A harrow is what a farmer drags across a field after ploughing. Its job is to break up clods, level the surface, and uproot weeds so that seeds can be planted into a fine, even bed.

The design has barely changed in principle since Roman times, though the materials have. Early harrows were wooden frames studded with sticks. Today's versions use steel discs, spring tines, or heavy chains, pulled by tractors that cover ground at speed.

Common types

• Disc harrow: angled steel discs that cut and turn soil
• Spike harrow: rigid or spring tines for shallow cultivation
• Chain harrow: flexible links for levelling and spreading manure
• Rotary harrow: powered by the tractor's PTO for intensive seedbed prep

Harrowing also fits into conservation farming. A light pass can incorporate cover-crop residue or scratch the surface without burying the soil structure that no-till growers work hard to build.