permaculture

["John D'hondt" <dhondt@eircom.net>]

We only see algae growing in highly "fertile" waters. Especially if they 
contain runoff from chemical Phosphate fertilizers.
john

> Thanks Lawrence,
>
> The shading from plants may reduce evaporation but that is probably more 
> than offset by transpiration via the leaves.
>
> I hit on the idea of trying to encourage algae growth in my irrigation 
> system because of something I read about high fertility in some of the 
> ancient cultures in which irrigation was used.  It was assumed that part 
> of the fertility was due to the algae that would form in the extended 
> network of irrigation channels.
>
> Dieter
>
>
> --- On Sat, 11/19/11, Lawrence F. London, Jr. <venaurafarm@bellsouth.net> 
> wrote:
>
> > From: Lawrence F. London, Jr. <venaurafarm@bellsouth.net>
> > Subject: Re: [permaculture] Growing algae in irrigation water?
> > To: "permaculture" <permaculture@lists.ibiblio.org>
> > Date: Saturday, November 19, 2011, 1:06 PM
> > On 11/19/2011 5:14 AM, Dieter Brand
> > wrote:
> > > Hi, I have a request which may be a little strange and
> > perhaps there
> > > is no real answer to it. Anyways, it does occupy
> > my mind:
> > >
> > > I live in a semi-arid region with a prolonged and
> > severe dry season.
> > > So, every drop of water I can save counts. I
> > have a spring up in the
> > > mountain and several water holes which together
> > provide just enough
> > > water to irrigate about half an acre during the dry
> > season, if I use
> > > it very sparingly.
> > >
> > > I recently hit on the idea of letting the irrigation
> > water run
> > > through open channels or a series of containers where,
> > under the
> > > light of day, algae would form in the water. I
> > do believe that these
> > > algae would have a beneficial effect on the irrigated
> > soil.
> > >
> > > The problem is that I don’t want to expose the water
> > directly to the
> > > sun since I don’t want to risk that any of it
> > evaporates. What would
> > > be the best way to construct such waterways?
> > Should I cover them
> > > with some sort of semi-transparent shading cloth that
> > is permeable to
> > > air? Or should I use transparent glass or
> > plastic that isn’t
> > > permeable to air? I don’t want the water to
> > heat up under the glass
> > > or plastic. But if I use a shading cloth, I’m
> > not sure that none of
> > > it will evaporate. As I said, I can’t afford
> > to loose a single
> > > drop.
> >
> > Shade it to keep it from heating up and put plastic over it
> > to prevent
> > evaporation
> >
> > alternate: run the water into a small pool or pools,
> > containers, ponds
> > where you have many aquatic plants growing including
> > duckweed which will
> > completely cover the water surface, shading it and
> > preventing much
> > evaporation - you will get nutrients from the decaying
> > plant material -
> > you might get algae growing too but it will need nutrients
> > to survive
> > and the duckweed will also feed on those nutrients and
> > outcompete the
> > algae to dominate the water surface - introduce fish,
> > snails and other
> > organisms that thrive and coexist with other inhabitants of
> > a freshwater
> > environment. As for quality of plant nutrients in the
> > output of the
> > impoundment this may be better than water from algae
> > culture.
> >
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