Tracing copper and zinc in organic soil-crop systems by 65Cu and 67Zn labelling

• Applicants: Professor Dr. Moritz Bigalke; Kai Nils Nitzsche, Ph.D.
• Subject Area: Soil Sciences
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 564742762

Manure and copper-based fungicides are known sources of copper (Cu) and zinc (Zn) in agriculture and their long-time application can cause an accumulation of these metals in agricultural soils. While Cu and Zn are essential micronutrients to plants, animals and humans, elevated Cu and Zn concentrations can pose environmental risks to biota and affect soil fertility. For maintaining sustainable and fertile soils, a precise understanding of the Cu and Zn sources, their fate in soils, and their potential bioavailability is necessary. The overarching objective of the proposed project is to contribute to the sustainable trace metal management and maintain soil fertility and crop quality in organic farming. Specifically, we aim to answer the following research questions: (1) What is the soil accumulation, cycling and long-time availability of Cu from Cu-based fungicides and from slurry in realistic crop rotations? (2) What is the accumulation, cycling and long-time availability of Zn form slurry, and what is the contribution to the Zn pool in the edible parts of different crops relevant for human consumption? We will conduct two field experiments on a Luvisol using cutting-edge stable isotope labelling of Cu-based fungicides and animal manure. Both experiments will be run in parallel. In the first experiment, a 65Cu-labelled Cu-based fungicide will be applied on potato (Solanum tuberosum) equivalent to the maximum permitted Cu mass of 3 kg ha-1 in organic farming in Germany. The follow crop will be winter wheat (Triticum aestivum). In the second experiment, a 65Cu-67Zn-labelled pig slurry will be applied on winter wheat. Afterwards, a mixture of catch crops and then by broad bean (Vicia faba) will be cultivated following an established crop rotation. The Cu and Zn concentrations and the occurrence of the isotope spike in soil solutions, in plant biomass, and in operationally defined soil fractions will be analysed via ICP-MS, which allows for precisely calculating the Cu and Zn contributions from the fungicide and manure applications to the respective compartments. Consequently, the outcomes of the proposed research will allow for directly tracing the fate of Cu and Zn in the soil and for assessing the uptake into up to three generations of crops of a common crop rotation. Thus, our study will help to better assess the environmental fate of Cu and Zn in organic agriculture.

• DFG Programme: Research Grants