A GEOSTATISTICAL METHOD FOR SOIL-SALINITY SAMPLE SITE SPACING

A calibrated Four-Electrode Probe (FEP) was used for inexpensive and i ndirect determinations of salinity-sensor Electrical Conductivity (EC) in a plot at Cauto Valley, Cuba. Two transects were made in the North -South (N-S) and East-West (E-W) directions. Laboratory measurements o f soil EC were also made from samples taken on a 50-m spaced square gr id. A linear semivariogram was obtained for the salinity-sensor EC mea surements at the E-W transect, which agrees with the topographical slo pe of the plot and with the expected soil salinity variation. It also coincides with the spatial structure of laboratory-measured soil EC. A cross-validation analysis has shown that EC semivariograms obtained f rom FEP measurements can characterize the soil EC spatial variation in a similar way as semivariograms of laboratory-measured soil EC. Thus, the distance between samples for soil salinity maps can be based on t he semivariogram's range of salinity-sensor EC measurements. (C) 1998 Elsevier Science B.V. All rights reserved.