permaculture

["Scott Pittman" <scott@permaculture.org>]

Farmers have been irrigating with salt water for centuries in arid climates
and the problem is the slow accumulation of salts in the soil profile.  The
only way to eliminate this salt is to wash it out with lots of water and
send the salt laden wash water down the river, that is why the Spanish
acequia systems had tail ditches at the end of the fields.  As we are
confronted with less and less volume of water in the riparian sectors of the
arid southwest the practice of flushing out the soils is being lost and salt
accumulations have reached alarming percentages. Most farmers no longer dig
tail drains at the bottom of fields.  This is often not the fault of the
farmer but that he has to make a choice of watering his crop of using the
water to flush out his soil - there isn't sufficient volume to do both.  

There is also the compounding problem of the less water there is the less
hydrologic pressure in the irrigation ditches which diminishes the
efficiency of flood irrigation.  Many fields in northern New Mexico become
progressively more salted the further down the field since the water has
insufficient head to reach the end of the rows.

If I were to use seawater for irrigation it would certainly not be in soil
based agriculture - mayhaps hydroponics.  In past history conquering armies
would salt the agricultural land to insure that the conquered people did not
return to threaten them in the future.  If you look at a lot of the land of
the middle east it is no longer viable for agriculture because of salting
and deforestation, which are two sides of the same coin. The Nile delta of
Egypt has had such a long history of agriculture because of the seasonal
floods that provide enough water to wash the salt from the soil for another
season.

Scott Pittman
Director
Permaculture Institute
www.permaculture.org
-----Original Message-----
From: Lawrence F. London, Jr. [mailto:lflj@intrex.net] 
Sent: Friday, August 03, 2007 10:53 PM
To: permaculture
Subject: [permaculture] Tomatoes Grown in Seawater Healthier Than Regular
Kind


Tomatoes Grown in Seawater Healthier Than Regular Kind
http://www.foxnews.com/story/0,2933,260468,00.html?sPage=fnc.science/natural
science

Tomatoes irrigated with diluted seawater grow with significantly higher
levels of
healthy antioxidant compounds, new research shows.

"It'd be interesting to see if this might be a more general phenomenon,
where a little
salt induces antioxidants in lots of crops," said botanist Edward Glenn at
the
University of Arizona, who did not participate in the new study. "There
could be a
consumer wave toward salt-tolerant crops based on their nutritional
properties."

The option to use salty water on crops might help farmers deal with growing
irrigation
woes. Irrigation water, as well as drinking water, is growing scarce and
deteriorating
in quality around the world.

Nearly 70 percent of all available freshwater is used for agriculture. Use
of water for
irrigation has increased globally by more than 60 percent since 1960,
according to
United Nation statistics.

At the same time, poor irrigation and drainage practices have led to salt
buildup in
roughly one-eighth of all irrigated land.

Although desalination plants that remove salt from saltwater now exist, they
remain
expensive. For example, distillation processes that separate out any
dissolved minerals
by boiling and condensing water require costly amounts of fuel.

Riccardo Izzo at the University of Pisa in Italy and his colleagues reasoned
that
diluted saltwater could drive crops to generate more healthy antioxidants,
such as
vitamins C or E. Plants generate antioxidants to protect themselves when
stressed out by
salt, drought or various other burdens.

The researchers investigated tomatoes, which are grown worldwide and are
moderately
saline-tolerant. They grew various types of tomatoes, including those
commonly used for
salads, under different levels of salinity and investigated the fruit for
nutrients.

The researchers found that growing tomatoes in 10 percent seawater improved
antioxidant
levels significantly, findings they detailed in the April 4 issue of the
Journal of
Agricultural and Food Chemistry.

Glenn noted the water that percolates out from normally irrigated soil,
technically
known as irrigation return flow, is often as salty as 10 percent seawater.

"About a third of irrigation water becomes irrigation return flow, so
there's a huge
amount of this brackish water, and this research now suggests this could get
reused for
crops," Glenn told LiveScience.

For decades, research has shown that seawater can irrigate crops, "but
there's an
impression [that] the crops seawater can irrigate are low value," Glenn
said. "Farmers
want a good return for their investment and time, and tomatoes are really
high value.
Also, crops like tomatoes are sold based on consumer appeal, and if you have
an extra
going for you like high antioxidant levels, this could be quite valuable."