Slow-release farming: making crop chemicals last longer
Farmers rely on herbicides and other crop chemicals, but these can be lost through evaporation or washed away by rain. That can mean repeat spraying, higher costs and more chemicals in the wider environment.
The idea: release it slowly
Controlled release is a familiar idea in medicine, where a tablet can deliver its drug gradually. We are exploring the same idea for agriculture by storing active chemicals inside the tiny pores of metal-organic frameworks (MOFs), which then release them over time.
Keeping herbicides under control
In one study, we worked with iron-based MOFs, chosen for their low toxicity and low cost. We loaded them with two common herbicides, 2,4-D and MCPA. The best version held up to about 27% of its weight in herbicide.
MOFs are usually fine powders, which are awkward to apply in the field. We therefore combined them with PCL, a biodegradable polymer, to make them easier and safer to handle. Over nine days of testing in water, the version with an added amine group released its herbicide more slowly and steadily.
Pheromones too
During my PhD, I also studied zirconium-based MOFs for delivering 3-octanone, a pheromone. Laboratory measurements confirmed that the molecule could be loaded into the materials. Computer simulations then helped us to understand how it interacts with the framework and moves through its pores.
Why it matters
Slow-release materials could mean fewer applications and less chemical lost to the environment. These results come from the laboratory, so soil and field trials, along with cost studies, would be needed to show the real benefit for farmers.
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