10%· Soils, their properties and management. Soils. Fig-. 72 —Types of packers and pulverizers : (l), solid or barrel roller; (2), corrugated roller; (3), crusher and subsurface packer; (4), bar roller. 585. Clod crushers. — The aim of these clod crushers is to break up lumps. As to mode of action, there are several forms.