Model-based approach for measurement of basic soil nutrient Tsvetelina Georgieva, Stanislav Penchev, Nadezhda Paskova, Eleonora Nedelcheva and Plamen Daskalov E3S Web Conf., 638 (2025) 03001 Published online: 16 July 2025 DOI: 10.1051/e3sconf/202563803001