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Fertilizer of the future


While nitrogen is key to high yields, between 50 and 70 per cent of the nitrogen applied in fertilizer is lost to the environment. This is costly for farmers and leads to environmental contamination.

Now researchers are using nanotechnology to ensure that nitrogen is released from the fertilizer only as the crop needs it. This smart fertilizer will save farmers money while reducing water pollution and reducing greenhouse gas emissions.

Nanotechnology has been touted as the next big thing for decades, with a growing number of applications ranging from computing to textiles to medical advances. Carlos Monreal, a researcher with Agriculture and Agri-Food Canada and an adjunct professor at Carleton University in Ottawa, has turned his attention to nanotechnology applications that will benefit agriculture.

First coined in the early 1980s, nanotechnology refers to the ability to control individual atoms and molecules. The nanoscale is less than 100 nanometres, and one nanometre is a billionth of a metre (to demonstrate the scale involved, a sheet of newspaper is about 100,000 nanometres thick). Advances in laboratory equipment have made it possible for scientists to manipulate matter at the molecular level, which is much too small to be seen by ordinary microscopes.

Monreal, who first began working on the project in 2007, explains the rationale behind this nanotechnology breakthrough in simple terms. Soil microbes oxidize nitrogen found in proteins and nucleic acids in the soil organic matter into ammonium and nitrate, forming what the plant uses for growth and to make grain and foliage. When the nitrogen concentration in the soil water around the plant roots dips to a level where it becomes limiting to plant growth, the plant releases chemicals that signal the soil microbes to make more nitrogen available in a form the plants can use. In return, the microbes receive carbon substrates from the plant roots.

By identifying the molecular composition of these chemical signals that are produced by the plant roots and found in the soil solution, it is possible to wrap urea fertilizer in a polymer film with a biosensor that only releases the nitrogen in response to these chemical signals.

Monreal is confident his research will be successful but says it takes time to get the product to the commercial stage. His first step was to identify the molecular composition of the chemical signals produced by wheat and canola when they needed more nitrogen in the lab.

Then Maria DeRosa, another researcher at Carleton University, was able to develop a biosensor that binds to the chemical signal being emitted by the plant roots. When this biosensor, which is a piece of DNA known as an aptamer, is housed in a polymer film around the urea, it distorts the film and enhances the exit of the urea thereby making its nitrogen available to the crop.

By 2012, Monreal had an early working prototype. Now he is working on an advanced prototype. “I am focusing on developing the polymer material that would be functional in soil,” he says. He hopes to soon be able to test the prototype in the greenhouse with wheat and canola crops.

This nanofertilizer is a win-win solution with no drawbacks, says Monreal. The nanofertilizer prevents nitrogen from being lost through leaching of water-soluble forms, emission of gaseous ammonia and nitrous oxide or by being tied up as mineral nitrogen in the soil organic matter by microbes. “And the biosensor and polymer are completely biodegradable,” he continues.

This is only one application of nanotechnology for fertilizers, says Monreal. There are three ways that nanofertilizers may deliver nutrients. The nutrient may be encapsulated inside nanomaterials or nanoporous materials, coated with a thin protective polymer film, or delivered as particles or emulsions of nanoscale dimensions. “Owing to the high surface area to volume ratio, the effectiveness of nanofertilizers may surpass the most innovative polymer-coated conventional (non-nanotechnology) fertilizers, which have seen little improvement in recent years,” Monreal says.

There are other applications for nanotechnology in agriculture. Nanotechnology will make it possible to more fully understand the complex system of soil and roots at the molecular level, says Monreal. He is working on a project to identify which of the bacteria in the rhizosphere (the soil and water zone around the plant roots) are important for nitrogen mineralization during crop growth. He also hopes to be able to use advances in chemistry and molecular biology to get a better understanding of how soil organic matter stabilizes soil.

This research is funded by Alberta Innovates Bio Solutions, a research agency funded by the Government of Alberta that helps industry solve challenges with solutions that deliver economic, environmental and social benefits.

May 17, 2016
By Helen Lammers-Helps