Thirty-four soil samples were collected from Garb El-Mawhob soils, northwest of El-Dakhla oasis, New Valley governorate, Egypt to evaluate the soil available phosphorus and its relation with the properties of these soils. These samples were taken from the surface (0-30 cm) and subsurface layers (30- 60 cm) of 17 soil profiles covered the study area. Most of the soil samples had a texture of loamy sand, sandy clay loam and clay. In most cases, the studied soils showed mild alkaline pH (7.4 to 7.8) values. The electrical conductively (ECe) and CaCO3 of these soils varied from low to high levels and ranged from 1.05 to 163 dS/m and from 2.2 to 57.58%, respectively. The soil organic matter content differed from 0.08 to 2.27%. Also, the soluble cations and anions in most of the studied soils followed the order of Ca+2 >Na+> Mg+2 > K+ and Cl- > SO4= > HCO3-, respectively. The cation exchange capacity (CEC) and sodium adsorption ratio (SARe) of these soils were ranged from 6.58 to 57.49 cmolcÅ/kg and from 0.11 to 45.18%, respectively.
The NaHCO3-extractable soil phosphorus of these soils varied from 2.25 to 65.35 mg/kg in the surface layer and from 3.34 to 24.49 mg/kg in the subsurface one. In general, about 50% of the studied soil samples had a low level of available P (< 6 mg/kg), 24% of them showed a medium level (6 -10 mg/kg) and 26% of them contained a high level of available P (>10 mg/kg). Moreover, the studied soil samples that had clay and clay loam textures contained a high level of available P than those having other textures. The available P showed highly significant positively correlation, with some soil properties, such as OM, HCO3-, CEC and silt contents, while it was negatively correlated with ECe, Na+,CaCO3 and Ca+2.