Research team finds phosphorus recycled from waste materials is easier for plants to access
Researchers have uncovered new insights into how phosphorus from recycled materials moves through soil, offering guidance to support more sustainable fertilizer use.
Phosphorus is an essential nutrient for plant growth, yet many soils lack enough of it to support strong crop yields. Farmers often rely on fertilizers made from mined phosphorus – a limited, non-renewable resource.
As global agriculture shifts toward more sustainable practices, researchers are exploring alternative fertilizer recipes made from waste materials. These “recycled” ingredients include sewage sludge, leftover solids from water treatment; sewage sludge ash from when those leftovers are burned and meat and bone meal – bones and tissues which are not consumed.
Phosphorus research
In a recently published study, researchers from Denmark, Brazil, Germany, Lithuania and Switzerland used the Canadian Light Source (CLS) at the University of Saskatchewan to examine how phosphorus from these recycled fertilizers behaves in different soils over time.
The goal was to better understand when and where this phosphorus becomes available to plants – critical information for improving its effectiveness in agricultural settings.
The researchers used the CLS to identify the chemical forms and precise amounts of phosphorus present in both the fertilizers and soils.
“Phosphorus is one of the most difficult elements in the soil to analyze in a conventional lab,” says Aimée Schryer, lead author of the study and postdoctoral researcher at the University of Copenhagen. “It’s hard to make reliable conclusions or recommendations producers can use in the field based on those results. It’s more of a guess.”
“This is why using the synchrotron was so helpful. It allowed us to discover exactly what’s within our soils and in these recycled fertilizers so we’re much more confident with our conclusions,” Schryer adds.
Results and impact
The team found recycled phosphorus behaves differently than conventional mineral fertilizers.
While mineral phosphorus typically becomes less available over time, some recycled sources – particularly those derived from sewage sludge – became more available with time and moved further through the soil as time passed.
Having the recycled fertilizer move further through the soil is a significant advantage over mined fertilizer, which normally stays put, explains Schryer. More movement can make the fertilizer easier for plants to access.
The study also found soil type plays a significant role. Certain combinations of soil and recycled fertilizer improved phosphorus movement and availability, while others limited it, even under favorable conditions.
Overall, the results show a one-size-fits-all approach does not work when it comes to recycled fertilizers. Instead, farmers and researchers must consider both the type of soil and the timing of application to maximize effectiveness.
Using advanced tools at the CLS allowed the team to better understand the different forms of phosphorus present – information which is essential for making accurate predictions about how fertilizers will perform.
This research represents an important step toward reducing reliance on mined fertilizers and advancing a more circular agricultural system, where waste materials are reused productively.
Schryer says, while field studies are an important next step, her team’s findings will help inform future research and the development of practical recommendations for farmers.
Victoria Schramm is a communications coordinator for CLS, a national research facility based at the University of Saskatchewan in Saskatchewan, Canada. This article was originally published by CLS on June 9.
