Disk harrows differ from disk plows in that there is no tilt angle and several blades are mounted on a common axis called the gang. They are lighter and have smaller wheels than disk tillers. In disk harrows, the gang may be arranged in different configurations as shown in Figure 8.12. The arrangements may be single-action, offset, or tandem. It should be noted that the gangs are always in pairs with opposite disk orientation to balance the side draft produced by each disk. Disk harrows may be either mounted or pull type. Smaller units tend to be mounted while larger units tend to be pull type with wheels for transportation. Remote hydraulic cylinders are used to raise or lower the implement from the driver’s seat. Some very large units are designed to fold over for transportation. Pull type units with wheels allow for better depth control.

The size, weight, spacing, depth, and angles of the disks are selected based on the field conditions and the purpose of disking. Disk diameters range from 40 to 80 cm, and weights range from 20 to 200 kg/disk. Disking with larger disks should be followed by lighter disks for final seedbed preparation. Disk spacing increases with disk diameter. Narrow disk spacing of about 18 cm is used for final seedbed preparation when the ground is not hard with little surface residue. Disk spacing of about 23 cm is used for mixing of chemicals or cutting of surface trash. Spacing of about 28 cm and higher is needed for harder soils or when heavy surface residue is present. The operating depth is determined by the soil conditions and the weight per unit disk of the plow. The gang angle varies from 15° to 35° as measured from a line perpendicular to the line of travel. Gang angles may be changed to meet the field conditions. Increasing the gang angle makes the disks more aggressive, increasing their depth and power requirement.

Figure 8.12 – Gang arrangements for three general types of disk harrows