This study addresses the technology of soil sampling of agricultural fields which are inherently variable in both space and time. Spatial variability of soil saturated hydraulic coductivity(K) and the salinity(EC) of the soil was studied in an eleven hectare field. This field was divided into two sections by a drainage canal. These sections are: The western section(site 1) and the Eastern section (site 2).
Measurement of K was made on both sites in the two vertical directions,on a line, at 25 meter intervals and the depth of 50 centimeters. Studies on EC was also made on both sites on two vertical directions of 25 meter intervals, at three depths of 0—20,20—50 and 50—100 centimeters. To determine the spacial variations and co1clusively finding the optimal interval of soil sampling for these physical and chemical characteristics of the soil in the sites under consideration, the semivariance, which is a statistical function for the spatial variation analysis of the geographical variables, was used. The results of this experiment showed that at site 1 hydraulic conductivity measurements of 100 and 50 meters were suficient for North-South and East-West directions, respectively. The results also indicated that at site 2 sampling intervals for EC determination were 125 and 100 meters for East-West directions, respectively. The semivariograms show that at lower depths (20-50 and 50 to 100 centimeters) the situation is somewhat different, so that there is not any continuity and dependence between the samples taken for EC determination for. depth 50—100 meter(nugget effect). Onsite2, at North-south direction with aforesaid three depths, the EC had no connection with the interval. At its vertical djrection(East-West), at the depth of 0-20 cm, the 50 meters interval and at the depth of 20-50 cm the 75 meters were specified for the degree of salinity variation.
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