Harrow (tool)

In agriculture, a harrow is a farm implement used for surface tillage. It is used after ploughing for breaking up and smoothing out the surface of the soil. The purpose of harrowing is to break up clods and to provide a soil structure, called tilth, that is suitable for planting seeds. Coarser harrowing may also be used to remove weeds and to cover seed after sowing. Harrows differ from ploughs, which cut the upper 12 to 25 centimetre (5 to 10 in) layer of soil, and leave furrows, parallel trenches. Harrows differ from cultivators in that they disturb the whole surface of the soil, while a cultivator instead disturbs only narrow tracks between the crop rows to kill weeds. There are four general types of harrows: disc harrows, tine harrows (including spring-tooth harrows, drag harrows, and spike harrows), chain harrows, and chain-disk harrows. Harrows were originally drawn by draft animals, such as horses, mules, or oxen, or in some times and places by manual labourers. In modern practice they are almost always tractor-mounted implements, either trailed after the tractor by a drawbar or mounted on the three-point hitch. A modern development of the traditional harrow is the rotary power harrow, often just called a power harrow. In modern mechanized farming, generally a farmer will use two harrows, one after the other. The disk harrow is used first to slice up the large clods left by the mould-board plough, followed by the spring-tooth harrow. To save time and fuel they may be pulled by one tractor; the disk hitched to the tractor, and the spring-tooth hitched to, and directly behind, the disk. The result is a smooth field with powdery dirt at the surface. In cooler climates the most common types are the disc harrow, the chain harrow, the tine harrow or spike harrow and the spring tine harrow. Chain harrows are often used for lighter work such as levelling the tilth or covering seed, while disc harrows are typically used for heavy work, such as following ploughing to break up the sod.

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Related concepts (16)

Cultivator

A cultivator is a piece of agricultural equipment used for secondary tillage. One sense of the name refers to frames with teeth (also called shanks) that pierce the soil as they are dragged through it linearly. It also refers to machines that use the rotary motion of disks or teeth to accomplish a similar result. The rotary tiller is a principal example.

Tillage

Tillage is the agricultural preparation of soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shoveling, picking, mattock work, hoeing, and raking. Examples of draft-animal-powered or mechanized work include ploughing (overturning with moldboards or chiseling with chisel shanks), rototilling, rolling with cultipackers or other rollers, harrowing, and cultivating with cultivator shanks (teeth).

Disc harrow

A disc harrow is a harrow whose cutting edges are a row of concave metal discs, which may be scalloped or 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 residue. It consists of many carbon steel discs, and sometimes longer-lasting boron steel 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").