DirT? Who NEedS It?
Is Poised to Change
By Mallory Pickett
CLOSE TO 7.2 BILLION PEOPLE LIVE on our planet today; and the world’s population keeps increasing, with a projected population of 8 to 9 billion
in 2030 and 8 to 11 billion in 2050. Unfortunately, the planet cannot keep pace with this
ever-increasing human population. In fact, the
amount of land suitable for agriculture, and
the stores of water needed to grow crops are
shrinking, as the climate gets warmer. So,
how will people feed themselves?
It will take some ingenuity to find a way to
thrive in a hot and crowded planet, and one
innovation in agriculture appears promising:
farmers and scientists have come up with a
way to grow the same amount of food using
60% to 90% less water and as little as one-tenth of the land. They do it by skipping soil
altogether. This is the fastest growing field in
agriculture, and it is called hydroponics.
What is hydroponic
Hydroponics is the agricultural technique of
growing plants in water instead of soil. Plants
need a specific set of chemical nutrients to
grow, and there is no reason they have to
get those nutrients from dirt. Most plants are
composed of approximately 72% water, 24%
organic material, and 4% inorganic compo-
nents, such as nitrogen and phosphorous.
All they need is sunlight and air to build the
organic material, and they traditionally absorb
water and nutrients from the soil—but dirt
itself is not necessary for growth (Fig. 1).
People have been growing plants in water
and other soil-less environments for thousands of years. Some historians speculate
that the hanging gardens of Babylon grew in
water, and ancient Egyptian records describe
growing plants in water along the Nile.
But the method did not take off beyond
these ancient civilizations, because it was difficult to make it as productive as traditional
agriculture. Difficult, that is, without understanding the chemistry of soil and water. Modern chemistry was not developed until the late
18th century, but once it was, chemists were
able to help make hydroponics even more
productive than traditional agriculture.
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Designing efficient and productive hydroponic systems became possible after 19th-
century scientists determined how plant
growth worked. Scientists did not understand
Figure 1. A typical hydroponic system, called a nutrient film technique, has a constant flow of nutrient
solution coming from a submersible pump. The nutrient solution is pumped into the growing tray and
flows over the roots of the plants. The solution then drains back into the reservoir. The plants are
supported in a small plastic basket with the roots dangling into the nutrient solution. R S
14 ChemMatters | OCTOBER/NOVEMBER 2015 www.acs.org/chemmatters