Dried Leaves As Fertilizer? - The Planted Tank Forum
 
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post #1 of 13 (permalink) Old 12-06-2015, 02:57 PM Thread Starter
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Dried Leaves As Fertilizer?

I've been researching the Nutrient Makeup of dried leaves to see if they can be used as fertilizer in the aquarium. From what I have read, there seems to be good reason that dried leaves in aquariums will provide nutrients for plants. Just how much nutrient is the question. Does anyone have experience with this? I found this interesting site listing the nutrient of dried leaves:
Plant Nutrients in Municipal Leaves
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post #2 of 13 (permalink) Old 12-06-2015, 04:06 PM
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Look at the chart they post.

Dried leaves are roughly 50% carbon.
As this is released it becomes a significant source of CO2 in a low tech or Walstad tank.

All the other nutrients are at such low levels, that while they are present, they are released so slowly that they almost do not count. You will get more benefit from the fish food you add, whether it is digested by the fish or by microorganisms, as a source of macros and micros.

An alternate way of using leaves is to compost them first. Then use the compost in the tank blended with the other substrate materials. There is less bulk doing it this way, so you can essentially add more leaves. Part of the problem with this is that some of the nutrients may be lost in the composting process, perhaps leached out of the compost pile and into the soil below.

One of the ways leaves benefit agriculture is that they encourage soil microorganisms and improve the structure of the soil, which improves the air/water exchange in the soil. This is a really important thing in agriculture (and in your own landscape) so I am not saying leaves are no good. They are very good- I just got through rototilling about 4" of leaves into my own vegetable boxes. But as a soil amendment, a source of organic matter. Not as fertilizer.
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post #3 of 13 (permalink) Old 12-06-2015, 04:46 PM Thread Starter
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Originally Posted by Diana View Post
Look at the chart they post.

Dried leaves are roughly 50% carbon.
As this is released it becomes a significant source of CO2 in a low tech or Walstad tank.

All the other nutrients are at such low levels, that while they are present, they are released so slowly that they almost do not count. You will get more benefit from the fish food you add, whether it is digested by the fish or by microorganisms, as a source of macros and micros.

An alternate way of using leaves is to compost them first. Then use the compost in the tank blended with the other substrate materials. There is less bulk doing it this way, so you can essentially add more leaves. Part of the problem with this is that some of the nutrients may be lost in the composting process, perhaps leached out of the compost pile and into the soil below.

One of the ways leaves benefit agriculture is that they encourage soil microorganisms and improve the structure of the soil, which improves the air/water exchange in the soil. This is a really important thing in agriculture (and in your own landscape) so I am not saying leaves are no good. They are very good- I just got through rototilling about 4" of leaves into my own vegetable boxes. But as a soil amendment, a source of organic matter. Not as fertilizer.
So, .0098 mg/L of iron, if my math is correct? For comparison, API Leaf Zone has .3906 mg/L iron. About 60 liters of leaves would come closer to the amount of iron in API Leaf Zone? Ha! Nevermind then. :} But as you say, there are still some benefits to leaves. I'll 'leave' it at that.

Last edited by AWolf; 12-06-2015 at 05:22 PM. Reason: Clarification
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post #4 of 13 (permalink) Old 12-06-2015, 06:42 PM
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I wonder what would happen if you were to let them dry out and then pulverize them to powder? Would they actually dissolve?

Anyway, I have a Geobin that I'm using exclusively for leaf composting this year for my raised beds. I suck them up and bag them with a lawnmower, which shreds them pretty nicely (though I've considered using a mulching blade to further reduce the size - maybe next year), and dump them in the bin. It would go faster If I turned the pile from time to time, but I'm lazy. As it is, I check with a pitchfork every once in a while, and the further down I dig, the more "dirt" I see. It won't do too much for the next several months unless I mix it up and add air and water (the inside of the pile will never freeze solid in this zone). It should make some really nice compost for the spring.

I have it next to another bin where I dump grass clippings, woodchips, garden waste, and kitchen scraps. Come spring, I'll compare.

Anyway, I wonder what the difference would be if you composted them before adding to the substrate. Possibly too much nutrients would be released too quickly? I assume they'd have a much higher nutrient content than a standard potting mix.
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post #5 of 13 (permalink) Old 12-06-2015, 07:56 PM
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I used leaf mulch in my veggie garden last fall, just tested out a small area. By the time summer ended, the four inch pile of leaves was effectively soil. Grew garlic super well!

So I put in a four inch layer this fall over the entire veggie garden. Pre-shredded using a leaf blower (mulching option).

Don't honestly know how to make this work in an aquarium other than using the compost as part of the dirt layer during set-up. There's a couple of forum members who used compost for their tanks:

@TheGreenWizard
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post #6 of 13 (permalink) Old 12-06-2015, 08:43 PM Thread Starter
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Originally Posted by kevmo911 View Post
I wonder what would happen if you were to let them dry out and then pulverize them to powder? Would they actually dissolve?

Anyway, I have a Geobin that I'm using exclusively for leaf composting this year for my raised beds. I suck them up and bag them with a lawnmower, which shreds them pretty nicely (though I've considered using a mulching blade to further reduce the size - maybe next year), and dump them in the bin. It would go faster If I turned the pile from time to time, but I'm lazy. As it is, I check with a pitchfork every once in a while, and the further down I dig, the more "dirt" I see. It won't do too much for the next several months unless I mix it up and add air and water (the inside of the pile will never freeze solid in this zone). It should make some really nice compost for the spring.

I have it next to another bin where I dump grass clippings, woodchips, garden waste, and kitchen scraps. Come spring, I'll compare.

Anyway, I wonder what the difference would be if you composted them before adding to the substrate. Possibly too much nutrients would be released too quickly? I assume they'd have a much higher nutrient content than a standard potting mix.
Pulverizing makes me think. I imagine that would make an interesting experiment. If you powdered up the leaves, and dumped it into a tank, I wonder how much of a mess, and how much your plants would benefit. Highly concentrated leaf nutrient? Would it dissolve and make the water brown? So many questions, so little time.
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post #7 of 13 (permalink) Old 12-06-2015, 10:36 PM
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A proper compost pile needs a balance of carbon and nitrogen. I suspect the blended compost with kitchen scraps, green (lawn) clippings mixed with dry or brown (leaves etc) will compost a lot better than a pile that is pretty much pure carbon (leaves only) with just a trace of nitrogen. Toss some lawn fertilizer on the leaves, or water them with used aquarium water. See the article listed in the first post. See the comments about agricultural land needing nitrogen when leaves are used as soil amendment? The decomposer organisms need nitrogen to decompose the leaves. If there is not any in the leaves (and there is very little in fallen leaves) then these organisms will get it from the surrounding soil, depleting the soil reserves. In an aquarium there is usually nitrogen (protein in fish food supplies it). In a compost pile there is not source of N unless you add it, and blend it well with the brown leaves.

Chopping the leaves for any purpose (aquarium, compost or direct garden use) makes a lot more surface area for the decomposer organisms to latch onto, so the leaves will compost a lot faster as long as the other needs of these organisms are met (oxygen, nitrogen). Whatever is in the leaves, released by the microorganisms will enter the water faster, in greater amounts. Garden: burst of nutrients. Compost: Faster composting. Aquarium: high tannin level, high nutrients, but it won't last long.
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post #8 of 13 (permalink) Old 12-09-2015, 01:22 PM
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If you put leaves in a sump to let them break down over time, would that actually release carbon in a useful form for plants?
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post #9 of 13 (permalink) Old 12-09-2015, 03:17 PM Thread Starter
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If you put leaves in a sump to let them break down over time, would that actually release carbon in a useful form for plants?
I think it would. But, why wouldn't carbon like you put in your filter do the same? Are carbon 'rocks' to tough to break down in the tank? Leaves break down readily in my tanks. I never take them out, they just dissolve over months. Interesting thoughts. I'll start another thread on filter carbon and see what happens.
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post #10 of 13 (permalink) Old 12-09-2015, 10:57 PM
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Have you ever known the carbon to dissolve in water filters? I haven't. You have to replace carbon because it clogs up and stops filtering. That tells me that it would not be a good source of carbon for aquatic plants.

Plants evolved to get carbon from CO2. Some aquatic plants can get carbon from liquid carbon sources such as Seachem Flourish Excel. However, plants must produce an enzyme that breaks it down. Not all plants can produce this enzyme. Those that can produce it only do so when CO2 is scarce and the liquid carbon is available on a regular basis. It takes them awhile to gear up to producing the enzyme. CO2 is a far more efficient source of carbon for plants. Aquarists wouldn't bother with expensive pressurized CO2 systems if putting a bag of charcoal in a filter did the trick.
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post #11 of 13 (permalink) Old 12-09-2015, 11:14 PM
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Originally Posted by Argus View Post
Have you ever known the carbon to dissolve in water filters? I haven't. You have to replace carbon because it clogs up and stops filtering. That tells me that it would not be a good source of carbon for aquatic plants.

Plants evolved to get carbon from CO2. Some aquatic plants can get carbon from liquid carbon sources such as Seachem Flourish Excel. However, plants must produce an enzyme that breaks it down. Not all plants can produce this enzyme. Those that can produce it only do so when CO2 is scarce and the liquid carbon is available on a regular basis. It takes them awhile to gear up to producing the enzyme. CO2 is a far more efficient source of carbon for plants. Aquarists wouldn't bother with expensive pressurized CO2 systems if putting a bag of charcoal in a filter did the trick.
We're not talking about high amounts of carbon here. But most lakes and streams, worldwide, have something like 2-3 times the CO2 concentration of the atmosphere. I think decaying plant matter contributes to that, which is why this thread is mostly about leaves.

But I agree that solid carbon "rocks" wouldn't contribute much, if any, carbon in any form.
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post #12 of 13 (permalink) Old 12-09-2015, 11:31 PM
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Originally Posted by kevmo911 View Post
We're not talking about high amounts of carbon here. But most lakes and streams, worldwide, have something like 2-3 times the CO2 concentration of the atmosphere. I think decaying plant matter contributes to that, which is why this thread is mostly about leaves.
It is the bacteria eating the leaves that produces the CO2. I think you would need a lot of leaves and bacteria to get anywhere close to what pressurized CO2 will give you.
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post #13 of 13 (permalink) Old 12-09-2015, 11:33 PM
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It is the bacteria eating the leaves that produces the CO2. I think you would need a lot of leaves and bacteria to get anywhere close to what pressurized CO2 will give you.
Again, nobody's talking about CO2 levels that approach something like those you'd get from pressurized. But I'll tune in to the other thread.
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