Table 171

Mean values of the discriminant variables Selected by Stepwise discriminant procedure (P = 0.15) for the Three Soil drainage Classes

Soil drainage distance to drain Slope deep EC Class (m) (degree) (mS/m)

MWD 125 1.45 34.0

SWPD/PD 37 1.05 49.5

topography and topography plus electrical conductivity data. Separation of WD and MWD classes was less successful due to the above-mentioned insignificant differences between slope and deep EC values corresponding to WD and MWD drainage classes. Discriminant analysis with topography and EC slightly improved the estimation accuracy comparing with topography only due to better separation of WD and MWD drainage classes.

Cross-validation results of indicator kriging were not as accurate as those from discriminant analysis. Indicator kriging correctly estimated drainage classes at only 56 percent of the sites comparing with more than 60 percent of correct estimations from discriminant analysis. Better results were obtained when information on spatial variability of drainage class data was supplemented by the topographical data in the cokriging procedure. Indicator cokriging with slope and distance to drainageway produced the most accurate drainage class prediction comparing with the other methods (Table 17.2).

The most substantial difference between discriminant analysis and kriging and cokriging for creating maps pertains to the fact that kriging and cokriging procedures are exact estimators, and

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