Laboratory simulation of the surface morphology of self-mulching and non self-mulching vertisols. I. Materials, methods and preliminary results

To date, the definitions of ‘self-mulching’ in Vertisols describe the phenomenon only in the air-dry state with no details of the dynamics of the system. A laboratory study was carried out to simulate the field morphological features of the soil surface of three Vertisols, one self-mulching and two non self-mulching. The soils differedin shear strength in the field, clay type, ESP and exchangeable Ca/Mg ratio. The laboratorysimulation involved both repeated wetting/drying cycles with 6 mm of water every 48 h, anda continuous drying phase. These were imposed on ponded and puddled samples of thesoils. With repeated wetting and drying the self-mulching soil developed a surface with amore complex organization of structural features than either of the non self-mulching soils.The self-mulching soil generated a granular structure and developed the widest cracks. Mostelements of the surface morphology observed in the field were achieved in the laboratorysimulation