Model 21BZ-2.2/2.5/3.0/3.4 trailing and hydraulic lifting heavy-duty disc harrow with 20/24/28/32 discs is used for operation in the field as crop residue processing before tillage, breaking hardened and impervious soil surface, crushing and spreading straw in the field, shattering soil after tillage, planning the land and preserving soil moisture. It can be used as tillage instead of plough on the cultivated land. With the efficient productivity, reasonable utilization of the power, great ability of cutting and shattering the soil , the soil surface is smooth and loosening after harrowing, it is well suitable for heavy clay soil waste land and weedy field as well.