Crop fertilizers are a major source of pollution, as the chemicals make their way out of the soil and into the natural environment. Scientists are now working on a possible solution to that problem, by developing a sustained-release fertilizer that takes the form of tiny glass beads.
Conventional fertilizers are typically applied to the soil as either a liquid, powder, or granules.
Whichever the case, the substance usually doesn't have a chance to release all of its nutrients before it either leaches down into the water table, or evaporates up into the atmosphere. The former results in waterway pollution and toxic events such as algae blooms, whereas the latter produces greenhouse gases such as nitrous oxide.
Making matters worse, because much of the fertilizer's nutritional payload doesn't reach the plants' roots in a single application, farmers must perform multiple applications in order to get the full effect. Not only does this task release even more pollutants into the environment, it's also extra work and an added expense for the farmers themselves.
That's where the little glass beads come in.
They were created by a team of Brazilian scientists, who started by producing a solid piece of water-soluble oxide glass containing common fertilizer nutrients such as phosphorus, calcium, and potassium. That glass was then ground into particles ranging from 0.85 to 2 millimeters in width (for reference, grains of sand range from around 0.1 to 2 mm). The idea was that as those particles/beads dissolved in moist soil, they would gradually release the nutrients.
In greenhouse tests, plots of Palisade lawn grass were fertilized just once with either the glass beads or with a liquid fertilizer containing the same amounts of the same nutrients. All of those plots were cut and harvested 45 days later, followed by four other harvests performed once every 30 days (allowing the grass to grow back between harvests).
Although both forms of fertilizer caused an initial boost in growth immediately after application, the bead-fertilized plots ultimately produced approximately 70% more biomass as measured across the five harvests.
And importantly, the beads were harmlessly taken up by the soil as they dissolved. In ecotoxicity tests performed on lettuce and onion seeds, the glass particles weren't found to have any effect on germination rates or cell health as compared to traditional fertilizers.
Finally, as an added bonus, the beads may also help plants grow by aerating their roots. The scientists were inspired by a previous study, in which particles of recycled bottle glass were shown to help oxygenate plants' roots while maintaining optimal moisture levels.
A paper on the current study, which is being led by the University of São Paulo's José Hermeson da Silva Soares, was recently published in the journal ACS Agricultural Science & Technology.
Source: American Chemical Society
