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How nanotechnology can help us grow
more food using less energy andwater
May 25, 2016 9.23pm EDT
Ramesh Raliya
Research Scientist, Washington University in St Louis
Pratim Biswas
Chairman, Department of Energy, Environmental and Chemical Engineering, Washington
University in St Louis
The Conversation’s partners
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With the world’s population expected to exceed nine billion by 2050, scientists are working to
develop new ways to meet rising global demand for food, energy and water without increasing
the strain on natural resources. Organizations including the World Bank and the U.N. Food
and Agriculture Organization are calling for more innovation to address the links between
these sectors, often referred to as the food-energy-water (FEW) nexus.
Treated with zinc nanoparticles, mung bean plants like these grew larger and produced more beans.
Chad Zuber/Shutterstock.com
Nanotechnology – designing ultrasmall particles – is now emerging as a promising way to
promote plant growth and development. This idea is part of the evolving science of precision
agriculture, in which farmers use technology to target their use of water, fertilizer and other
inputs. Precision farming makes agriculture more sustainable because it reduces waste.
We recently published results from research in which we used nanoparticles, synthesized in
our laboratory, in place of conventional fertilizer to increase plant growth. In our study we
successfully used zinc nanoparticles to increase the growth and yield of mung beans, which
contain high amounts of protein and fiber and are widely grown for food in Asia. We believe
this approach can reduce use of conventional fertilizer. Doing so will conserve natural mineral
reserves and energy (making fertilizer is very energy-intensive) and reduce water
contamination. It also can enhance plants' nutritional values.
Impacts of fertilizer use
Fertilizer provides nutrients that plants need in order to grow. Farmers typically apply it
through soil, either by spreading it on fields or mixing it with irrigation water. A major portion of
fertilizer applied this way gets lost in the environment and pollutes other ecosystems. For
example, excess nitrogen and phosphorus fertilizers become “fixed” in soil: they form
chemical bonds with other elements and become unavailable for plants to take up through
their roots. Eventually rain washes the nitrogen and phosphorus into rivers, lakes and bays,
where it can cause serious pollution problems.
Fertilizer use worldwide is increasing along with global population growth. Currently farmers
are using nearly 85 percent of the world’s total mined phosphorus as fertilizer, although plants
can uptake only an estimated 42 percent of the phosphorus that is applied to soil. If these
practices continue, the world’s supply of phosphorus could run out within the next 80 years,
worsening nutrient pollution problems in the process.
Applying fertilizer the conventional way can waste resources
and contribute to water pollution.
Fotokostic/Shutterstock.com
Phosphate mine near Flaming Gorge, Utah. Jason Parker-
In contrast to conventional fertilizer use, which involves many tons of inputs, nanotechnology
focuses on small quantities. Nanoscale particles measure between 1 and 100 nanometers in
at least one dimension. A nanometer is equivalent to one billionth of a meter; for perspective,
a sheet of paper is about 100,000 nanometers thick.
These particles have unique physical, chemical and structural features, which we can fine-
tune through engineering. Many biological processes, such as the workings of cells, take
place at the nano scale, and nanoparticles can influence these activities.
Scientists are actively researching a range of metal and metal oxide nanoparticles, also
known as nanofertilizer, for use in plant science and agriculture. These materials can be
applied to plants through soil irrigation and/or sprayed onto their leaves. Studies suggest that
applying nanoparticles to plant leaves is especially beneficial for the environment because
they do not come in contact with soil. Since the particles are extremely small, plants absorb
them more efficiently than via soil. We synthesized the nanoparticles in our lab and sprayed
them through a customized nozzle that delivered a precise and consistent concentration to the
plants.
We chose to target zinc, which is a micronutrient that plants need to grow, but in far smaller
quantities than phosphorus. By applying nano zinc to mung bean leaves after 14 days of seed
germination, we were able to increase the activity of three important enzymes within the
plants: acid phosphatase, alkaline phosphatase and phytase. These enzymes react with
complex phosphorus compounds in soil, converting them into forms that plants can take up
easily.
When we made these enzymes more active, the plants took up nearly 11 percent more
phosphorus that was naturally present in the soil, without receiving any conventional
phosphorous fertilization. The plants that we treated with zinc nanoparticles increased their
biomass (growth) by 27 percent and produced 6 percent more beans than plants that we grew
using typical farm practices but no fertilizer.
Burlingham/Wikipedia, CC BY
Algae bloom in Lake Erie in 2011, caused by phosphorus in
runoff from surrounding farms. NASA Earth
Observatory/Flickr, CC BY
Nanofertilizer also has the potential to increase plants' nutritional value. In a separate study,
we found that applying titanium dioxide and zinc oxide nanoparticles to tomato plants
increased the amount of lycopene in the tomatoes by 80 to 113 percent, depending on the
type of nanoparticles and concentration of dosages. This may happen because the
nanoparticles increase plants' photosynthesis rates and enable them to take up more
nutrients.
Lycopene is a naturally occurring red pigment that acts as an antioxidant and may prevent cell
damage in humans who consume it. Making plants more nutrition-rich in this way could help
to reduce malnutrition. The quantities of zinc that we applied were within the U.S.
government’s recommended limits for zinc in foods.
Next questions: health and environmental impacts of
nanoparticles
Nanotechnology research in agriculture is still at an early stage and evolving quickly. Before
nanofertilizers can be used on farms, we will need a better understanding of how they work
and regulations to ensure they will be used safely. The U.S. Food and Drug Administration
has already issued guidance for the use of nanomaterials in animal feed.
Manufacturers also are adding engineered nanoparticles to foods, personal care and other
consumer products. Examples include silica nanoparticles in baby formula, titanium dioxide
nanoparticles in powdered cake donuts, and other nanomaterials in paints, plastics, paper
fibers, pharmaceuticals and toothpaste.
Many properties influence whether nanoparticles pose risks to human health, including their
size, shape, crystal phase, solubility, type of material, and the exposure and dosage
concentration. Experts say that nanoparticles in food products on the market today are
probably safe to eat, but this is an active research area.
Addressing these questions will require further studies to understand how nanoparticles
behave within the human body. We also need to carry out life cycle assessments of
nanoparticles' impact on human health and the environment, and develop ways to assess and
manage any risks they may pose, as well as sustainable ways to manufacture them.
However, as our research on nanofertilizer suggests, these materials could help solve some
of the word’s most pressing resource problems at the food-energy-water nexus.
Nanotechnology
Nutrition
fertilizer
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