Spatial variations in soil fertility can obscure treatment effects and hence lead to incorrect fertilizer recommendations. This study was aimed at evaluating oil palm growth response to K application. The response variable in this study was plant growth, expressed as plant height and leaf length. Treatment effects on plant height and leaf length were investigated using Analysis Of Variance (AOV). Both growth variables were assessed for spatial structure using variography. This was followed by Nearest-Neighbor Analysis (NNA) to derive adjusted growth data. The NNA involved a 3-step procedure carried out in an iterative fashion. Treatment effects on the NNA-adjusted growth data were examined using AOV and compared with those obtained using the original growth measurements. Results showed that before removing spatial trends, the effect of treatments on plant growth were not significant. Growth variables exhibited a significant spatial trend. A corresponding observation was found for growth residuals. The NNA technique was found to substantially reduce structural variance present in the growth data sets, which enabled the assessment of true treatment effects. Following the NNA adjustment, growth variables varied significantly among treatments with the untreated control giving the highest increase in plant growth. The NNA adjustment also rendered improved precision to the linear model, computed using AOV.
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