In Garb El-Mawhob area, northwest of El-Dakhla Oasis, New Valley governorate,
Egypt, nine transects (≈ 5km away between two consecutive ones) containing
17 soil sites were designated to evaluate the available potassium (K)and
its relation with some soil properties. Surface (0-30) and subsurface (30-60) soil
samples were collected from each profile, air-dried, ground, sieved and then, kept
for some physical and chemical analyses.
The obtained results indicated that about 56, 65 and 41% of the total soil
samples contained sand, silt and clay respectively of more than 60, 10 and 30%,
respectively. The saturation percentage (SP) varied from 25 to 110% and increased
whenever the clay or organic matter content increased. The organic matter
content differed from 0.01 to 2.48 % and decreased with soil depth. The
CaCO3 content of these soils varied from 2.20 to 59.24%. The pH values ranged
from 7.44 to 8.03.The electrical conductivity of the soil paste extract (ECe) differed
from 0.71 to 171.30 dS/ m with an average value of 20.33dS/ m. The soluble
anions could be arranged in the descending order of Cl> SO4 > HCO3. The
soluble cations could be arranged in the descending order of Na >Ca> Mg > K .
The sodium adsorption ratio of the soil paste extract (SARe) ranged from 0.31 to
85.20. Cation exchange capacity (CEC) values ranged from 6.58 to 62.56
cmol(+)/ kg with a mean value of 29.44 cmol(+)/ kg and it increased with soil
depth.
The available K ranged from 148.98 to 944.12 mg/ kg with an average
value of 451.81 mg/ kg. About 47.06% of the studied soil samples contained a
very high level of available K (> 450 mg/ kg),20.56% had a high K level (251-
450 mg/ kg), 29.41% showed a moderate K level (151-250 mg/kg) and only
2.94% exhibited a low K level (86-150 mg/ kg). The available K was found to be
positively correlated to silt content, clay content, SP, ECe, SARe and CEC as well
as soluble Na, Mg, HCO3 and SO4. However, it was negatively correlated to both
sand and CaCO3 contents.