The potential of crop variety selection to enhance soil organic carbon stocks and yields: a soil-crop modelling study for spring barley in a Nordic climate

Crop breeding is attracting attention as a potentially effective strategy to enhance soil organic carbon (SOC) stocks, thereby mitigating climate change as well as improving soil physical health and the sustainability of arable cropping systems. We used the new soil-crop model USSF (Uppsala model of Soil Structure and Function) to investigate the potential of variety selection to increase SOC whilst maintaining or even improving yields in spring-sown barley under Nordic agro-environmental conditions. USSF combines a generic crop growth model with physics-based descriptions of soil heat and water flow and transpiration by plants, with a model of SOC turnover that considers the effects of physical protection and microbial priming on the rates of decomposition of SOC.Data on soil water contents, soil temperatures and above-ground biomass and grain yields were obtained during two growing seasons (2022 and 2023) in both drought and control treatments for two varieties of spring barley (“Annelie” and “Feedway”) grown on a loamy soil in Uppsala, Sweden. In 2022, above-ground biomass was not significantly different between the two varieties, whereas grain biomass was significantly larger in Feedway. No effect of the drought treatment on crop growth was detected for either variety. Crop growth was poorer in 2023, which was attributed to a colder spring and a drier summer. In this second year, Feedway had both larger above-ground biomass and grain yields than Annelie, and also showed a significant effect of the imposed drought treatment on both of these crop growth parameters, whereas Annelie did not.Eight crop parameters in USSF were treated as uncertain. Thirty “acceptable” parameter sets for each variety were identified by calibrating the model against the field measurements using the GLUE method. The USSF model could satisfactorily match the data in both drought and control treatments using a common parameterization. The results of this model calibration strongly suggested that the main difference between the two varieties of spring barley is that Feedway develops a deeper root system. This allowed for a better water supply, especially in the late summer drought period during grain-filling in 2023, leading to better crop growth, larger yields, harvest indices and return of crop residues.We are currently performing long-term (30-year) simulations for historical and future climates to evaluate the potential effects of cultivating these two varieties on SOC stocks and grain yields under contrasting weather and climatic conditions.