Slow-release nanofertilizer could boost crop yields

Nitrogen fertilizers used to grow crops around the globe have a problem. More than three-quarters of their nutrients get washed away before plants can absorb them, wasting money and creating environmental messes downstream. Now, researchers have developed nanoparticle fertilizers that release nutrients slowly over a week, giving crops more time to take them up (ACS Nano 2017, DOI: 10.1021/acsnano.6b07781).

Conventional slow-release fertilizers consist of urea coated in water-insoluble sulfur or polymers. Such fertilizers reduce runoff that can lead to harmful algal blooms in waterways, says Gehan Amaratunga of the University of Cambridge. But these fertilizers are expensive and haven’t been shown to increase crop yield. Amaratunga and his colleagues decided to try a new strategy: They attached nitrogen-laden urea molecules to nanoparticles of hydroxyapatite, a naturally occurring form of calcium phosphate.

In water, the urea-hydroxyapatite combination released its nitrogen payload over the course of a week, compared with pure urea, which released its nitrogen over a few minutes. When tested on rice crops in Sri Lanka, the nanofertilizer increased yields by 10%, even though it delivered only half the amount of urea compared with traditional fertilizer.

Richard Liu of Ohio State University says the nanocomposite fertilizer looks more promising than other slow-release options for increasing crop yields and reducing costs and environmental risks. He expects that it could be used in most agricultural areas around the globe and on a variety of crops, such as wheat, corn, and soybeans.