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 Ca-
CO3 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 cmolc/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.