Why you should care
As populations surge and global temperatures rise, we need new solutions for feeding people.
Each year, farmers around the globe apply more than 100 million tons of fertilizer to crops, along with more than 800,000 tons of glyphosate, the most commonly used agricultural chemical and the active ingredient in Monsanto’s herbicide Roundup. It’s a quick-and-dirty approach: Plants take up less than half the phosphorus in fertilizer, leaving the rest to flow into waterways, seeding algae blooms that can release toxins and suffocate fish. An estimated 90 percent of the pesticides used on crops dissipates into the air or leaches into groundwater.
With the global population on pace to swell to more than nine billion by 2050 amid the disruptions of climate change, scientists are racing to boost food production while minimizing collateral damage to the environment. To tackle this huge problem, they’re thinking small — very small, as in nanoparticles a fraction of the diameter of a human hair. Three of the most promising developments deploy nanoparticles that boost the ability of plants to absorb nutrients in the soil, nanocapsules that release a steady supply of pesticides and nanosensors that measure and adjust moisture levels in the soil via automated irrigation systems.
Existing technology could increase average yields up to threefold in many parts of Africa.
It’s all part of a rise in precision agriculture, which seeks a targeted approach to the use of fertilizer, water and other resources. Recognizing the potential impact of nanotechnology, the U.S. Department of Agriculture’s National Institute of Food and Agriculture (NIFA) beefed up funding between 2011 and 2015, from $10 million to $13.5 million. India, China and Brazil are also joining the latest green revolution.
Scientists led by Pratim Biswas and Ramesh Raliya at Washington University in St. Louis have harnessed fungi to synthesize nanofertilizer. When sprayed on mung bean leaves, the zinc oxide nanoparticles increase the activity of three enzymes in the plant that convert phosphorus into a more readily absorbable form. Compared to untreated plants, nanofertilized mung beans absorbed nearly 11 percent more phosphorus and showed 27 percent more growth with a 6 percent increase in yield.
Raliya and his colleagues are also developing nanoparticles that enhance plants’ absorption of sunlight and investigating how nanofertilizers fortify crops with nutrients. In a study earlier this year, they found that zinc oxide and titanium dioxide nanoparticles increased levels of the antioxidant lycopene in tomatoes by up to 113 percent. Next, they want to design nanoparticles that enhance the protein content in peanuts. Along with mung beans, peanuts are a major source of protein in many developing countries.
Others are exploring nanoparticles that protect plants against insects, fungi and weeds. The Connecticut Agricultural Experiment Station and other institutions recently began field trials that use several types of metal oxide nanoparticles on tomato, eggplant, corn, squash and sorghum plants in areas infected with fungi known to threaten crops. Researchers led by Leonardo Fernandes Fraceto, of the Institute of Science and Technology, São Paulo State University, Campus Sorocaba, are designing slow-release nanocapsules that contain two types of fungicides or herbicides to reduce the likelihood of targeted fungi and weeds developing resistance. Scientists at the University of Tehran are conducting similar research. Still others are working on nanocapsules that release plant growth hormones.
“A lot of [this technology] is still in the development stages,” says Sonny Ramaswamy, director of NIFA. “Part of it is being driven by a complete lack of knowledge of the environmental state of these things.” Since researchers have only just begun investigating the safety of microscopic delivery mechanisms, a regulatory framework that specifically addresses these systems in agriculture does not exist. Scaling down a chemical might dramatically change its properties, possibly making it more likely to accumulate in streams and other habitats, says Stacey Harper, assistant professor in the School of Chemical, Biological, and Environmental Engineering at Oregon State University. In a recent study with zebra fish, Harper and her colleagues found that enveloping insecticides in minuscule capsules made them more toxic, probably because of increased uptake.
Plus, researchers still need to optimize nanoparticle synthesis for commercial use. It’s “not an easy system to scale up,” Fraceto says. NIFA’s Ramaswamy predicts that smart systems consisting of tiny sensors will “grow very rapidly,” while nanopesticides and other products will be “a little bit slower to come around.”
If nanotechnology does take hold in agriculture, who will have access to it? Will only affluent countries reap the benefits? “We should be concerned about bridging the gap between the developing and developed world,” says Chike Mba of the U.N.’s Food and Agriculture Organization. In the meantime, farmers in developing countries can tap into effective low-tech options. Existing technology could increase average yields up to threefold in many parts of Africa, according to research by the U.K.’s Foresight Programme.
Genetically modified crops have been met with resistance, but Washington University’s Raliya believes the public will be less wary of nanotechnology since it doesn’t fundamentally alter crops and ultimately reduces chemical use — a bit like organic farming. “We’re currently not able to produce enough food for the people who live on this planet,” says Jason White, vice director of the Connecticut Agricultural Experiment Station and head of its Department of Analytical Chemistry. “The population is increasing, the climate is changing, making agriculture hard to do. The role of nanoparticles is to help us address this major problem. We just can’t produce enough food.”