DIVISION S-8—NUTRIENT MANAGEMENT & SOIL & PLANT ANALYSIS Comparison of Methods for Interpolating Soil Properties Using Limited Data

ABSTRACT pendence between measurements at different locations. Methods currently in use include kriging, inverse-dis-Spatial interpolation methods are frequently used to characterize tance weighting, and thin-plate smoothing splines, andpatterns in soil properties over various spatial scales provided that the data are abundant and spatially dependent. Establishing these one can use numerous approaches with each of these criteria involved comparisons of abundant data from many fine-scaled (see Journel and Huijbregts, 1978; Cliff and Ord, 1981; (,100 ha) investigations. In this study we investigated whether it was Isaaks and Srivastava, 1989; Watson, 1992; Cressie, appropriate to use spatial interpolation methods with limited (n 5 1993). There is some debate, however, as to which is 46), coarse-scaled (1188 ha) soils data from a Vertisol plain. Methods the best or most appropriate method (Voltz and Web-investigated included ordinary kriging, inverse-distance weighting, ster, 1990; Laslett, 1994; Hosseini et al., 1994; Wollen-and thin-plate smoothing splines with tensions. Comparison was based haupt et al., 1994; Gotway et al., 1996).on accuracy and effectiveness measures, and analyzed using ANOVA Use of any spatial interpolation method is currentlyand pairwise comparison t-tests. Results indicated that spatial interpo-based on a minimum sample size or pairwise comparisonlation was appropriate when the data exhibited smooth and consistent criterion and certain characteristics of the data (Journelpatterns of spatial dependency within the study area and the selected ranges of estimation and weighting used in this investigation. Nine and Huijbregts, 1978; Isaaks and Srivastava, 1989). Th