Assessment of Spatial Variability of Soil Properties Using Different Methods to Identify Management Zones for Rotational Cropping Systems: A Case Study from Colombia
Site-|specific management for irrigation purpose remains a great challenge especially within mixed cropping system due to complex correlations and the spatial variability of soil properties. This variability generates crop yield heterogeneity within agricultural fields. This study was conducted in a 5-ha area cultivated in Inceptisols with rice-corn/cotton rotational cropping system in Tolima region-Colombia. The aim was to delineate field management zones (MZs) using three methods M1, M2 and M3, and evaluate their usefulness for a further site-specific management. Results were validated by comparing soil properties to rice/cotton and corn yield. Georeferenced soil samples were analyzed for soil texture, bulk density (BD), field capacity (FC), soil available water (AW), mesopores percentage (Mes), soil penetration resistance (PR), organic matter (OM), available phosphorus (P), and exchangeable bases content (Ca+Mg/K) ratio. Spatial variability of soil properties was analyzed with geostatistics approach. Further, spatial principal component (sPC), were performed to delineate the MZs using: M1- Fisher-Jenks algorithm with the first sPC, M2- Fuzzy k-means cluster analysis with two sPC, and M3- Fuzzy k-means with soil variables. The obtained MZs were effectively related to the rice-based cropping system yield. Results revealed that the optimum number of MZs depends on the aim of the investigation. Two MZs were recommended using M2 due to its lower fragmentation compared to other methodologies. This delineation could be suggested for fertilization management since Clay+Silt , OM, P, and Ca+Mg/K content differentiate when delineating one and two MZs. M2 provided also differences for AW, Mes, and PR when considering three MZs which can be used as a basis for irrigation site-specific management in precision agriculture.
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