Nine years of AMAIZE-P: When the international research training group concludes in 2027, more than 40 PhD students and postdocs on the German side and more than 50 on the Chinese side will have been trained as experts in the field of resource-efficient phosphate utilization. To date, almost 100 publications in peer-reviewed journals already attest to the high-caliber qualifications obtained at the two top universities.

"All PhD students and postdocs at the University of Hohenheim have at least one tandem partner at the CAU," explained Prof. Dr. Torsten Müller, spokesperson for the German side. "In the new funding period, the third group will start. It will be expanded compared to the first two by one additional PhD student each from Germany and China." These students will also add to the graduate program by examining the market economy aspect of the topic.

Global phosphate shortage threatens food security

The war in Ukraine has given the issue additional significance. "The war is making fertilizer scarce and expensive. Global food security is more at risk than ever," Prof. Dr. Müller stated. "In addition, phosphate deposits are limited, so it is possible that prices for this increasingly scarce resource will increase greatly in the coming decades."

China is currently still focusing on mining areas in its own country, but these will be exhausted in about 35 years. "This also has consequences for the global market. If Chinese agriculture imports its phosphate in the future, that will also drive up prices."

On the one hand, phosphorus is irreplaceable as a scarce but essential nutrient element. On the other hand, environmental problems often occur in areas with high livestock density because too much phosphate is spread on the fields there via farm manure, especially slurry. AMAIZE-P is looking for solutions to this complex global problem using maize production systems as an example. The objective is to create a sustainable circular economy in line with the principles of the bioeconomy.

“Research conducted in Germany and China at the same time is the perfect complement," said Prof. Dr. Müller, explaining the approach. "In Germany, larger farms dominate, while Chinese agriculture is still mostly small-scale. The climate conditions of the two countries are also very different. This means that together we can cover almost all production systems that play a role worldwide."

Strategies for more efficient phosphate use

In field trials, the researchers compare different fertilization strategies and crop rotations in terms of their effect on phosphate availability in the soil. "We can already state, for example, that recycled phosphate fertilizer is capable of replacing mineral phosphate fertilizer," Prof. Dr. Müller said when discussing the interim results. "We are also currently investigating whether legumes increase phosphate availability to maize in rotation or when grown simultaneously in the same field."

The researchers are also focusing on genetic aspects: For example, genetic differences in phosphate use efficiency were found in modern and traditional maize varieties. In the future, this can serve as a basis for breeding new maize varieties that can use the nutrient more efficiently.

The researchers also use drone flights and three-dimensional simulations of maize plants to determine the exact nutrient requirements in individual subplots. This allows them to apply the fertilizer only where it is really needed.

Circular economy conserves resources

To achieve a circular economy, the researchers also have an eye on the further path of phosphate: They are investigating how phytate content in maize and thus in feed affects chickens and pigs, as phytate is the main phosphorus storage form in plants. "The interaction of microorganisms in the animals' digestive tract plays a particularly important role here," stated Prof. Dr. Müller.

To close the loop, waste and residual materials are also being reassessed: "Phosphorus-containing biomass can be converted via a technical process known as hydrothermal conversion (HTC)," said the research training group spokesperson. In a pilot plant, a biorefinery in the Swabian Alb, new carbon materials are being produced, for example for electrodes. On the other hand, work is being done on recovering the phosphorus as the mineral fertilizer struvite, which in turn can be used in crop production.

Objective: Recommendations for action for politics and society

Ultimately, the researchers would like to derive recommendations for policy and agricultural practice for the efficient management of phosphate. "To do this, we are simulating how a shortage of phosphate will affect agricultural and food markets," said Prof. Dr. Müller. “That way we can assess what the implications are for global food security."

By modeling different future scenarios, they compare the efficiency of phosphate fertilizer use. This allows for an analysis of how different land use systems affect Germany and China economically and ecologically.