A nutrient-rich clay long used to treat diarrhea might help to solve a problem related to the *ahem* other end of the digestive tract. A new report shows that the mineral attapulgite could be useful as a sustainable slow-release fertilizer, a key ingredient for feeding the world’s growing population.
In ACS’ journal Industrial & Engineering Chemistry Research, Boli Noi and colleagues propose using the clay to release plant nutrients at a controlled rate to maximize their effect. They cite studies showing that plants take up less than half of the fertilizers applied to them.
This inefficiency is not only expensive, it wastes an increasingly precious resource. The world uses about 150 million tons of fertilizer each year -- enough to fill about 6.5 million semi-trucks. That number is expected to double by 2030 as the world’s population grows. What’s more, the excess fertilizer runs off into rivers, lakes and other waterways and causes pollution problems.
Attapulgite would control nutrient release, allowing plants to use the nutrients more efficiently and limiting their environmental impact. Slow-release fertilizers currently in use are imperfect. Some may not release all of their nutrients to the soil for plants to use. Others can make the soil more acidic or leave unwanted, lab-made compounds in the soil. Noi’s team argues that nutrient-rich attapulgite is more environmentally friendly, cheaper and more effective.
Before Noi and his team used it as a fertilizer, attapulgite – named for a town in southwest Georgia where the clay is abundant – was a main ingredient in a range of anti-diarrheal medicines, including Kaopectate. Although its U.S. formula changed in 2003, the over-the-counter drug still contains attapulgite in other Canada and other markets. In the digestive tract, it effectively absorbs toxins and acids.
They tested fertilizer pellets made from a mixture of attapulgite, humic acid from decayed plant material and guar gum, a thickener used in foods and cosmetics. The humic acid and guar gum coating helped to slow the release of nitrogen and phosphorous nutrients trapped in the clay. The coating also helped to trap water in the soil.
The group reports that their fertilizers were easy to make, produced less runoff, improved soil moisture and regulated soil acid and alkalinity. The authors conclude: “All of the results indicate that it may be expected to have wide applications for sustainable development of modern agriculture.”
Will smarter fertilizers help solve the looming food crisis brought on by the world’s population growth? Tell us your thoughts in the comments.