Soil Salinity Impact on Phosphorus Forms of Some Soils of El-Dakhla Oasis, Egypt

: Nine surface (0-30 cm) soil samples were collected based on their salinity levels from El-Dakhla oasis, New Valley, Egypt to investigate the effect of soil salinity level on phosphorus (P) forms. The soil samples were divided into two levels based on their content of soil salinity to non-saline samples (ECe<4dS/m) and saline ones (ECe>4 dS/m). Seven fractions of soil P (resin-P, NaHCO3-Pi, NaHCO3-Po, NaOH-Pi, NaOH-Po, HCl-P and Residual-P) were sequentially extracted from each soil sample using the modified Hedley method. The results indicated that relative to the total P, the mean percentages of resin-P, NaHCO3-Pi, NaOH-Pi, NaOH-Po and residual-P fractions were higher in the saline soil samples (ECe>4 dS/m) than those of the non-saline ones (ECe<4dS/m). On the other side, the mean level of HCl-P fraction was lower in the saline soil samples. So, soil salinity tends to motivate levels of labile P (resin-P, NaHCO3-Pi, NaHCO3-Po), NaOH-Po and residual-P to increase on the charge of reducing the HCl-P level. Significant positive correlations were recorded between the NaHCO3-Pi, NaOH-Pi and NaOH-Po fractions and the ECe, Ca+2, Mg+2, Na+, HCO3-, Cl-, SO4-2 and SARe of these soil samples. However, the NaHCO3-Po, HCl-P and residual P fractions were negatively correlated to the ECe, Na+, Cl- and SARe