Carbon Sequestration in Soils of Agricultural Landscapes (Carbon SeAL) – The Potential of Phytoliths Originating from Crop Straw

• Applicant: Dr. Daniel Puppe
• Subject Area: Soil Sciences
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 568397851

Silicon (Si) uptake has been found to increase the resistance of crops against stressors like drought or fungal infections. However, annual crop harvesting results in large exports of Si from agricultural fields (anthropogenic desilication) - usually without compensation and with severe consequences for crop resilience. The applicant showed that up to 60% of Si exports can be avoided by crop straw recycling over decades. Crop straw recycling is thus a potential key practice for managing Si supply in a sustainable crop production. In the requested project biogenic silica (SiO2∙nH2O), the so-called phytoliths, formed in different cereal crop species will be subject to intensive investigation using a combination of state-of-the-art microscopic and spectroscopic methods. As phytoliths can persist in soils for centuries to millennia, the storage of phytolith occluded carbon (PhytOC) might be a promising method for sequestering carbon as a contribution to climate change mitigation. In this context, it is of great importance to determine the cell-wall-to-lumen-phytolith-ratios in different cereal crop species, because these different phytoliths show different carbon contents: While cell wall phytoliths are characterized by relatively high carbon contents, lumen phytoliths are characterized by relatively low carbon contents. To evaluate the potential of these different phytoliths for carbon sequestration in agricultural soils, long-term field experiments (quantification of phytolith carbon storage in agricultural soils), greenhouse experiments (analysis of cell-wall-to-lumen-phytolith-ratios in different cereal crop species and crop organs in relation to water and Si availability), and laboratory experiments (examination of phytolith dissolution kinetics in relation to physicochemical phytolith surface properties) will be combined in the requested project. The objectives of the requested project are (i) to evaluate the potential of cell wall and lumen phytoliths for C sequestration in agricultural soils, (ii) to better understand silicification and the effects of anthropogenic desilication and drought stress on phytolith formation in cereal crops, and (iii) to derive practice-oriented recommendations for the implementation of cereal crop straw recycling in a modern, sustainable production of resilient crops. The results of project "Carbon SeAL" will be crucial for the solution of global societal challenges such as climate change and food security, because they will allow a much more reliable estimation of (global) PhytOC pools and provide the requisite know-how for enhancing the resilience and climate adaptability of cereal crop species in future agricultural plant-soil systems.

• DFG Programme: Research Grants