[Pil-pc-oceania] swale building

[RussGrayson]

Hi Ian...
Just a follow-on to support what you say and something about terms as
well...

On 21/11/07 11:56 AM, "ian lillington" <ian at masg.org.au> wrote:
Thanks Sue 
> 
> In dry central Vic., if the tree is already established, I dig a shallow dish
> by hand around each individual tree.  That means that when I have one or two
> buckets of water, I can easily pour it into the dish and be sure that it
> infiltrates in the right place .

This is what I understand to be a micro-catchment, a term that also
describes swales. On sloping land, a ditch can be cut on the upslope side of
a tree and the spoil used to form a small bund to dam runoff on the
downslope side.

Ditching around a tree is an idea we teach in Randwick Council's Sustainable
Kithen Garden course for the sandy soils of Sydney's Eastern Suburbs.

> At mid scale, I have seen swales laid out with old tyres and newspaper
> bundles, or stones, or brush from fallen trees; cut slightly into the ground
> (let's not have the old tyre debate here).  anything that stops the water
> moving too fast down hill is worth while.

This is what I call 'bunding' because the type of structure Ian desribes is
technically known as a 'bund'.

A bund is a water retaining structure above ground level. Commonly, in
places like dryland Africa, it is constructed along the contour, as are
swales, with the purpose of increasing infiltration for crops.

A LIVING BUND
I once did a story for a magazine on Regenesis Farm in Northern NSW. The
managers call what they do 'systems farming' (as in systems theory or
systems dynamics) but most of us reading this would recognise the place as
the application of permaculture design principles at a commercial scale.

Regenesis, at that time, had an installation I immediately recognised from
what I have seen from a project I worked with in the Solomon Islands. There,
they call it 'alley cropping' and it consists of linear cropping strips
between alleys of mainly leguminous crops. Although the leguminous trees
(Gliricidia, in the Solomons) can grow into trees, they are kept to a low
height because they are slashed and their foliage thrown into the cropping
alleys as a nitrogenous fertiliser.

At Regenesis, pigeon pea (Cajanus cajan) and other small trees occupied the
tree alleys, along with crops such as pawpaw. But to get to your point, Ian,
where the cropping alleys are usually free of earthworks, those at Regenesis
were occupied by bales of hay (grown on the farm) and placed along the
contour. Atop them, compost had been placed and seeds/seedlings established
into this. It was a living bund.

I suppose you could think of the installation as a vegetable garden raised
atop a bund of bailed hay. As the hay broke down it added nutrients to the
soil and, as it was grown and bailed onsite, energy input was minimal as
transportation was minimised. It also had the benefit of retaining nutrients
onsite rather than importing them from offsite, ie. bringing in someone
elses' nutrients. This is just one reason Regenesis is a 'systems farm'.

You can read about Regenises at:
www.pacific-edge.info/journalism/food/regenesis.html

DITCH AND MOUND
You can see that a swale can be constructed as a ditch with the spoil from
the excavation of the ditch placed as a bund on the immediate downslope
side. I mentioned in an earlier email to Sue Mossman today, that civil
engineers sometimes describe swales as 'contour ditches'. So, too, is the
swale and mound sometimes called a 'ditch and mound' system.

That term also describes artificial wetland agricultural structures
(sometimes, agro/piscicultural systems - ie. crops on the mounds and fish in
the excavated and flooded troughs) in which excavated fill from parallel
ditches forms the linear mounds between them and the ditches are flooded.
Found in Vietnam, ancient Mexico and elsewhere (Aztec structures called
'chinampa').

There was such a structure at the Permaculture Research Institute when it
was at Tyalgum, NSW. I visited it on a number of occasions. Once, it had an
algal bloom. At one stage, flowers, presumably for the cut flower market,
had been started on one of the bunds and, at another time, chickens were
being kept there. I never saw the bunds under intensive agrucultural
production and I do not recall whether the managers stocked the ditches with
fresh water fish. 

You can see an image of the structure at:
www.pacific-edge.info/journalism/travel/pri.html

Those above are just terms we might come across.
 
> On a larger scale - yes, heavy plant is a marvelous thing when used in the
> right way. Since 1992, I have been teaching that it makes sense to save our
> oil for jobs such as this.

I think, Ian, it's like your earlier email today said about cheap
international air fares - these, like oil for heavy plant, are opportunities
we can use (while they are there) to spread our message.

My unerstanding is that it is about EROI - Energy Return On Investment, with
'energy' in your case, Ian, being measued as agricultural productivity.

It could just as easily be estimated in intellectual terms as an increase in
knowledge or the acquisition of useful information as the 'energy' output.
In this measure, the return on investment might come some time after the
acquisiton of knowledge or information as that might not be applied for some
time.

The point is whether the eventual outputs/outcomes are equal to or exceed
those of the fossil fuels spent in their acquisition.

We can only try.

...Russ

> 
> Interested in both comments
> 
>  
> 
> Firstly that it is not hard to build a swale - and suggest it is hard, without
> major
> plant.  Which brings a second issue, what will we do when peak oil hits and we
> cant use
> heavy plant??
> 
>  
> 
> Then there is the issue, that I would prefer a person to make my swales to
> have a PDC
> and at least know the reason and process.  So don't suppose Mathew is in
> Sydney - I need
> some swales.  If Mathew isnt, then is there someone here???
> 
>  
> 
> How will I find out?
> 
>  
> 
> Sue Mossman
> 
>  
> 
> _______________________________________________
> Pil-pc-oceania mailing list
> Pil-pc-oceania at lists.permacultureinternational.org
> http://jasper.cmsarchitects.com/mailman/listinfo/pil-pc-oceania