Organic amendments reduce climate-induced cadmium accumulation in Spinacia oleracea L.

The application of organic substrates to agricultural soils is a key strategy in circular farm management, effectively improving soil quality by enhancing soil carbon and nitrogen stabilization, promoting soil microbiome diversity, and increasing resilience to environmental stressors. These amendments also exhibit strong metal-binding capacities through functional groups such as carboxylates, which is particularly advantageous for mitigating the mobility of harmful metals like cadmium (Cd)—a toxic element with no known metabolic role in plants or humans. Under future climate conditions, metals in soils are predicted to become increasingly mobile due to changes in soil biogeochemistry (Drabesch et al., 2024). This poses a significant risk to food safety, as demonstrated by elevated Cd concentrations in the edible tissues of spinach, a widely consumed leafy crop used as a model for metal uptake (Pienkowska et al., at EGU 2025). In this study, we evaluated whether amending soils with organic substrates could counteract the climate-driven increase in Cd mobility and accumulation during spinach cultivation. Six common organic amendments—farmyard manure, compost, humic substances, biochar, horn-bone-blood meal, and peat—were applied to an agricultural soil with a natural Cd concentration of 0.6 mg kg⁻¹. Spinach was grown under current and projected climate conditions for the year 2100 based on the IPCC SSP3-7 scenario. All amendments, except peat, significantly reduced Cd accumulation in spinach under future climate conditions, with manure and compost showing the greatest reduction potential. Mechanistic insights were gained through modeling Cd binding to fulvic acids (using WHAM VII) and assessing rhizobiome activity associated with metal mobilization and plant growth. These findings highlight the potential and elucidate the mechanisms by which organic substrates can enhance food safety under a changing climate by reducing the bioavailability of harmful metals.

 

References

Drabesch et al. (2024). Climate-induced microbiome alterations increase cadmium bioavailability in agricultural soils with pH below 7. Communications Earth & Environment.

Pienkowska et al., (2025). Climate change-induced cadmium accumulation in spinach. Abstract at EGU25-13116

IPCC (2021). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report.