Designing sampling grids from imprecise information on soil variability, an approach based on the fuzzy kriging variance

It is shown how, given a fuzzy formulation of the variogram of a soil prope rty, a fuzzy set of grid spacings that will achieve a target kriging varian ce can be derived. This fuzzy set of grid spacings can then be defuzzified in a more or less conservative way to define a sampling scheme. The method is illustrated in three examples. The first uses a hypothetical fuzzy vario gram. The second is a fuzzy variogram for topsoil organic carbon content in a field, based on the crisp variogram of a related ancillary variable and generalized information on topsoil variability at field scares. The third f uzzy variogram is for topsoil pH, assuming no local knowledge but represent ing in fuzzy form the range of variability in a collection of variograms fo r this property in the soil science literature. (C) 2000 Elsevier Science B .V. All rights reserved.