Drill, also called a seeder, is a tractor-drawn machine used to precisely place seeds into soil. The grain drill is the most common type. It plants seeds for small grains and grasses. The grain drill plants seeds at the same depth in narrow rows usually spaced about 4 to 10 inches (10 to 25 centimeters) apart. The mechanism consists of a disk or hoe opener, a hopper, seed metering devices, and press wheels or short chains. The opener digs furrows (narrow grooves) in the soil. The hopper is a large box that contains the seed to be planted. The seed metering devices are attached to the bottom of the hopper. They send measured amounts of seed through tubes into the furrows. The chains or press wheels cover the seeds with soil.
There are two types of drills—end-wheel and press-wheel. An end-wheel drill is supported by two wheels, one at each side of the machine. The wheels drive the metering devices by means of gears and chains. Press-wheel drills are supported by wheels mounted behind each plowing piece. These wheels drive the metering devices, close the furrows, and press soil around the seed. Drills may also be equipped with devices that plant seeds of a wide variety of crops, including alfalfa, clover, peas, and sunflowers. Some drills can also distribute fertilizer.
