Tillage operation aims to create a favorable environment for seed germination of agricultural crop production practices. Physio-mechanical properties of soil directly affecting soil behaviors and determinants in initial conditions affecting soil failure. An absence in understanding how soil physio-mechanical properties affect agrotechnical operations at different tillage depths, especially in study area, and lacks insights into their associations and practical implications for optimizing tillage and soil health. This study presents an experimental investigation of the physio-mechanical properties of agricultural soil in Bukito Kebele, Loka Abaya woreda of Sidama Regional state, Ethiopia. The objective was to identify these properties under varying agro-technical soil depth conditions. Randomized Complete Block Design (RCBD) field experimental design was spotted to take soil samples using appropriate sample equipment and further lab analysis was conducted. Loka Abaya farm soil is loam, offering balanced texture for drainage, water retention, and nutrient availability. Moisture content reaches a maximum of 24.36%, with a linear relationship between soil depth and moisture content. The Atterberg limits of the soil (LL: 37.5-40%, PL: 25-27.5%, PI: 10-15%) indicate low plasticity and low clay content, consistent with loamy or silty soils. The results also show that soil cohesion is low in the topsoil (surface layers) but increases significantly at depths of 10-15 cm. Soil resistance decreases with depth due to reduced compaction and increased pore space in subsurface layers. Bulk density peaks at 1.28 g/cm3 at 10 cm depth due to high organic matter decomposition, then decreases to 1.20 g/cm3 at 15-20 cm, likely from reduced organic matter and root activity in subsurface layers. Correlations analysis reveals that soil moisture strongly increases with depth (r = 0.99, p < 0.01), indicating that deeper tillage may be necessary in arid regions to access moist soil layers. Sandy soils, which show a strong link between plastic limit and sand percentage (r = 0.97, p < 0.01), require adequate moisture during tillage to prevent erosion. Moist, cohesive soils are less compacted (r = - 0.92, p < 0.05) and easier to till, while cohesive soils resist penetration (r = - 0.90, p < 0.05), highlighting the need for efficient tillage equipment to minimize energy use. Overall, soil moisture, texture, and cohesion are critical factors for optimizing tillage practices and enhancing soil health. The study's site-specific nature limits its broader applicability, its focus on physical properties few mechanical property, overviews chemical and biological aspects, and further research is required to understand the long-term impacts of tillage on soil structure and productivity.

The mechanisms of soil failure on a microscopic scale are still not fully understood. Many soil behaviour models characterize a soil failure at the macroscopic level as single, continuous plane. Although on a microscopic scale, failure planes have a complex structure and are considered shear zones. This work aims to contribute to the microscopic analysis of the shear zones in residual soils. It describes the structures observed at the shear zones and correlates the microstructures to the macroscopic behaviour of a gneiss residual soil. The analyses interconnect the microscopic view with the stress-strain behaviour, stress path, and critical state line of the tested soil. The studied shear zone was generated in a laboratory during CAU triaxial tests. Images were obtained using a backscattered electron detector in a scanning electron microscope and subsequently subjected to digital image analysis. The variation in porosity and the degree of alignment of grains and lumps along the shear zones were evaluated. Smaller shear zones that make up a larger shear zone were also found. From the results, it was concluded that there is a strong influence of the strain level and effective confining stresses on the structure and geometry of the shear zones.