the lack of soil air is slowing its growth.

I can't top water these every day and certainly not in the middle of the day, so I'm thinking next year maybe a mix of 1:1:1 of bark/turface/peat might be better.

Does anyone with knowledge and experience in this "root development area" have any comments insights. Are my conclusions on track?

Also I believe remembering reading that Tapla didn't use the highly aerated mix for vegetables. Why not?

Thanks EM

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Comments (3)

Pyewacket
19 years ago
You really can't draw conclusions about the soil mix because you've introduced a confound into your experiment when you used two different sizes of containers. A 5 gallon container will have more difficulty maintaining even moisture when compared to a 19 gallon container, so the fact that your 5 gallon container experiences some mid-afternoon droop can't be attributed to the soil mix alone. It's more likely heavily affected by the container size.

In order to adequately compare the two soil mixes you would need to use comparable containers at the very least, and comparable watering practices on like soil mixes as well. You would need four containers to run this particular experiment, all of the same size. Use the same soil mix in two, your 1:1:1 mix in two same-size containers and then your 3:2:1 mix in the other two. Use watering technique A on one of each soil mix, and watering technique B in the remaining two, so that each soil type gets both the A treatment and the B treatment.

Or you could simplify the experiment and test only the soil mix, which would require only 2 same-size containers. But if you're really curious to know what's best, different watering treatments could have different effects when combined with soil type. So the 4 pot experiment is the most informative.

But right now you can't conclude that soil mix is having the main effect on the plant because it's so strongly affected by container size.

Sojourner
wi-northernlight
19 years ago
I think that zensojourner makes a valid point about container sizes. However, you can certainly make a comparison between your 5-gallon SW containers and other peoples 5-gallon SW containers, like the Earthbox, Gardeners Supply SW planter, etc.

If others are using a similar mix to your "B" mix (seems pretty close to Al's recipe for container soil, it seems thay could comment on their wilting problems, if any. If Al's soil mix isn't appropriate for SW containers, that would sure be nice to know, as it seems a lot of people are using it. Maybe some experience SW conatainer users could comment on soil mixes that work well for tomatoes.

Nlight
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emgardener
Original Author
19 years ago
Hello,

This year I compared the two mixes in self watering containers. The unscientific results are:

For the bark/turface/peat mix, I got tired of self watering it every day. It needed daily watering, otherwise the tomato would wilt, even if the reservior was full. So I used an automatic dripper to automate the watering. This resulted in continuous overwatering and the plant is sickly with many yellow leaves & few fruit.

The traditional peat/vermiculite/compost container, I hooked up to a self waterer that kept the reservior full at all times (but did not overflow). This plant is doing great, many fruit, green leaves.

Question: Has any one else tried "Al's mix" in a self watering container with success. If so what did you do.

Justaguy, I believe a read you tried it this year? What happened?

Next year I'm still motivated by seeing the great root structure in "Al's mix" plant. And when handwatered, that plant was doing the best. So, I'll try another automatic watering system. Probably keep the reservoir on a self-fill system, and then add a pump that will daily pump the reservoir water to the top of the container. Not a simple system, but I really want to see the ultimate container tomato grow.