ABSTRACT PHYSICAL properties of wheat (initial density and moisture content) and the boundary conditions (axial strain rate and confining pressure) affected both the axial and volumetric stress-strain en masse behavior in triaxial tests. Measured stress-strain trends indicated that the deviatoric stress at failure was larger for the test samples with higher density; whereas, the ratio of deviatoric stress at failure decreased as confining pressure increased. Fourteen elastoplastic parameters, as used in the Lade constitutive model, were determined for wheat en masse from axial and isotropic compression triaxial tests at two initial densities, one moisture content and two axial strain rates. The y} test validated the use of Lade model, at 0.05 level of significance, for simulating wheat en masse load response within the range of test conditions studied.