Increasing temperature influence on soil organic carbon pools and on sugar beet and soybean yields: preliminary results

Soil organic carbon (SOC) plays a fundamental role in the global carbon (C) cycle and represents a key element of soil ecosystem services. Thus, the response of agricultural soils to global warming is important when assessing C accrual potential and soil fertility in a climate change scenario. In this research we investigate the influence of global warming on SOC pools, and on the yields of two crops, namely sugar beet (SB) and soybean (SOY). A temperature increase of ~2°C was simulated using Open Top Chambers (OTCs) in a randomized complete block design field experiment. Topsoil samples (0-15 cm) were collected from all plots before and after the experiment and characterized from the physical and chemical point of view. Particulate Organic Matter (POM) and Mineral Associated Organic Matter (MAOM) were also isolated. Data collected from sensors confirmed that soil and air temperatures inside the OTCs were higher than those outside the OTCs, both in the control and in the cultivated plots. In general, SOC in the MAOM fraction was 3-4× higher than in POM (76.4±2.4 vs. 20.2±4.5%) and showed a lower C/N value (8 vs. 12) suggesting a great contribution of microbial derived SOM. Following the experiment, the MAOM/POM ratio was quite different, suggesting an influence of increasing temperature on SOC distribution between pools (work in progress). Beside affecting SOC distribution between SOM pools, the 2°C temperature increase had also a strong impact on crop yields, with average values 3× (SB) and 5× (SOY) lower within the OTCs than those obtained outside the OTCs, corresponding to a loss of income of 1,000-3,000 €/ha.