A harrow is a farm tool. It is an implement for breaking up and smoothing out the surface of the soil. In this way it is different from a plow, which cuts deeper into the soil. A plow also lifts up the soil and tips it over, but a harrow works mostly by cutting into the soil and breaking it up. Harrowing is often carried out on fields to follow the rough surface left by plowing.[1]
The purpose of this harrowing is generally to break up clods (lumps of soil) and to provide a finer finish, a good tilth or soil structure that is good for planting seeds. It may also be used to remove weeds and to cover up seed after sowing.
Harrows differ from cultivators in that they disturb the whole surface of the soil, instead of disturbing only narrow trails that avoid crop rows (to kill weeds).