Effect of Sawdust Extract, Wetting and Drying Cycles on of Aggregates Soil Stability and Saturated Hydraulic Conductivity

A laboratory experiment was conducted, in the laboratories of the College of Agriculture-University of Anbar, for disturbed soil samples taken from one of the fields in the previous College of Agriculture, Baghdad University, latitude 33.2 south, and longitude 44.24 east. Wooden sawdust extract (WSE) was added to soil in 5, 10, and 15% levels in an equivalent proportion of soil organic matter (SOM) content for nine cycles of wetting-drying (WDC). A factorial three replications experimental design was statistically analyzed. A significant increase was noticed in the mean weighted diameter (MWD) of soil at fast wetting, where it raised for 5, 10, and 15% WDS levels. The interaction was significant in the second WDC for the same WSE levels in comparison with zero addition treatment where they were 123.62 and 173 % respectively, meanwhile 10 and 15 % WSE levels significantly superior to 5% level by 38 and 69 %. Whereas slow wetting MWD gradually to be 37 and 86% starting from third till ninth WDC successively compared to second WDC. The effect of WDCs on the saturated hydraulic conductivity (ks) of aggregates greater than 9.5mm was significant in this trait, as it increased by 13, 8, 13, 19, 18, and 18% for the 2ed, 4th, 6th, 7th, 8th, and last WDC, respectively. It also found a clear effect of the add-on levels in the saturated water conductivity (SWC) within 9.5 – 4 mm aggregates. There was a significant increase in equivalent add-on levels of 5, 10, and 15% with 8.4, 32.9, and 74.2% successively. There was a significant increase of 5, 10, and 15% equivalent addition levels of 8.4, 32.9, and 74.2% respectively compared to the level of non-addition of WSE extract. Soil samples tested with an electron scanning microscope, the samples to which WSE were added became granular and aggregated surfaces, while the untreated samples were smooth, with no granular surfaces and sharp edges.