Water content and organic matter are recognized as being important factors influencing soil compactibility. Sustaining soil organic carbon (SOC) is of primary importance in terms of improving the physical and mechanical properties of soils in arid and semi-arid regions. The pre-compaction stress and compression index obtained from Log (stress)-strain curve of a confined compression test are often used as criteria for determination of load support capacity and suseptibility to compaction of a soil. The objectives of the research reported here were to 1) characterize the soil physical properties and consistency limits (shirnkage limit, SL; plastic limit, PL;liguid limit, LL)and 2) obtain pre-compaction stress, compression index, cohesion and angle of internal friction of a silty clay loam soil under long-term (seven years) application of organic matters (compost, sewage sludge, farm yard manure) at three rates (25, 50 and 100 t/ha) and one inorganic fertilizer combination (250 urea kg/ha and 250 ammonium phosphate kg/ha). These mechanical properties were determined at at two gravimetrical water contents (WCs) (17.1 and 20.9% db) on remolded soil samples. The experimental designs were consisted of: 1) factorial design (organic manure type ´ organic manure rate) and 2) orthogonal contrasts: i) control with inorganic fertilizer treatment and ii) control and inorganic fertilizer with factorial group in a completely ranomized design with three replications. Plate sinkage test (PST) and confined compression test (CCT) were used for determination of the pre-compaction stress and compression index. In this research, Three different models were fitted to log (stress)-sinkage data for PST and log (stress)-strain data for CCT with programming in Matlab software. After fitting the models to the data, the pre-compaction stress were obtained using three methods consisted of i) cassagrand, ii) Maximum curvature and iii) intersection of virgin compression line with x-axis. Soil shear strength was obtained using direct shear test. The remolded soil sample was preloaded by a stress of 00 kPa for 30-min. The result showed that there was a significantly linear and positive relationship between SOC and SL, PL, LL or friability index (FI=PL-SL) whereas the relationship with the soil bulk sensity (BD) was significantly negative. The soil texture and plastic index (PI=LL-PL) were not affected by adding organic matter to the soil. The application of inorganic fertilizer increased all measured parameters while the increase was not significant for PL and SL as compared with the control. The soil BD varied from 1.03 to 1.37 Mg m -3 . The lowest BDs were recorded in 100 Mg ha -1 sewage sludge and compost treatments whereas it was the highest in inorganic fertilizer treatment. The PL varied from 19 to 30% (d.b.). With one percent increase in SOC, the FI was increased by 3.9%. The Casagrande’s method showed highest val