doi:10.1038/nindia.2016.121 Published online 15 September 2016
Nanoparticles can boost the growth of mung bean plants by increasing their nutrient uptake from soil, a new study finds1.
Because the nanoparticles are prepared using a soil fungus, this technique is safe and significantly increases soil phosphorous over the life cycle of the plant, from seed to harvest, according to the study.
Food crops such as mung bean use phosphorous to grow. If farmers continue to spread phosphorous fertilizers on crops at the current rate, the world’s phosphorous reserve will deplete in 80 years.
To devise an eco-friendly alternative, researchers turned their attention to zinc, an essential trace element known to boost the activities of enzymes such as phosphatases and phytase that convert soil phosphorous into a form that plants can absorb.
They synthesized zinc oxide nanoparticles using a soil fungus and sprayed the nanoparticles on the leaves of mung bean plants. They then monitored the plants’ growth and the activities of the phosphorous-mobilizing enzymes in soil that surrounds the plant root and found the nanoparticles significantly enhanced the activities of enzymes such as phosphatase and phytase, increasing the plants’ phosphorous uptake by almost 11%. These particles also increased root volume, stem height and phosphorous-mobilizing soil microbial population.
“This will reduce the rampant use of phosphorous fertilizer made from rock phosphate, saving energy and natural resources,” said Ramesh Raliya, lead author of the study from the Washington University in St. Louis, USA. The technology will also check water pollution by reducing the chances of phosphorous run-off that pollutes water streams and causes harmful algal growth, Raliya told Nature India.
This technology holds promise as it will help farmers to fine-tune phosphorous fertilization, said Mainak Das who studies the role of nanoparticles in food crop yields at the Indian Institute of Technology, Kanpur, and was not involved with the research. The researchers had clearly shown that the concentration of zinc was within the limit of dietary recommendation, Das added.
To assess safety, the researchers measured the toxic effects of the nanoparticles in the plants and found they did not accumulate in the mung bean seeds beyond the safe limit. In addition, the nanoparticles are coated with fungal proteins that prevent the direct contact between soil and the nanoparticles, indicating that the technology is safe, Raliya explained.
Field studies in India were also encouraging for other crops with almost 35% soil phosphorous mobilization and yield spurts between 25% and 32%, said Jagadish Chandra Tarafdar, co-author of the study from the Central Arid Zone Research Institute, India.
1. Raliya, R. et al. Enhancing the mobilization of native phosphorus in the mung bean rhizosphere using ZnO nanoparticles synthesized by soil fungi. J. Agr. Food. Chem. 64, 3111-3318 (2016)