Snapshot

A disc harrow is a harrow whose cutting edges are a row of concave metal discs, which may be scalloped, set at an oblique angle. It is an agricultural implement that is used to till the soil where crops are to be planted. It is also used to chop up unwanted weeds or crop remainders. It consists of many carbon steel discs, and sometimes longer-lasting boron discs, which have many varying concavities and disc blade sizes and spacing (the choices of the latter being determined by the final result required in a given soil type) and which are arranged into two sections ("offset disc harrow") or four sections ("tandem disc harrow"). 

The discs are also offset so that they are not parallel with the overall direction of the implement. This arrangement ensures that the discs will repeatedly slice any ground to which they are applied, in order to optimize the result. The concavity of the discs as well as their offset angle causes them to loosen and lift the soil that they cut. Modern disc harrows are tractor-driven and are raised either by a three-point lift or hydraulically by wheels. The large ones have side sections that can be raised vertically or that fold up to allow easier road transport or to provide better storage configurations.