Effect of Shape, Size of Pores on Saturated Hydraulic Conductivity of Some Iraqi Soils

A. S. Ati, B. M. Kareem
Dep. of Soil Science and Water Resources, University of Baghdad-College of Agriculture,Baghdad

This study aims to find out the effect of shape, size of pores on saturated
hydraulic conductivity. Ten pedons were selected from the north of Iraq; five pedons
were selected from Sulamani province: Bakhteari forest, Bazian, Choesoor, Kanakow
and Sarsank was from Duhok province. While in the middle sites, five pedons were
selected from Baghdad, two from college of agriculture, Al-Tarmia, and Al-Raeed
experimental station, the last pedon from Al-Anbar province – Al-Husaenia. Disturbed
and undisturbed soil samples were taken from surface and subsurface horizons from
each pedon. Some chemical and physical properties were determined, which include
texture, carbonate minerals, free iron oxides, organic matter, bulk density, porosity and
hydraulic conductivity. Also they were used for micro morphological characterization as
thin section and scanning electron microscopy. The results indicated that the highest
value of saturated hydraulic conductivity of the northern sites were 77.73cm.hr-1
at P4A1(north), the lowest value was 0.47 and 0.47 cm.hr-1 observed in surface and subsurface
horizons of P3 . The high value of middle sites was 9.89 cm.hr-1in P9A1; the lowest value
was 0.89 cm.hr-1 in P8C1. Micro morphological characterization showed variation in the
shapes and size of pores for all studied horizons. Also, they showed coating and filling
material affecting the pores. The dominant shapes were channels, chambers, voids. The
results show that there are differences in shapes and size of pores between north and
middle sites, where the dominant shapes of pores in middle sites were chamber and
packing. The results showed the existence of free iron oxides which increased MWD and
bulk density and decrease hydraulic conductivity and porosity; also it's forming type of
shape as small chamber. Organic matter forms meta vughs which make the hydraulic
conductivity high because this type of shape is more stable.

Keywords: hydraulic conductivity; shape and size of pores; micro morphological; scanning
electron microscopy


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