permaculture

["Lawrence F. London, Jr." <venaurafarm@bellsouth.net>]

On 11/19/2011 6:18 PM, Dieter Brand wrote:
> Thanks Lawrence,
>
> The shading from plants may reduce evaporation but that is probably
> more than offset by transpiration via the leaves.

Dieter, my impression is that it might be good to look into that 
further, transpiration figures for duckweed as opposed to direct loss 
through evaporation, ratios and comparison with water conservation 
figures for other schemes. Also the duckweed with reduce water 
temperature thus reducing loss through evaporation. Google it.

"reduced evaporation in pond when surface is covered with duckweed"

Duckweed - San Juan Islands Conservation District
www.sanjuanislandscd.org/Information/Articles/assets/Duckweed.pdf
File Format: PDF/Adobe Acrobat - Quick View
surface of a 0.5-hectare pond in less than 50 days. ... It can even 
reduce evaporation loss from a pond. With optimum conditions duckweed 
can grow expo- ...

duckweed (lemnaceae): info fact sheet, photos
www.naturia.per.sg/buloh/plants/duckweed.htm
It floats on the water surface in a bright green layer. ... survives the 
winter by producing buds (called turion) that sink to the bottom of the 
pond. ... nitrates and phosphates), the surface area covered by duckweed 
can double in less than 2 days. ... And by covering the water surface, 
it minimises water loss through evaporation. ...

Lemnaoideae - Wikipedia, the free encyclopedia
en.wikipedia.org/wiki/Lemnaoideae
Some duckweed is introduced into freshwater aquariums and ponds where 
they may spread rapidly. ... of water because a cover of duckweed will 
reduce evaporation of water when compared to the rate of a similar size 
water body with a clear surface. ... Duckweed-covered water edged with 
several bald cypress trees ...

Facts on Duckweed | eHow.com
www.ehow.com › Plant Care
Have you ever looked out at a pond and noticed the surface was covered 
in something ... Duckweed also reduces water evaporation and keeps water 
cool. ...

DUCKWEED - FAO
www.fao.org/ag/againfo/resources/documents/DW/Dw2.htm
A considerable proportion of the world's surface is covered by saline 
waters, ..... low in the pond and splashing to reduce surface 
temperature of the duckweed matt. ..... Duckweed was seeded onto the 
"ponds" so that half the surface area was ...... The only major water 
loss from the system being by evaporation if ...

The Pond Report > Duckweed Control, Lemnoideae Removal ...
www.thepondreport.com/duckweed.shtml
Duckweed is a small delicate plant that drifts on the pond surface, 
filling in ... the duckweed helps reduce evaporation which can be a 
problem in a clear pond ...

> 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.

It sounds like a great idea. If you can grow azolla where you are then 
that would be the aquatic plant of choice for accomplishing 
nitrification of irrigation water.

DUCKWEED: A tiny aquatic plant with enormous potential for agriculture 
and environment
http://www.fao.org/ag/againfo/resources/documents/DW/Dw2.htm
"Azolla, which is a member of the fern family grows extensively in 
association with nitrogen fixing bacteria, which allows it to produce on 
waters low in N but containing phosphorus. Azolla has been 
comprehensively discussed by van Hove (1989)."

> Dieter