Investigating the impact of warming on soil organic carbon pools and crop yields

Soil organic carbon (SOC) represents a major component of terrestrial carbon storage and plays a critical role in soil functioning and the global carbon cycle, regulating climate–carbon feedback. Quantifying the response of SOC pools to rising temperatures is essential for predicting soil–atmosphere carbon fluxes and sustaining agricultural productivity under future climate scenarios. This study investigated the effects of experimental warming (~ +2 °C) on SOC dynamics and crop yields within a soybean–sugar beet rotation system in northern Italy over two years (2023–2024). A randomized complete block design with open-top chambers (OTCs) was applied, and topsoil samples (0–20 cm) were physically fractionated into mineral-associated organic matter (MAOM) and particulate organic matter (POM). Carbon stocks and distribution, thermal and biological stability, were assessed using CHNS analysis, TGA-DSC, and incubation experiments. The induced warming generated crop-specific responses: SOC stocks decreased in soils cultivated with sugar beet (range: 1.4–5%) while they increased in those cultivated with soybeans (range: 3–6%), reflecting differences in root structure and residue inputs. MAOM/POM ratio decreased with warming in 2023 in all soils, while it increased in sugar beet soils in 2024, probably because of the rotation with soybeans. Thermal analysis revealed that warming and crop type significantly affected the thermal stability of SOC fractions. MAOM showed higher energy density than POM, confirming its greater stability. Crop specific responses were evident particularly in soybean, with reduced MAOM stability under warming, while sugar beet showed the highest MAOM thermal stability in both years. POM was more responsive to temperature increase, particularly in 2024, indicating enhanced vulnerability of labile SOC pools under warming. The cumulative CO2 values obtained from incubation tests (basal respiration) showed greater SOC lability in soybean soils. Yields have fallen dramatically as a result of warming (−70% for sugar beet and −80% for soybean) with estimated economic losses of approximately 3,000 and 1,000 €/ha, respectively. This highlights the need for integrated, evidence-based policies to steer the Common Agricultural Policy towards agricultural practices that protect SOC and ensure production security in the context of climate change.