By Alice McFarlane

Finetuning fertilizers for better crop yields

Nov 20, 2024 | 3:39 PM

Many agricultural soils are deficient in the nutrient zinc despite the fact that farmers use fertilizers enriched with the element.

This limits crop yields and reduces food quality. It’s estimated that roughly a third of the global population consume foods low in zinc, which can increase sickness and death in early childhood, as well as impaired growth and cognition.

Using the Canadian Light Source (CLS) at the University of Saskatchewan (USask), researchers from the University of Adelaide in Australia investigated how to manufacture more efficient zinc-enriched fertilizers.

The HXMA beamline at CLS was used by researchers to examine at the molecular level what happens to the water solubility of zinc which is its ability to dissolve in water when it’s added to ammonium phosphate fertilizer.

University of Adelaide spokesperson Dr. Rodrigo da Silva said going in to the project, the group thought the type of zinc compound would be a good predictor of a fertilizer’s solubility.

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“However, the CLS beamline enabled us to understand that the agronomic performance cannot be predicted based on what form of zinc is present in the fertilizer granules,” da Silva said. “Instead, the pH drives the fertilizer zinc solubility and availability to the crops.”

Dr. da Silva and colleagues found that when zinc is added to phosphate fertilizer it forms a range of different zinc phosphate compounds. However, its solubility was not related to the relative abundance of these compounds, but to fertilizer pH.

This means that zinc added to more alkaline phosphate fertilizers such as diammonium phosphate will have very low solubility and hence low agronomic effectiveness for crop uptake.

The University of Adelaide team found that lowering fertilizer pH by spraying the granules with an acid solution further increases the solubility and availability of zinc compared to current commercial products.

The researchers also showed an additional method to increase Zn water solubility by putting a barrier coating on fertilizer granules, to separate the zinc from the phosphate. They showed that there was more uptake of zinc by plants treated with the barrier-coating fertilizer.

The Mosaic Company, the world’s leading producer of concentrated phosphate and potash, funded the research and has patented both technologies in conjunction with the University of Adelaide’s Fertilizer Technology Research Centre.

“It is crucial to improve zinc fertilization practices, to maximize yields and produce more nutritional food,” da Silva said. “This research can help the industry produce more efficient fertilizers.”

The findings were published in the Soil Science Society of America Journal.

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alice.mcfarlane@pattisonmedia.com

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