Re: water for food ->Alternative Systems
As an aside to the discussion on how much water it takes to produce
food, read below for an introduction to two water conserving production
systems that are not well known, but making headways on small
Aquaponics, the integration of recirculating aquaculture and
hydroponics, is gaining recognition for many reasons, one of which
is the minimal water usage required to produce hydroponic vegetables.
The affluent from tilapia fish tanks are used to fertigate hydroponic
vegetable-herb beds, and the plant roots and bacteria living in the hydroponic
media function as biofilters in the removal of waste nutrients. The
cleaned-up water is then returned to the fish tanks.
Mark McMurtry and Doug Sanders of North Carolina State University
were intrumental to advance this technology back in the 80's. One of
McMurtry's stated intentions was to take this system to arid regions of
Africa, since aquaponic water re-use enables vegetable production to
take place where field irrigation is not feasible.
As an example, Tom & Paula Sperraneo's original aquaponic system
in West Plains, MO, consisted of a 500 gallon tank. In the course of a week,
35 gallons of water was used to replenish the tank. The volumes of
water tied up in the pounds and pounds of tomatoes and cucumbers raised
in the hydroponic beds could account for most of the water loss.
An interesting fact is that 15 years ago, aquaponics did not perform
well despite much research. Partly, the successful aquaponic
operations scattered around the country today are due to a shift
from mechanical filters, where the "goodies" were source separated,
to simple constructed wetland-type biofilters where the nutrients
are allowed to be removed by plant vegetation, has made all of the
difference in the world.
I offer this info in the context of an emerging alternative production
system that is--in addition to being extremely water conserving--making
a difference for some small farmers and greenhouse operators operating
in niche markets; it will not, of course, replace field production
(though is quite feasible that a portion of vegetable sales in the
winter months could be supplied through local greenhouse vegetable
production rather than through shipped-in produce).
The Sunbelt-HydroSource Dryland Bed production system (the
progeny of Dan Wofford of Western Polyacrylamide Inc. of Jay,
Oklahoma), is an integrated minimum-till, no-weed, minimal-irrigate
plant production system. It combines a hydrogel (HydroSource) with
a long-lasting, heavy duty polypropylene geotextile (DeWitt Sunbelt Weed
Barrier). A third component is the use of Booth tubes, which are 3-inch
by 0.5-inch plastic tubes filled with a potting mix and planted to
seedlings (384 cell trays).
Sunbelt rolls are 300'x15', thus many small farmers are planting out
a 4500 sq. ft. bed of watermelons, cantaloupes, tomatoes, peppers,
squash, or strawberries. More than 100 small growers from Missouri
have implemented this system in the last year alone. One of these
farms has a SARE-grant to raise day-neutral strawberries via this
The option exists to plant no-till, though some soils and sites are
better treated through tillage. Heavy application rates of compost--very
important for long-term availability of nutrients--is incorporated into
the soil, or heaped onto the surface of a no-till bed. Next, the
hydrogel is surface broadcast at 10-40 lbs/1,000 sq. ft, though
application rates are creeping up to 20-60 lbs/1,000 sq. ft. If water
is available from a hose or tank, the dry crystal is watered down prior to
laying the weed barrier. If not, you depend of rainfall to moisten the
hydrogel. When the weed barrier is layed down, it is pinned at the edges.
Booth tube seedlings are transplanted through the weed barrier, after
poking a hole in the geotextile, thus creating a very tight fit that
eliminates exposure of bare soil....and thus weeds are virtually
eliminated, requiring only minimal occassional hand pulling of
Once installed, such beds can produce up to ten years with no
additional tillage, minimal weeding, and zero to minimal irrigation
The water-saving features lie in the tight weave of the Sunbelt
weed barrier, which cuts down on evapotranspiration loss (though
it is breathable to oxygen and rainfall), and in the hydrogel itself.
In most growing seasons, periodic rainfall serves to recharge the
water absorbing hydrogel. Reduced irrigation may be required under
The enormous impact of this system to small farm agriculture
is readily apparent when you consider the elimination of weeds
and watering in watermelons, cantaloupes, cut flowers, etc., etc.
ATTRA Technical Specialist