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Mineralized topsoil


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#1 Guest_Newt_*

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Posted 02 November 2009 - 02:18 PM

I've been reading a bit on some planted aquarium fora about mineralizing topsoil for use as a planting medium. The process simply involves alternately inundating and draining a batch of topsoil until it becomes grainy and "mineralized", or stripped of organic macromolecules. The supposed mechanism is consumption of the organic matter in the soil by heterotrophic bacteria. The claimed benefits include lesser likelihood of algal blooms after addition to the aquarium.

I'm a bit dubious about the whole thing- whether heterotrophic bacteria can actually eliminate a significant amount of organic matter in a short span of time, whether the inundation/draining process would actually hasten this action, and whether non-macromolecule-containing soil would actually make much difference to algae.

Do any of you have any experience or knowledge relating to this topic? I'm rather curious about it.

#2 Guest_fundulus_*

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Posted 02 November 2009 - 02:58 PM

My reaction is, did anybody actually test this idea experimentally, or is this a feel-good "natural" process someone is invoking out of the blue? In truth, many bacteria are notoriously difficult to culture.

#3 Guest_Newt_*

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Posted 02 November 2009 - 03:07 PM

Everything I have found on the web goes back to this simple how-to article by Aaron Talbot: http://www.fshfanatic.com/?p=84. I have seen nothing that looked at the in-depth biology or chemistry of the process nor that directly compared "mineralized" to non-mineralized soil in the aquarium.

#4 Guest_nativeplanter_*

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Posted 03 November 2009 - 01:41 PM

I've seen the description of the method of which you post, albeit it has been a very long time since. I have seen no real data one way or the other. I am also dubious. In fact, I have at times added organic matter to my substrates. I'll have to go and look at it again.

#5 Guest_Newt_*

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Posted 03 November 2009 - 02:15 PM

I guess I will have to be the guinea pig! I have a couple of 10 gallon aquaria lying idle. I think I will set them up with "mineralized" and unmineralized topsoil and see how they compare with regards to algae growth. Obviously this won't be a very strict experiment, but it'll provide some anecdotal info at least...

#6 Guest_nativeplanter_*

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Posted 03 November 2009 - 03:21 PM

I guess I will have to be the guinea pig! I have a couple of 10 gallon aquaria lying idle. I think I will set them up with "mineralized" and unmineralized topsoil and see how they compare with regards to algae growth. Obviously this won't be a very strict experiment, but it'll provide some anecdotal info at least...


I'm sure you'll have fun with it. Problem is, it won't really give any more information than the anecdoteal evidence that we already see.

There are a number of things I would like to test if I had spousal permission. I've pictured soda bottles (tops cut off), set up with enough of them to do statistical analysis to see if something really works. Here's an example: If I put say, 3 inches of sand and one gold fish in each bottle, and wood chips under the sand in half the bottles, would these bottles result in lower nitrate readings (presumably from denitrification)? But I don't have permission for such a setup...

#7 Guest_Newt_*

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Posted 03 November 2009 - 06:03 PM

That's a better idea. I probably could manage such a setup. I have a 4-foot shoplight, counter space, and scads of soda bottles (I've got to quit drinking that swill). Do you suppose I should inocculate each cup with a standardized amount of algal slurry? This could help to eliminate the element of chance in which bottles are colonized.

#8 Guest_nativeplanter_*

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Posted 03 November 2009 - 08:07 PM

Do you suppose I should inocculate each cup with a standardized amount of algal slurry? This could help to eliminate the element of chance in which bottles are colonized.


Hmm. Not sure. You would somehow have to be sure that the slurry amounts contained the same number of individual cells or chlorophyll content or something like that. Got a magnetic stirrer?

More important I think is to figure out how to measure the results in a meaningful way. Mass? Surface area covered? Mass is probably the way to go if you have access to the right equipment (and I think you do, right?)

#9 Guest_Newt_*

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Posted 03 November 2009 - 10:16 PM

I can request use of the equipment. I could get dry mass using a crucible. I don't think it will be necessary to go all the way to ash-free dry mass; organic content should be similar in all samples. Alternatively I could re-slurrify each sample, and use a spectrophotometer to estimate chlorophyll a content. I suppose I could even centrifuge the samples hematocrit-style and look at relative volume of alga.

Since the stuff's main purpose is to provide nutrients to plants, I would also like to look at comparative plant growth between the two substrates. I will have to collect plants as all the local pond shops have closed for winter; perhaps Hydrilla would be a good, and expendable, test subject. I think plant volume would be the easiest measure to take for purposes of before/after comparison.

So, two variables, each with two states: substrate=natural soil, substrate="mineralized" soil, plant=present, plant=absent. That makes four possible combinations, and I will want at least 10 replicates of each. That's 40 containers; new plastic cups are probably preferable to used soda bottles. 40 cups should still fit comfortably beneath my shop light, and any irregularity in light distribution should be corrected by randomized placement of the replicates.

Two questions: how long? And should I attempt to kill existing algae on the Hydrilla? My inclination is not to, as strands from a single clump should have similar periphyton makeup. Perhaps a third variable could compare Hydrilla treated with ome algicide to untreated Hydrilla to make the plant/non-plant comparison more valid.

#10 Guest_Newt_*

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Posted 04 November 2009 - 09:40 AM

Nuts, almost forgot my controls. Cups with just water or cups with a nutrient-free substrate equal in amount to the test cups? Should I also use some cups lacking the algal slurry inoculation?

This project is going into a death spiral of elaboration, just like everything I try to do. :D

#11 Guest_nativeplanter_*

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Posted 05 November 2009 - 02:21 PM

No, you have your controls. You are basically comparing two populations to see if they are different. Regular topsoil without plant is a control, mineralized topsoil without plant is the independent variable. Same for with plant - regular topsoil with plant is the control, mineralized topsoil with plant is the independent. Think of it like a drug trial. This is because you want to know if these setups are significantly different from one another, not whether they are significantly different from plain water. So long as all of the other variables are standardized, you are all set.

edit - are these cups going to be big enough? I was thinking soda bottles because you could probably get a liter of water in there.

#12 Guest_Newt_*

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Posted 06 November 2009 - 12:29 PM

Oh, you meant the big soda bottles...I mostly have 1/2 L and 20 oz. bottles. I'd end up having to buy some kind of containers in any case. I'm also not sure I have adequate counter space and lighting for 40 1 L containers, so I might have to cut down on the number of replicates. Do you think the container size will matter that much?

#13 Guest_nativeplanter_*

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Posted 06 November 2009 - 01:16 PM

Actually, I meant 2 liter, so you could get a liter of water in after adding a decent depth of soil.

This explains why I do not have permission to set this up...

Don't know if it would make a difference or not. I was just thinking that it would more closely replicate an aquarium situation if you could put 3 inches of soil on the bottom, then gravel, then a good number of inches of water.

I've been thinking about this more. Really, I just think they are removing nutrients from the substrate. This would probably lead to less algae in the beginning, when the plants haven't really established themselves yet. Thinking it would be a lot easier to just choose a less fertile substrate and skip the whole procecure. But I'm still curious as to what experimental results would look like.

#14 Guest_Newt_*

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Posted 06 November 2009 - 01:37 PM

I dug up about 2 cubic feet of clayey topsoil yesterday. I'll go ahead and start the mineralization process and see what happens. I wonder what, if any, effect the process has on denitrifying bacteria in the soil?

#15 Guest_nativeplanter_*

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Posted 06 November 2009 - 01:56 PM

Before you start, homogenize the soil you have, then split it into two so that both soils have the same source characteristics.

#16 Guest_Newt_*

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Posted 06 November 2009 - 02:19 PM

Will do.




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