Recent developments in cosmic ray soil moisture observing system in Slovenia

Reliable soil moisture observations are pivotal for informing sustainable agricultural decisions under an ongoing changing climate. A cosmic-ray soil moisture observing system (SI-COSMOS) network was established for the period 2025-2040 to enhance soil moisture monitoring in Slovenia. The rationale was based on extensive experience with point soil moisture sensors in operational decision-making at the farm level, where they proved highly vulnerable to damage from land operations and wildlife activity. At the same time, the information was limited to micro-local conditions. As an alternative, a less vulnerable, non-invasive, intermediate soil-moisture network was established. As of Jan 2026, the network consists of 14 cosmic ray neutron sensors (CRNS). In this contribution, we present the network architecture, current calibration experiences, and discuss the network's role in the national and international context.

SI-COSMOS locations spread across the Continental, Alpine, Karst, Mediterranean, and Pannonian regions. Installed are lithium fluoride and boron carbide-based CRNS. The network's elevation ranges from 10 m to 500 m above sea level. Land use at locations includes olive groves (3), grasslands and pastures (2), hop plantations (2), mixed land-use systems (6), and forest (1), mainly under rainfed, but also irrigated (drip, drum, and pivot) conditions. Soil moisture is captured in various soil types.

At the national scale, the vision of SI-COSMOS is to support investigating soil–water-plant–atmosphere interactions under diverse climate, land-use, and soil conditions, to support improved drought detection and management, as well as hydrological modelling and applications. Additionally, the network aims to further develop and validate surface soil moisture products based on remote sensing or modelled data, for improved large-scale soil moisture observations at the national and international scales. Products based on SI-COSMOS will support development of transferable real-time land management tools for enhanced water resilience.

Acknowledgements: This research was funded by the Slovenian Research Agency (ARRS) with a grant to the Ph.D. students Nejc Golob and Špela Srdoč, and partially supported by research programme P4-0085, national targeted research project (V4-2406), Interreg Alpine Space program, project Alpine Space Drought Prediction (A-DROP) (grant number 101147797), European Union – LIFE Programme (LIFE23-IPC-SI-LIFE4ADAPT), OPTAIN Horizon 2020 (grant number 862756), the NextGenerationEU project ULTRA 4. Sustainable Environment, and the Slovenian CAP Strategic Plan 2023–2027.