Zinc nano particles can substitute nitrogen and phosphorous fertilizers to increase plant growth sans water pollution

Bengaluru: Indian-origin researchers in the US have shown that zinc nanoparticles can substitute nitrogen and phosphorous fertilisers to increase plant growth without causing water pollution - a serious problem with conventional fertilisers.

A nanoparticle is an ultrafine object that behaves as a whole unit in terms of its properties.

Fertilisers, which provide nutrients needed for plant growth, are traditionally 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 scientist Ramesh Raliya and Pratim Biswas, chairman of the Department of Chemical Engineering at the Washington University in St Louis, report that zinc nanoparticles may provide a better approach to fertilise the plants. They say their experiments on mung bean (also known as green gram) plants show this approach is environment friendly and can potentially reduce the use of conventional fertilisers.

"Currently, farmers are using nearly 85 percent of the world's total mined phosphorus as fertiliser. At this rate, the world's supply of phosphorus could run out within the next 80 years," the scientists report in the Nanowerk Nanotechnology News online journal.

"Use of zinc nanoparticles can help conserve natural mineral reserves and energy and reduce water contamination. It also can 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 27 percent increase in biomass and produced six percent more beans than plants that were grown using typical farm practices but no fertiliser, they report. Mung beans are a high source of protein, fibre and antioxidants and the plants are widely grown for food in Asia.

According to the report, zinc nano-fertiliser is environment friendly as it can be directly sprayed on to the 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 fertiliser 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 fertiliser use, which involves many tonnes of inputs, nanotechnology focusses 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 nanoparticle 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 nanofertilizers 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."

By K.S. Jayaraman

(The author can be contacted at [email protected])