Relation between soil mechanical properties and pedogenetic processes and use intensity

Abstract

Soil formation processes and soil management affect its mechanical properties, due to wetting and drying cycles and machinery transit affecting particle arrangement, increasing contact areas and/or disrupting the structure. The relationships between mechanical properties, management and pedological development were evaluated in soils from the south of Chile. Samples from six soils were analyzed, grouped as Andisols and Ultisols, with different management and structural development. Soil samples were equilibrated at –1, -60 and –1600 hPa water tension. Bearing capacity was determined using the confined consolidation test with free drainage, applying loads from 6.25 to 1200 kPa. Cohesion and friction angle were determined from direct shearing tests, with normal loads smaller than 50 kPa and a speed of 1 cm h^-1. Mechanical properties of Ultisols were associated with soil management, with structural damage due to intense and long-term use. Preconsolidation value is a mechanical parameter related to soil pedological evolution. Soils were sorted from highest to lowest bearing capacity, associated with lower to higher amounts of precipitation. High mechanical strength is a result of intensified drying processes, resulting in higher values of bulk density in Andisols.