Soil variability within agricultural fields is rarely captured by conventional management, which applies inputs uniformly regardless of underlying spatial heterogeneity. This exploratory study evaluated whether freely available Sentinel-2 multispectral imagery, processed through Fuzzy C-Means (FCM) clustering in an open-source GIS environment, can support preliminary management-zone delineation in a small Mediterranean alfalfa field and whether targeted soil sampling can provide site-specific ground-truth evidence for the resulting zones. A Sentinel-2 Level-2A Bottom-of-Atmosphere (BOA) image acquired on 26 April 2022 from tile T34SDJ during peak alfalfa canopy development was used to calculate four spectral indices: Normalized Difference Vegetation Index (NDVI), Soil Adjusted Vegetation Index (SAVI), Enhanced Vegetation Index (EVI), and Normalized Difference Water Index (NDWI). These indices were standardized prior to clustering and synthesized through FCM to delineate management zones within a field of 8 ha in Etoloakarnania, western Greece. Six georeferenced composite soil samples were then collected from locations within the mapped zones to provide preliminary validation of the spectral zones. The two zones showed strong directional differences in several soil fertility indicators. Available phosphorus differed by a factor of 6.5 between zones (62.0 vs. 9.45 mg kg−1), with a localized high-value point reaching 110 mg kg−1 within the higher-fertility zone. Exchangeable potassium followed the same pattern (0.71 vs. 0.28 meq 100 g−1). DTPA-extractable iron differed three-fold (112.0 vs. 37.37 mg kg−1) and zinc nearly five-fold (2.79 vs. 0.56 mg kg−1), while pH was virtually identical across zones (6.15–6.20). These results suggest that, in this site-specific case, the combination of Sentinel-2 indices and FCM clustering produced spatial zones that were broadly consistent with measured soil-fertility contrasts. However, because the validation dataset consisted of only six composite soil samples and because sample-level FCM membership scores, spectral-index values, and formal cluster-validity diagnostics were not retained from the original workflow, the findings should be interpreted as an exploratory screening exercise rather than as a validated decision-support tool. Further soil sampling, yield or biomass monitoring, multi-season assessment, formal cluster diagnostics, and local fertilizer-threshold evaluation are required before operational nutrient prescriptions are implemented.