Water Landscapes and Clay Soils

Hi,

I was at the Montana Sepp Holzer workshop last year and we talked a lot about healing land that is headed towards desertification. In "Desert or Paradise" Sepp talks about creating water landscapes by connecting a dam to the natural impermeable layer deep under ground. His examples are predominantly (all?) coarser soils. What happens when the impermeable layer is just (1 foot) below the surface? I created a small pond last spring during a dry spell, and as I dug the deep zone I pulled out first a thin layer of hummus, then dry clay, then a layer of wet clay, then more dry clay. The water is actually trapped in the ground between layers of clay. My understanding is that with clay soils the major need is to build organic matter - tap roots, mulching, rotational grazing, hugel beds, etc. How do water landscapes apply in situations where the soil permeability is really, really low?


Thanks!

--
Karen

Hi Karen,

I am wondering.. in your example, how much water do you get per year?

It seems to me that standing water, like a pond, would have time to soak through all of the clay layers?

Did you fill the pond yet ? Does it loose level ?

Adding deep rooted plants would dig channels through the layers also.

Miles Flansburg wrote:
It seems to me that standing water, like a pond, would have time to soak through all of the clay layers?

Not if it is naturally impermeable. Natural pond liner--could be expansive clay, could be compacted. We have it, too.

Ah, good call R Scott!

So the cure seems to be roots?

I live in Vermont. We get 33.6 inches of precipitation per year on average. The driest month is January with an average of 1.86" (usually frozen). May - September all average over 3" per month. On occasion we get 3" in a day.

In general, the clay seems pretty compacted. Some of it looks like it would be right at home in a pottery studio, although most if it isn't that bad. If I dig a gentle, shallow hole with a shovel, water will infiltrate eventually, but if I dig any holes with a machine the water won't infiltrate, or will infiltrate so slowly as to be unnoticeable. Our first year we had a couple test holes dug for the wastewater system. They filled with rainwater and did not drain. We were able to water some new fruit trees during a weeks-long dry spell with water from these holes.

The pond filled with water quickly during one week in June (we got almost 10" of rain in June last year). It is at the bottom of a sloping field. The water level fluctuates slightly, but it actually stayed pretty full even through about four weeks with very little rain last summer.

My question doesn't just apply to my site - I would like to discuss the question in general - can or how can water landscapes help rejuvenate areas with heavy, low - permeability soils. In my area, we usually get rain evenly distributed throughout the growing season. The challenge is that with low-permeability soils the top layer gets very soggy, but the water doesn't penetrate deep into the soil for long-term water storage. In a drier climate, or a climate with seasonal rainfall and heavy soils, the problems are exacerbated. Maybe there aren't very many of these locations in the world because these areas are more prone to loss of vegetation and erosion, so the fine clay and silt particles get washed away, leaving the more sandy soils that Sepp widely discusses.

Thanks for the comments!

Miles Flansburg wrote:Ah, good call R Scott!

So the cure seems to be roots?

Roots that penetrate and die back, like daikon. Just planting a tree won't do it, the clay seals back around the roots--unless it is a chop and drop tree.

Or key line plowing if you can get deep enough. Even if you can't get through the clay layer, the plowing will move the issue from 4" down to 24" which is a huge deal IMO.

My current property has this blessing/curse. I learned to deal with it and am starting to learn how to take advantage of it.

We have something similar here. Except, that we are very close to bedrock. So we have two almost impermeable layers on top of each other. That's it, no other "soil".
I have been giving it some thought and I have come to the conclusion, that the only real strategy is to build soil on top. And yes, tap roots help.
This fall (if we have the time) we are going to try some different techniques, to see which one works best on our land. Managed grazing, massive mulching, green mulching and combinations of these.
Any other suggestions are welcome.

Marcus - there is no "except" I have the same thing - bedrock anywhere from on the surface to maybe 10' deep.

Any thoughts on water landscapes? Can and how can water landscapes help in regions with very heavy soils?

I also have bedrock from zero to 10 feet. One thing I realized is the bedrock contour is DIFFERENT than the surface contour. Once you get an idea of where it goes, you can sometimes use that to push water uphill to feed the trees.

What a good idea - how do you find the bedrock contours?

Karen, the clay should be able to hold some ponds, so I have considered make a lot of them. I don't know if they will help with the general clay problem but it's a way of turning a problem into a solution.

Hey Karen, without knowing much about your site but knowing a bit about Vermont history it sounds to me like you are seeing the effects from when they tried to turn Vermont into Scotland. At one point nearly the entire state was cut and turned into sheep pasture. My guess would be that the second impermeable layer your are finding (underneath the wet clay) is the "natural" impermeable layer, and the first layer of hard compacted clay is the result of poorly managed animal grazing. If I were in your shoes I would build water retention structures tied into this second impermeable layer. Key line plowing through this first hard layer seems like a good potential strategy to relieve some of the compaction and increase infiltration. Certainly plant roots do a great job of this as well. Water landscapes also do a good job of this, as clay saturates with water it's structure also loosens. If your think of the clayey soils in wetlands they are never very compacted because the structure of clay is loose when full of water.

Karen Walk wrote:how can water landscapes help rejuvenate areas with heavy, low - permeability soils.

Water landscapes are very easy to build in heavy clay soils, and these soil's are often some of the richest and most nutrient dense you can come across. While clay can be more difficult material to work with it is also the most valuable to have in your soil. Water landscapes relieve the problems that you touched on, with the soil being too saturated in the wet times without enough storage for the dry. By regenerating the veins of a property you create places for the water to go and be stored. As part of this action of reinvigorating the water lines and removing the eroded sediment clogging the waterways you are not only creating wet areas for the dry times but also drier areas for the wet times. The sediment that is removed often becomes part of some type of mound culture, providing plants with drier areas during the wettest times of the year. During the dry times the long term water storage from the retention areas wicks into the surrounding ground, and these mound cultures, providing long term water storage. So water landscapes not only provide benefit to coarser soils in drier climates, but also in heavy soils in more humid climates.

The project that I am just leaving right now in Ecuador is a perfect example. During the wet season people say that you cannot grow any vegetables as they will all be inundated and mold. People actually build greenhouses in this tropical climate, just to protect vegetables from the tropical rains. Yet in the hugelkulturs that were created here as a test a year ago there is beautiful kale and squash, without a speck of powdery mildew, even towards the end of the wet season. The hugelkulturs not only provide moisture during the dry times but also drier soil for more water sensitive plants during the wet season.

Marcus Hoff wrote:What a good idea - how do you find the bedrock contours?

Ground penetrating radar. If you are made of money.

Dig lots of post holes if you are a normal guy like me. and a basement. and septic.

Zach Weiss wrote:My guess would be that the second impermeable layer your are finding (underneath the wet clay) is the "natural" impermeable layer, and the first layer of hard compacted clay is the result of poorly managed animal grazing.

This makes perfect sense! And yes, you are absolutely right. Lake Champlain allowed an easy route for timber to be sold in New York, so after most of Vermont's original forest was denuded, Vermont was completely covered in Sheep pasture. Even after the collapse of the wool industry in Vermont there was still more topsoil loss due to over-grazing of dairy herds and erosion. Ben Falk goes into this much more eloquently and in more detail in a post here:

http://www.wholesystemsdesign.com/rapid-topsoil-formation/

In regards to a water landscape, I think with heavy soils it makes sense to create a network of closely connected ponds or lakes, tied into the deep impermeable layer. I would not concentrate on shallow streams, water meanders or deep swales because with a heavy soil I don't think that this type of construction will greatly increase absorption of water into the soil. The soil is just too dense. I think that key-line plowing would be more effective. Ponds have two major benefits for the surrounding landscape in terms of soil quality:

1. The greater water depth in a pond will create some pressure to help water infiltrate into the surrounding soil. Over time this will help loosen soil.
2. The act of digging the pond provides material that can be used to create high spots. The high spots will (eventually) be hydraulically connected to the pond, allowing water to be wicked into the soil, without creating an anaerobic environment.

Obviously, ponds have many other benefits in and of themselves.

In addition, you need to convert the heavy top layer of low-organic matter soil into high-organic matter, highly fertile soil. Here are some strategies that I think make sense:

*Key-line plowing and seeding of beneficial plants into the key-line. Seems like this can be effective for large areas.
*rotational grazing - ruminants followed by birds, ideally - coupled with key-line, this could make a major difference
*compost tea - increase the microbial life in the soil
*mulch - I'll be using mostly woody mulch, and probably inoculate it with beneficial mycellium
*deep rooted plants - specifically taproots - plant them and leave them in the ground!
*hugelkultur for intensive growing beds

Last year I created some sod-cutter swales - basically flipped about four layers of sod into a small area to create a mini swale. Trees, bushes and cover crops were then planted into the open soil. The mini swales did catch and help infiltrate water. The idea was that we were catching water with something permeable, so slowing the water down, but not permanently catching it behind an impermeable barrier. While walking around in the snow last week I noticed that in this area there is MUCH more animal activity than in the open fields. Lots of small animal tracks, and lots of fox tracks and coyote tracks. There were also more fox/coyote head holes. More life!

Hi all,

I'm in south central washington on the SE foothills of Mt. adams. We have shallow heavy clay soil (easily compacted), and only a few inches (at most) of accumulated top soil. In some areas bedrock is exposed, and on the hill tops and in some detritus slopes soil can be upwards of 12-feet deep. (we have done some exploratory digging)

We get ~25" of precip a year. most of which is snow. A dry season of 6 months from May-June to Nov-Dec.

We are using a combination of:
-terraces (everything is sloped here) ,
-small swales/access roads (to trap water, leaf material, provide foot and car access, and to establish contour hedgerows),
-water retention basins (basically unsealed ponds),
-hugelkultur to build deep soil biomass quickly,
-deeproot pioneering pasture plants that are chop-and-drop. (alfalfa, perennial bunch grass, comfrey, chicory, salsify, etc)
-fast growing annual/biennial roots (turnips, rutabagas, Mullein, curlydock)

In more open areas we are currently implementing perennial dryland pasture, with a keyline design and a contour swale forage hedgerows and cell grazing. We believe this will work well in our conditions, and provide us with the animal forage we need for our goats and sheep.

We are not building "ponds", in the sense that the intention is to hold water above the soil surface. But we have all of these water retention strategies working together to get water to stop and infiltrate. We have areas to collect and hold water when we have it, but these are not sealed. because we are in a highly evaporative landscape for half the year, we are working mostly to hold water in the soil.

Hi Andrew,

It sounds like you are creating ponds in a similar way to Sepp Holzer. His ponds are never sealed in the traditional sense. Basically he builds a vertical barrier in the earth that connects to a natural deep impermeable layer and allows the water to build up on the earth on the uphill side of the barrier. The idea is to re-hydrate the soil. The pond is almost secondary.

How is they keyline working for you? I have lots of compacted pasture and am planning to start with keyline this spring.

Thanks!

--
Karen

Karen Walk wrote:Hi Andrew,

How is they keyline working for you? I have lots of compacted pasture and am planning to start with keyline this spring.

All of the subsoiling I have done has had good results, but we have not done any largescale keyline plowing yet. still trying to find some kind of subsoiler that works with the equipment we have.

Up until this point, I have used a self propelled rototiller type thing with the tillers removed and a single "tine" on it. It has obvious effects on plant growth and water infiltration. I am looking forward to scaling it up in our pasture. That will probably have to wait until the fall or next spring since I have yet to find something that we can work with.

Andrew:

What do you have to work with?

Andrew:

What do you have to work with?

Your tiller mod sounds like a good option for small spaces. For the larger areas check out open source ecology. I know that someone over there was working on a keyline plow. I'm lucky in that someone in the area has a good keyline plow, and knows how to use it!

R Scott wrote:Andrew:

What do you have to work with?

as far as tractor: We have a furgason TE20 farm tractor (or the equivalent, not sure the exact model). It is a standard " Little Grey Fergie" and has the common tree point implement linkage.

http://en.wikipedia.org/wiki/Ferguson_TE20

Karen Walk wrote:
Your tiller mod sounds like a good option for small spaces. For the larger areas check out open source ecology. I know that someone over there was working on a keyline plow. I'm lucky in that someone in the area has a good keyline plow, and knows how to use it!

I have looked at OSE. There keyline plow, at least what I saw, looks like it doesn't work too well. and it has little of the precision and capacity to big rigged for variable depth and spacing.

here is a video:
http://blog.opensourceecology.org/2012/10/more-machines/

It also appears to bring a lot of subsoil up to the surface, and their model has only a single depth. perhaps others have arguments for why this is a credible alternative to a yeoman style plow? I am not seeing it.

http://www.tractorsupply.com/en/store/countylinereg%3B-sub-soiler?cm_vc=-10005

I have a little john deere compact utility, probably less pulling power. I took an angle grinder to knife the front edge as Darrin Doherty suggested and I can pull it through pretty compacted clay.

Andrew - the idea behind OSE is that equipment is home - made, home - repairable and inexpensive. If it were your thing you could modify the design to allow additional functionality. At some point it makes sense to buy a yeoman plow.