Disc harrow

Before invention of the modern tractor, disc harrows typically consisted of two sections, which were horse-drawn and had no hydraulic power.

Overuse of disc harrows in the High Plains of the United States in the early 20th century may have contributed to the "Dust Bowl".

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.

Disc harrows incorporate remaining residue into the top soil, promoting the rapid decay of the dead plant material.

A disc harrow is the preferred method of incorporating both agricultural lime (either dolomitic or calcitic lime) and agricultural gypsum, and disc harrowing achieves a 50/50 mix with the soil when set correctly, thereby reducing acid saturation in the top soil and so promoting strong, healthy root development.

Lime does not move in the soil, and this poses a critical challenge to sustainable zero-till farming, especially considering that chemical fertilizers are generally used by farmers around the world.

Once worn down too small to be of further use in harrows, the hardened steel discs have been adapted to form the blades of hand tools for wildland firefighters, farmers, and trail-building crews.

Lighter secondary disc harrows are primarily used to break down soil clods into smaller pieces.