Gravity has been called a weak but
pervasive force. It’s also a force to be
reckoned with in hydroponics. Even
systems that aren’t specifically considered gravity-fed often rely on gravity
in one way or another.
This isn’t a big surprise since gravity is hard at work in nature. Plants
depend on it for more than just
delivering water in the form of rain.
Gravity and capillary action—the
ability of a liquid to flow through a
confined space against gravity—are
both dynamic forces essential for plant
health and development. In part, plants
use gravity to help direct their roots
downward into the soil (gravitropism)
and their stems upward toward the sun.
For the indoor gardener, gravity is often
put to use moving water and nutrients
through a growing system.
To understand how gravity-based
systems work, it’s useful to think of
water and nutrient delivery in terms of
ups and downs, or downs and ups. The
down part of the equation involves getting a prepared nutrient solution from
an elevated location, like a holding
tank, to a planting bed or network of
pots. We can see this in action in some
tower systems, vertical gardens, ebb and
flow systems and others. Water delivered to plants via a downward incline
uses gravity power to seek its own level.
In a well-planned system, that is in close
proximity to thirsty plant roots.
Harnessing gravity to power all or
a portion of a hydroponic system
makes good sense. It’s cost effective and saves labor, too. But what
happens after all that nutrient-laden
“ arnessing gravity to power all
H
or a portion of a hydroponic
system makes good sense.”
water completes the downward circuit? Gravity isn’t much help when
the goal is to get liquid to flow back
uphill. Addressing this issue is what
separates different types of gravitybased hydroponic technologies. The
oldest, developed for watering, uses
a pulley and a bucket. Once raised
and emptied, the bucket is lowered
to catch any runoff. It is raised again
and again to repeat the process.
Today, some gravity-fed systems use
a simple electric pump and a series
of pipes or tubes to handle the task
of recirculating water and plant food.
The tank or reservoir is located above
or below the plants, while water and
nutrients are pumped through a tube
for part of the cycle and allowed to flow
back into the reservoir after passing
through a series of tilted shelves, pots
or pipes containing plants. Add a timer,
fittings and a few minor accessories,
and you have an energy-efficient se t-up
that’s scalable and easy to maintain.
Putting one together makes for a pretty
straightforward DIY project.
As green as this sounds, there are
gravity-fed systems that require no
power source and still manage a high
degree of automation. They eliminate
the recirculating problem by supplying
nutrients from an elevated cistern in
small increments, allowing plant roots
to exhaust the supply before more is
released. There is no runoff or waste
to deal with. Looking at it another way,
the plants actually control the system,
as their uptake of the available nutrient
solution triggers a specially designed
valve to release more. Think of it as an
intuitive ebb and flow system, but one
that operates without electricity.
Many experts are hoping for big
things from energy-efficient, gravityfed hydroponics and other indoor
growing innovations. In areas of
the world where outdoor growing is
impractical, or will be impractical in
the decades to come, the development
of large-scale, reliable and planetfriendly agricultural solutions could
hold the key to feeding the Earth’s
projected human population of 9.6 billion souls by the year 2050. Until then,
whether you’re growing a tomato plant
in your home or a bumper crop of lettuce and herbs in your greenhouse or
grow tent, gravity is a powerful friend
to have in your corner.
Maximum Yield USA | January 2015
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