Pratim Biswas, a research scientist at Washington University, is part of a team that found zinc nanoparticles can substitute nitrogen and phosphorous in fertilizers to increase plant growth without causing water pollution. ( photo)

BENGALARU — Indian American researchers at Washington University in St. Louis, Mo., have developed a fertilizer made of zinc nanoparticles that boosts plant growth without contaminating water — a serious problem with conventional fertilizers.

Conventional nitrogen and phosphorus fertilizers, which provide nutrients needed for plant growth, are applied to the soil either by spreading them on fields or mixing them with irrigation water. Excess nitrogen and phosphorus, unused by the plants, eventually get washed into rivers and lakes, polluting the water.

Research scientists Ramesh Raliya and Pratim Biswas, chairman of the Department of Chemical Engineering at Washington University, report that zinc nanoparticles may provide a better approach to fertilize the plants. A nanoparticle is an ultra fine object that behaves as a whole unit in terms of its properties.

They say their experiments on mung bean (also known as green gram) plants have showed that this approach is environmentally friendly and can potentially reduce the use of conventional fertilizers.

“Currently, farmers are using nearly 85 percent of the world’s total mined phosphorus as fertilizer. At this rate, the world’s supply of phosphorus could run out within the next 80 years,” the scientists reported in the online journal Nanowerk Nanotechnology News. 

“Use of zinc nanoparticles can help conserve natural mineral reserves and energy, and reduce water contamination. It can also enhance the plants’ nutritional values,” they say.

In their experiments, the scientists used zinc nanoparticles synthesized in their laboratory on mung bean plants. The plants grew larger with a 27 percent increase in biomass and produced 6 percent more beans than plants that were grown using typical farm practices but no fertilizer, they report. Mung beans are a high source of protein, fiber and antioxidants, and the plants are widely grown for food in Asia.

According to the report, zinc nano-fertilizer is environmentally friendly, as it can be directly sprayed onto plant leaves without coming into contact with soil. Since the particles are extremely small, plants absorb them more efficiently than via soil. In their experiments, they sprayed the zinc nanoparticles through a customized nozzle directly on the leaves of mung bean plants.

Nano-fertilizer also has the potential to increase plants’ nutritional value, the scientists report. In a separate study, they found that applying titanium dioxide and zinc oxide nanoparticles to tomato plants increased the content of “lycopene,” an antioxidant in the tomatoes, by 80 to 113 percent.

“Making plants more nutrition-rich in this way could help to reduce malnutrition,” they said.

In contrast to conventional fertilizer use, which involves many tons of inputs, nanotechnology focuses on small quantities.

“These particles have unique physical, chemical and structural features, which we can fine-tune through engineering,” the researchers said, adding that they chose zinc nanoparticles for their studies, since zinc is “a micro-nutrient that plants need to grow but in far smaller quantities than phosphorus.”

The researchers, however, cautioned that before nano-fertilizers can be used on farms, “we will need further studies to understand how nanoparticles behave within the human body and regulations to ensure they will be used safely.”

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