Spatial Variability and Management Zones: Leveraging Geostatistics and Fuzzy Clustering

Abstract Purpose: Soil degradation, exacerbated by agricultural practices that ignore soil spatial variability is a critical threat to sustainable agriculture and food security. Management zones (MZs) delineation is a promising approach that has been used to manage soil spatial variability, and tailored agronomic inputs to optimize crop yield while mitigating soil degradation. Methods: The research was conducted in a 3530 km 2 catchment located within the Mashhad Plain of Northeast Iran, where arid climate conditions are dominant. Soil physicochemical properties such as texture, bulk density, pH, electrical conductivity (EC), organic carbon, (SOC), cation exchange capacity (CEC), total nitrogen (N), available phosphorous (P), potassium (K), and micronutrients were analysed for 48 samples from the catchment and computed Principal Component Analysis (PCA), ordinary kriging (OK), and fuzzy k-means clustering. Results: Physicochemical properties of the soil samples showed high (nugget/sill (N/S)<0.25), to moderate spatial autocorrelation (N/S< 0.75) except for pH (N/S>0.75). Cluster analysis partitioned the soil properties into two major groups, with PCA indicating that the first six components accounted for 82.9% of the total variance. We delineated seven distinct MZs associated with specific soil textures and elevations but not land uses. The delineated MZs can aid in implementing site-specific management practices, for instance, MZ 1 relatively requires more K fertilization and SOC amendments, while MZ 4 does not. MZs 5 and 6, with EC levels exceeding some cultivated crop tolerance, necessitate cultivating medium to high salt-tolerant crops, using low salt index fertilizers, and high-quality irrigation water. Conclusion: The study shows that management zone delineation can be used in sparsely sampled regions. Additionally, tailored practices can contribute to sustainable agriculture in the region, consequently, mitigating soil degradation and boosting crop productivity, ensuring soil health and food security for future generations. Graphical Abstract