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“Slow-release” N hybrid shows potential

A popular fertilizer for farmers is urea, a nitrogen-rich organic compound found in human urine. Urea is water soluble and volatile, which means that irrigation or a heavy rains often sweeps it away in surface run-off or it escapes as a gas before it can be absorbed by plants.


February 8, 2017
By Katherine Kornei Science Magazine

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Researchers have now developed a new time-released fertilizer that slowly discharges its cargo. When applied to rice fields in Sri Lanka, crop yields increased, even when only half the typical amount of nutrients was added.

“Up to 70% of urea is lost to the environment,” says Nilwala Kottegoda, a materials scientist at the Sri Lanka Institute of Nanotechnology in Homagama and lead author of the study. That’s bad news for farmers, whose budgets are already stretched thin – and the environment: Fertilizer run-off into rivers, lakes, and deltas is a primary cause of algal blooms that are toxic to aquatic life.

Kottegoda and her team have developed a new formulation of urea that works like a time-released drug capsule. The researchers attached urea molecules to hydroxyapatite – a constituent of human bones and teeth – in a six-to-one ratio by weight. The chemical bonds between the urea and hydroxyapatite molecules prevent the urea from decomposing too quickly. Yet, they do break down over time, which results in a controlled release of nitrogen at a rate that plants can absorb. | READ MORE