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Why place crop trees so close to or on a swale?  RSS feed

 
Bret Glassett
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Location: Grass Valley, CA
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Hey All,

It seems so many permaculture cross section drawings of planted swales include crop trees on or right at the toe of the berm. I small for planting no maintenance plants and shorter crops like fave beans on swales or at the toe.

However  - In my experience placing the trees here makes them hard to fence, maintain, access with ladders etc on a swale that is less than say 8' wide. Swale maintenance also becomes more difficult. So I tend to plant the trees below the swale according to the recommend spacing per the tree size.

Is there something I am missing? Is there some advantage to planting on or at the toe of smaller swales?
 
Marco Banks
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Location: Los Angeles, CA
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You plant on the downhill side of the swale (below the l berm, right where it meets the original slope of the hillside) because that is where the "lens" of water will slowly percolate and infiltrate the soil profile.  Water tends to move parallel with the original slope of the hillside, so any water that collects in the swale will move down toward your tree roots below.  Its easy enough to picture it running along the top of the soil, down the hillside.  In the same way the water "runs" down the hill, but below the surface.

Inside the concave of the swale (the bottom) and on the convex berm (the top of the hump) plant ground-cover plants, preferably nitrogen fixing.  These will accumulate biomass and fertility (particularly down in the bottom of the swale).  That fertility will be carried with the water as it moves past the root mass of your trees.
 
wayne fajkus
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I'd say your thought is held by many. No trees on top cause 0f the settling that may occur.

 
Matthew Lewis
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Location: Canada
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Thanks for bringing this up Bret and for your insights Marco.

I've had the same thoughts myself. Also noticed that many Swales have trees right on top but I've always thought that would make harvesting difficult if it were done on a large scale.
 
Bret Glassett
Posts: 14
Location: Grass Valley, CA
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Marco Banks wrote:You plant on the downhill side of the swale (below the l berm, right where it meets the original slope of the hillside) because that is where the "lens" of water will slowly percolate and infiltrate the soil profile.  Water tends to move parallel with the original slope of the hillside, so any water that collects in the swale will move down toward your tree roots below.  Its easy enough to picture it running along the top of the soil, down the hillside.  In the same way the water "runs" down the hill, but below the surface.

Inside the concave of the swale (the bottom) and on the convex berm (the top of the hump) plant ground-cover plants, preferably nitrogen fixing.  These will accumulate biomass and fertility (particularly down in the bottom of the swale).  That fertility will be carried with the water as it moves past the root mass of your trees.


In my experience the lens of water tends to be from the toe of the berm down about 30' on the hillside - dependent on slope, soil and amount of water. Therefore planting directly at the toe of the swale, from what I have seen is not necessary as you can move the tree downhill and still achieve the desired soil moisture benefits for the tree and reduce the access issues with the tree on the swale berm toe. But again, asking because I am not sure if someone out there has experience loving their fruit trees on or at the toe of the swale.

Thanks all!
 
Jane Reed
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Location: Fair Play, Northetn California
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I'm very glad to see this topic, as I planted 2 seedlings atop a recently dug swale and am now concerned that their roots may rot. There's been 50-plus inches of rain this season (unusual for this area) and the swale has been full of water for many weeks.   Additionally, everything outside my fence must be protected from deer and that is awkward on the small berm.  In future, trees or shrubs will go below the berm.
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