Determination of management zones for a tobacco field based on soil fertility

Present nutrient management recommendations for flue-cured tobacco (Nicotiana tabacum) in Central China are typically uniform for large regions. This results in over-application in areas with high nutrient levels and under-application in areas with low nutrient levels. An 87-ha tobacco field was selected to define management zones (MZs) for more precise soil nutrient management. Our objectives were to: (1) quantify the spatial variability of soil fertility variables, and (2) delineate the MZs by the combined usage of principal component analysis (PCA) and fuzzy cluster algorithm. To achieve these objectives, soil samples (0–20 cm) were taken from 81 points on an approximately 100-m grid in March 2007. Soil samples were analyzed for pH, organic matter (OM), total nitrogen (TN), alkalytic nitrogen (AN), available phosphorous (AP), available potassium (AK), and cation exchange capacity (CEC). Spatial variability was assessed and spatial distribution maps constructed using geostatistical techniques. PCA and fuzzy cluster algorithm were then performed to delineate MZs; fuzzy performance index (FPI) and normalized classification entropy (NCE) were used to determine the optimum cluster number. Results showed that the optimum number of MZs for this study area was three and analysis of variance indicated the heterogeneity of soil fertility among different MZs. The defined MZs provide a basis of information for site-specific fertilizer management in the tobacco-planted field.