[Pil-pc-oceania] Pil-pc-oceania Digest, Vol 9, Issue 42

[Robyn Francis]

> Date: Mon, 16 Jul 2007 01:31:29 +0000
> From: "tamara griffiths" <scarletwoman at hotmail.com>
> Subject: [Pil-pc-oceania] Temperate Chinampas

> I am designing some chinampas at my place in Bunyip - Temperate, average
> rainfall 800mm - 1200mm last year, 600mm.
> I am thinking blueberries, cranberries (as an edge plant), and perhaps
> yabbies in the water.
> Water and land about 1.5 wide. Path down the middle of the land to access
> blueberries etc.
> Running north - south.

Hi Tamara
What's your temperature range (I've no idea where Bunyip is), soil-type and
do you have serious water-logging issues?

Chinampas and similar systems are specifically wetland or floodplain systems
where high water tables, permanent and seasonal seasonal swamps,
waterlogging and low level flooding occur. Working chinampas are usually 10m
wide (channels as well as planting bunds) and usually at least 30m long. The
width for the water body is critical to have sufficient depth (1.5-2m) as
well as surface area to support aquatic life. Traditionally aligned around
18deg East of North (lined up with where Pleaides rises at, I think, the
summer solstice).

I've seen a number of failed chinampa-style experiments, mainly due to
imposing the system on an inappropriate site (i.e. not a wetland/swamp) and
trying to down-scale them to something too small to work, especially on the
aqua-production side. Unless there's a naturally high water table, the
channels will be dry for most of the year, even with a heavy clay soil.

Floodplain systems I saw in India had 10m wide bunds for fruit production
and 40m wide paddies in between to grow rice in the wet season then maize or
sorghum in the dry.

I have a heavy clay soil and where there were serious waterlogging issues I
made 1.5m wide taro paddies (20-30cm deep) between my garden beds, using the
soil from the paddies to raise the beds. Works exceptionally well, the taro
can survive well irrespective of whether the paddy is wet or dry. I also
grow other water vegetables in there in the wet. I would not call it a
chinampa, even though it is based on a similar principle.

Ciao
Robyn

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