The search for a sustainable slow-release fertilizer -- a key to sustaining global food production at a time of burgeoning population growth -- has led scientists to an ingredient used in some diarrhea medicines. They describe use of the substance, attapulgite, as a "carrier" for plant nutrients in a report in ACS' journal Industrial & Engineering Chemistry Research.

Boli Ni and colleagues explain that about half of the 150 million tons of fertilizer used worldwide every year goes to waste. That's because most fertilizers release nutrients too fast for the crops to use. The rest can run off farm fields and create water pollution problems. Existing slow-release fertilizers have drawbacks. So Ni's team turned to the environmentally friendly substance attapulgite, an inexpensive, nutrient-rich clay used for decades to treat diarrhea and for other applications. It once was an ingredient in the Kaopectate marketed in the United States. They also included guar gum, used in cosmetics and to thicken foods, and humic acid from decayed plant material.

The report describes development and successful tests of a new fertilizer composed of those three ingredients. The slow-release pellets were easy to prepare, reduced nutrient loss via runoff and leaching, improved soil moisture content and regulated soil acidity and alkalinity. "All of the results indicate that it may be expected to have wide applications for sustainable development of modern agriculture," the scientists say.

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The authors acknowledge funding from the Ministry of Education in China and Gansu Province Project of Science and Technologies.

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