Soil samples were collected during the season of summer of 2011, from different locations of unused soil, in the western Iraqi desert. Soil samples conducted analyzes of soil taken from the horizons of the soil to investigating the depth of 30 cm. Soil sample passed through 8 and 4 mm sieves respectively, with natural moisture then air dried, took the soil aggregate on the sieve of 4 mm for the purpose of estimate the mean weight diameter(MWD).
The results showed that the MWD Scattered with the soil characteristics, and shows the regression analysis that the characteristics of the soil in general do not give a significant correlation for each properties individually with MWD. The correlation is significant exponential decrease with the clay percentage when pre-wetting samples by flood with r2 equal 0.31, and logarithmic decrease with pre-wetting by steam and under 10 cm tension with r2 about 0.35 and 0, 18. Significant exponential increase to MWD with increasing the percentage of gypsum in soil sizes 0.25 – 0.5, but increase with power function with r2 0.47 for size less than 2 mm.
MWD was increased with increasing soil gypsum content, with exponential relations, for particles size less than 0.25 mm with r2 around 0.51. The overlap, shows that the values of the r2 increase with 0.30, 0.27 and 0.20 for group soil separate and groups the physical and chemical properties respectively, to 0.65 when overlapping groups properties as average for all pre-wetted method, and gave the groups overlap ratios of lime, gypsum and organic matter r2 equal to 1.00, as well as when overlapping each studied properties, with different input regression analysis.