In some soils, the relationship described by the USSL SAR-ESP model has been shown to vary in response to changes in ionic strength, clay mineralogy, and pH (Lieffering and McLay 1996; Kopittke et al.
From the same soils used to develop the SAR-ESP model, the USSL reported a similar relationship between PAR and exchangeable potassium percentage (EPP), which is described by the PAR-EPP model equation (Richards 1954):
it seems necessary to ascertain whether the widely accepted USSL SAR-ESP model is adequate in predicting sodicity hazard in soils irrigated with winery wastewater with high concentrations of both [K.
The data in our study were incorporated into the USSL SAR-ESP model, whereupon the curve of measured ESP had a greater asymptote relative to the curve of predicted values.
Again, predicted EPP provided by the USSL PAR-EPP model is also presented and is significantly (t(11)=9.
Similar observations were reported by Levy and Feigenbaum (1996), who reported an overestimation of ESP when using the USSL SAR--ESP model in a ternary Na-K--Ca system.
The results of the water samples were tabulated based on USSL classification (Table: 4).
According to USSL classification and Piper's trilinear diagram most of the samples fall under salinity condition.
Sodium Adsorption Ratio Effects Class 0-10 Excellent Low 10-18 Good Moderate 18-26 Fair Medium-High >26 Poor High Table 4: Classification of water samples based on USSL diagram .