Topsoil from Ponds

Ozark, MO(Zone 6a)

A big silted-up farm pond near us has been going dry for years, and it dried up completely this summer. Today I saw it's being dug out by a bulldozer and a front-loader, and big piles of gray-black silt are being piled up in that pasture. I mentioned to someone that they're fixing that pond, and found that the main reason it's being dug out is for topsoil. They may also pack it down with dozer treads and get the pond to hold water again - maybe.

Rock-free topsoil is a valuable commodity here, as the Ozarks don't really have rocky dirt, it's more like we have dirty rocks! Topsoil has to be hauled in for new lawns and gardens. The fellow told me that old silted-up ponds (and some of them are over 100 years old) are often "mined" for rock-free topsoil - but the soil will kill plants and won't grow anything for several years after it's dug out. The pond silt has to be piled and "the air has to get to it" for several years, and then it becomes good rock-free garden soil.

I've been thinking about it, and I'm not sure what's going on with that. This is silt that has been waterlogged for decades, but why would it be toxic to plants at first and then lose that toxicity? Any ideas?

Everett, WA(Zone 8a)

Hust guesses:
- something like salt or acids need to be flushed out
- oxygen needs to let in so the soil population can change over from anerobic to aerobic
- accumulated organics "aren't right" in one way or another, probably because the pond bottom was anearobic
- the structure of silt is too fine and won't drain or aerate

Variations on those themes:

Anerobic fermentation in the silt turned organic matter into acids or other fermentation products toxic to root hairs.

Anerobic conditions slowed down the digestion of organics so much that they built up to the point where they would suck oxygen away from the roots, or prevent beneficial microbes from growing

Accumulated organics have too much carbon, and a nitrogen deficeit.

Some other nutrient is present in excess.

Salted up? If salty dust blows in, and water evaporates instead of draining, I could imagine salt accumulating. Aluuminum is very toxic.

Just plain unfriendly anerobic microbes are present in such numbers that they crowd out plant-friendly aerobic microbes?

The silt is too dense with fine particles, and won't drain or aerate until some of the fines wash out, or the silt is churned up enough (by worms and bugs and frost?) to create clods, clumps, "peds" and channels for airspace to be created.

Ozark, MO(Zone 6a)

Good thoughts, all of those.

This is hardwood forest country, and I think it's leaves that "silt" ponds up over the years. There are so many trees (mostly oaks) that even ponds far away from trees get a lot of leaves in the fall as the wind blows. Those fill and choke a pond in time. Like you, I think whatever goes on with all that organic material in an anaerobic environment wouldn't produce good soil. All the tannin from those oak leaves probably has an effect too.

Everett, WA(Zone 8a)

Oh, yeah! Acid and tannin. Yuck!

Anne Arundel,, MD(Zone 7b)

What he said.

Everett, WA(Zone 8a)

One friend had a scheme with oak leaves. He would pack what he raked into big plastic bags and just store them dry for a year, "letting the tannin break down".

Then he would compost them. I don't really know how much that helped, but it worked OK for him.

It would make sense to me to shred them first, so they could be stored in a smaller space, and let them be wet and attract worms for the whole first year - basically make it a two-year composting. Maybe even lime them just a little the first year. But I don't have experience with oak leaves.


Virginia Beach, VA



Ozark, MO(Zone 6a)

Every year I chop up oak leaves with my riding lawnmower and add them to my compost piles. Mixed with green grass clippings, they soon break down into good compost.

By themselves, though, I don't believe oak leaves help the soil. I own some property for deer hunting in the next county and I've often sat under a tree there in the deep woods waiting for a deer to come by (I'll be doing that next week). Every fall those woods get a thick layer of oak leaves on the ground, and they pack down in time and make what appears to be good black soil.

Scratch in that soil with your finger, though, and it's only about an inch deep - after centuries of leaves falling and decomposing. Underneath there's just rocks and poor clay, and the thin layer of decomposed leaves doesn't seem to grow anything. Instead, it acts as a mulch and keeps small plants like grass and weeds from growing.

Anne Arundel,, MD(Zone 7b)

Oak leaves seem incredibly hard to rot to me. I don't quite see how dry bagged leaves are going to get any encouragement to break down over ones exposed to sun, air and rain.
(Anyone care to set up a long term experiment? )
I got beaucoup bags of shredded oak from a neighbor last year . Used them over some months, used some right away as mulch . The bottom of the bags would rot some where water collected but the top would be just as fresh as the day they went in.
I can't really say as I have only one tree so those get mixed with other leaves. I think chopping is a must with oak leaves.

but seems to me ; ^) that why didn't he just build bigger compost heaps and add more nitrogen at the get go. Or expose them to ground and rain. (Rain brings some nitrogen) The only help I see with bags is getting them to stay moist.

Anne Arundel,, MD(Zone 7b)

Good field observation, Ozark.

Everett, WA(Zone 8a)

I would agree with you: if you're going to store them, store them wet and exposed to worms.

I recall that he was big on "minimum effort". He certainly wouldn't risk having to rake them twice if they blew around! Maybe he thought that tannin would inhibit other things breaking down?

Anyway, if I ever get access to lots of oak leaves, I'll give them their own compost heap with enough N to help them break down if they're willing. Then add them tothe main heap, or use them, after I guess that the tannin and acid have mellowed out.

Anne Arundel,, MD(Zone 7b)

Sorry if anybody minds the straying from pond dirt-

To me max breakdown for minimum effort is rake into a pile and cover with a tarp. They get moist and warm , and worms, from the ground up.

I could talk about rottten leaves all day.....

Bardstown, KY(Zone 6a)

Sally how'd the Eastern Wahoo do this year?


Charlotte, NC(Zone 7b)

I believe Rick is correct regarding the pond silt.

As to leaves - we have literally gathered hundreds of bags of them from all over the neighorhood during the past five years. No doubt many have been from oak trees (including our own oak tree.) Earthworms break them down into wonderful free dirt, which is then added to the raised beds. I've never experienced adverse effects doing this - although I do add a small amount of dolomite lime to the beds each year.

We have stopped adding dry leaves to the compost bin as they come out just as dry as when they went in!

Everett, WA(Zone 8a)

>> I could talk about rottten leaves all day...

Me, too. Making compost is fun and feels virtuous. Dead plants, manure, kitchen scraps, biosolids ... yumm!

I find that I enjoy digging, turning and "cultivating the soil" more than I enjoy "cultivating plants". When I started re-making my yard, I was THRILLED about trenching, making raised beds and amending soil ... then tried to think of something I wanted to PLANT in that new soil.

Fortunately, between being attracted to some flowers, and stubburn about getting others to live, and finding a few vegetables that I liked if they were fresh enough, I now have plenty of "excuses" to make more beds.

Enough so that I would still run out of bed space even if I had three times as much.


rhinelander, WI(Zone 4a)

leaf mold is added to bonsai soil and I had heard of a method of gathering oak and maple leaves in a garbage
bag -- in a year you can add it to your soil mix ? Sounds like it would not be broken down in a year ?

rhinelander, WI(Zone 4a)

Our pond had dried up too and muck should make good soil -- but it needs to compost first ?

Anne Arundel,, MD(Zone 7b)

Just "putting leaves in a bag'- is not likely to have them well broken down in a year. They need at least to be mopiost and have some nitrogen with them. Prepped and bagged- you will probbly have some usable stuff and some still not borken odwn. Turning the bag would help.

The pond muck- might be a good addition to leaves. Probably should use it as an "amendment" in case it is too high in some aspect ( density, some breakdown chemicals)

Doug- grew somewhat, I'm looking forward to future years. I was just about to look up fall color and decide whether to move it while still young. Thanks again. Is sweetshrub OK?

Anne Arundel,, MD(Zone 7b)

well duh, I have from the library right now, William Cullina's Native Trees Shrubs and Vines, and Dirr Hardy Trees and Shrubs...all I could want to know about Wahoo ought to be covered)

rhinelander, WI(Zone 4a)

thanks sallyg and corey , likewise aquarium water would be too strong for plants , and would need to be diluted.
i.e. thought of a good use for used aquarium water when doing water changes of fish tank? thanks ozark for starting
thread , George Washington Carver talks about using natural fertilizers instead of synthetic ones.

Anne Arundel,, MD(Zone 7b)

I don't have anything to back this up but I assume that my aquarium gravel rinse water is ok for plants as is. Freshwater tank of course. There may be a previous thread on that question.

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