SEWING SEEDS OF INNOVATION

Another day, another new use for graphene. This two-dimensional form of carbon is strong, flexible and a great conductor of heat and electricity. As such, it's beginning to show up in everything: from batteries to bike tires, dental fillings to cancer treatments. Now the overachieving wonder material has been put to work in the garden, as Australian researchers have used it as an effective, slow-release carrier for fertiliser.

The study, conducted by PhD student Shervin Kabiri from the University of Adelaide, found that graphene's long list of useful properties made it an effective vessel for transporting and releasing essential plant nutrients into the soil. Specifically, the researchers used graphene oxide, a form of the material made up of carbon, oxygen and hydrogen atoms.

Boasting a very high surface area and a high charge density, graphene oxide is able to bind to more of the nutrient ions that plants need. That strength works to protect the mix from impact and abrasion damage during transportation, as well as release the nutrients slowly once it's spread out on the soil.

"We see the benefits of the materials are twofold," says Professor Mike McLaughlin, head of the Fertiliser Technology Research Centre at the University of Adelaide. "One is the nutrient release characteristics, but also that physical strength could be quite important for granular fertilisers, because degradation is a major issue for manufacturers."

The timing of the nutrient release is crucial. Many commercial fertilizers will release their entire payloads within 12 to 24 hours, but that doesn’t necessarily line up with when the plants actually need them.

"That initial delay is important, because when you sow a crop, the seed takes some time to germinate and grow, and the plant doesn't actually need the nutrients immediately," explains McLaughlin. "So if you can engineer a 10 to 30 day delay, depending on crop and environment, that's probably going to give the crop a better chance of catching the nutrients."

In their tests, the researchers loaded micronutrients of zinc and copper onto sheets of graphene oxide, and administered them to wheat, along with control groups of conventional soluble fertilisers. While there was the expected initial burst of nutrients administered within the first day, the graphene-based fertilisers retained more for a slower release, and sure enough, those wheat crops were found to have a higher uptake of zinc and copper.

While there might be some environmental concerns about adding more carbon to the soil, the structure of graphene is relatively close to that of organic carbon already found there. There's even a chance it may even be beneficial, breaking down into another kind of nutrient.

"Graphene isn't particularly different to soil organic matter," says McLaughlin. "In actual fact with degradation studies with graphene in the environment, it looks as if it degrades to humic acids, which are regarded as quite beneficial in agricultural systems."

Further studies into the graphene oxide-based fertilizers are looking to work with macronutrients like phosphate and nitrogen, as well as modifying the surface properties of graphene to release nutrients even slower. Early results have been promising, and fertiliser producer The Mosaic Company already has an option to license the technology.