a soil curiosity

pnbrownMay 19, 2013

For those of you with some knowledge of geology and soil-formation, a scenario:

I've been starting new gardens at my daughter's new location in central MA. There are large outcroppings of granite, surrounded by some relatively flat areas currently lawn. In one direction these slope gently and end up as swamp, or slough, with shallow very slowly-moving water.

Every place I have investigated is about 6-10 inches of jet black slick silty/clayey topsoil, very damp, with very many small pieces of granite in it, and occasionally large pieces. (the grass grows incredibly lush, a shame not to have a cow). Anyway, the real curiosity is that directly underneath this is sand! Just an immediate change, not gradual. Sand with small stones, and the stones look different from the ones in the topsoil. This explains why the grass is not drowned in what should be a saturated location. There is enough sand underneath to give it drainage. I planted an apple tree last fall as a test, it flowered hugely this spring and looks like it's loving it.

There is no possibility that this is an altered site from what I can see. I am wracking my brain trying to imagine how the glacier created this strange yet possibly marvelous situation.

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nc_crn

It sounds like you have a type of Inceptisol, probably a Paxton series (or similar) given how much of it is in the North-East.

    Bookmark   May 19, 2013 at 8:23PM
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nc_crn

Here's an article on the Paxton series.

http://nesoil.com/images/paxton.htm

I'm not sure of the series, but it sounds like an Inceptisol either way.

    Bookmark   May 19, 2013 at 8:24PM
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pnbrown

It isn't Paxton - I looked it up some months ago and have forgotten the name of the complex. I'll have to look it up again.

As I recall the description doesn't give any insight on how the condition was formed.

    Bookmark   May 19, 2013 at 9:25PM
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pnbrown

It is in the "charlton-hollis rock outcrop complex":

Here is a link that might be useful: good apple land

    Bookmark   May 20, 2013 at 7:21AM
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TXEB(9a)

pnbrown - quit wracking your brain and just enjoy it.

It sounds like you basically have a silt/clay layer on top of coarser sand. Am I reading that right? If so, my SWAG is that since it is wet/swampy you're looking at a natural sedimentation pattern where the denser sand settled out, and as the water was repeatedly disturbed silt and clay remixed and settled on top. It's a repetitive process in the post glacial sedimentation and drainage process. Along with that sedimentation came the OM that was incorporated into the silt/clay layer in ensuing post glacial millennia. That the area is wet / swampy, and it's in a relatively cool climate, probably led to OM accumulation rates faster than decay, so you are blessed.

    Bookmark   May 20, 2013 at 9:06AM
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nil13(z21 L.A., CA (Mt. Washington))

are you certain it hasn't been altered? New England was heavily farmed. They even farmed rocky hilly regions to exhaustion causing massive amounts of erosion. These areas were abandoned long ago and people now think the landscape is natural when it is in fact highly altered with forgotten and buried dams and such still effecting things.

    Bookmark   May 20, 2013 at 11:44AM
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nil13(z21 L.A., CA (Mt. Washington))

After pulling up a topo of MA i think I would need a chain of historic maps proving the land had never been altered in order to believe the land had never been farmed. Farming even got pushed to mountainous insanely marginal land. That doesn't happen without less marginal land getting put into production. The answer to your mystery might lie in a library somewhere.

    Bookmark   May 20, 2013 at 12:23PM
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pnbrown

That sounds about right, TX. We'll know soon if it is good for crops. I failed to put calcium on that area last fall, or spring, though I put down wood ash about six weeks ago. Yesterday I planted sweet corn and set some tomato plants, both with dehydrated chicken manure for fertilizer. i expect the tomatoes to do well but acidity could easily be out of range for corn to do well. I did put calcium and compost in the apple-tree hole. The tree predicts that the crops will not drown, at least.

Nil, if you saw the spot you would agree that it has never been plowed. The flat area is so small that it would not have been worth bringing a team and plow there. It is surrounded by slough, ledge, and steep slope. Certainly it would have been grazed, probably by cattle and sheep. Maybe overgrazed, and maybe trampled when too wet.

    Bookmark   May 20, 2013 at 1:53PM
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TXEB(9a)

From your description it sounds almost like a drain basin. That could add a lot of clay/silt, small gravel, and OM on top what would have been there otherwise via just natural wash. If the area above had been used to pen, hold or keep livestock it could have benefitted from decades of animal fertilization.

    Bookmark   May 20, 2013 at 2:16PM
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pnbrown

It would be hard to know for sure what happened there. It's a suburban area all built in the 60's and 70's. As with any such area in new england, at some point before that it would have been part of some dairy farmer's holdings. It is at the tail end of a very long narrow shelf of land with steep slope on one side and ledge and wetlands on the other. It is the kind of difficult terrain that would have been left alone until better areas were taken.

The great likelihood is that it was forested since the glacier retreated, then was cleared in the late 18th or early 19th century (the township was settled in the early 1700's), and from then until the 1960's was grazed by cattle.

    Bookmark   May 20, 2013 at 2:34PM
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toxcrusadr Clay Soil(Zone 6a - MO)

I know just enough depositional geology to be dangerous, but it does not seem odd to me. Sand from glacial outwash, perhaps a river, then conditions changed, depositing a different mix of material. I'm more used to looking at soil profiles in the Mississippi and Missouri River valleys though.

It does seem odd that you have granite gravel in the top layer along with silt and clay, but no sand. If it was glacial till or outwash, the composition should not be skipping over any size ranges like that. But again, I'm no expert and learn new stuff all the time.

    Bookmark   May 20, 2013 at 3:30PM
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nil13(z21 L.A., CA (Mt. Washington))

It was probably cleared before the middle of the 19th century. After the middle of the 19th century, farmland in MA began to be abandoned and started to return to forest. You are probably right that it never saw a plow though. The best method for clearing forest was established early on and didn't involve plowing, especially on such marginal land. They would fell the trees in the summer. Then in the Spring they would burn the felled trees, clear off what was left and plant in mounds and forget about the crop until harvest in the fall. Of course pasture land is also a possibility, but they would have had to plant european grass varieties to accomodate cattle.

    Bookmark   May 20, 2013 at 11:01PM
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pnbrown

"but they would have had to plant european grass varieties to accomodate cattle."

Is that true? I have read that in the early days cattle (and hogs, of course) foraged in woodland and freshly-cleared woodlands. It was a big cause of tension between settlers and natives and one of the factors leading to King Philip's War. This area I am talking about probably had no european residents at that time, but was surely cleared and used by 1800 or so.

Tox, that was my first thought, the sand underneath seems like it is alluvial or riparian. Then water levels dropped closer to the current levels and perhaps the very fine material was washed in during storms over millennia, and organic build up has been heavy, though the soil is not peat-like.

It is amazing how much soil types and substrates vary in the glacial regions.

    Bookmark   May 21, 2013 at 6:57AM
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TXEB(9a)

Where I lived in eastern MI the soil was broadly categorized as "glacial till". The area was fairly low and flat. We had a lot of county land area caught in 100-year flood plains. Where I lived was well out of the flood plain zone, had sandy loam on top for 18", then below you hit fine gravely stuff. Any OM had been long lost to clear cut deforestation followed by about a hundred years of old-school high till farming. About 10 miles away in the flood plain zones the topsoils had a lot of organic matter and fine gravel mixed in. Both sand and gravel pits dotted the county, often on the land rise just above the lower river basin flood plains.

This post was edited by TXEB on Tue, May 21, 13 at 9:47

    Bookmark   May 21, 2013 at 7:32AM
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toxcrusadr Clay Soil(Zone 6a - MO)

I lived in SE Michigan (Ann Arbor) until I was 10. Dad used to talk about the glaciers and the 'hogbacks' which were glacial moraines usually full of gravel. Our yard, though, was clay. Lots of dirt clods got thrown back and forth by the neighborhood kids in the summer. I wish we had had sandy loam. My dad probably would have used fewer cuss words in the garden. :-]

    Bookmark   May 21, 2013 at 12:29PM
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nil13(z21 L.A., CA (Mt. Washington))

pnbrown, now that I think about it, by that time the european grass varieties had pretty completely naturalized. But yes, the European settlers had problems with their cattle early on because the native grasses were not as nutritious as the European species. They brought in European species and those species colonized the country faster than the humans did.

    Bookmark   May 21, 2013 at 4:47PM
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pnbrown

Interesting segue. I wonder if any grasses native to the new england region have survived.

    Bookmark   May 22, 2013 at 6:40AM
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