A planter is a farm implement, usually towed behind a tractor, that sows (plants) seeds in rows throughout a field.[1] It is connected to the tractor with a drawbar or a three-point hitch. Planters lay the seeds down in precise manner along rows. Planters vary greatly in size, from 1 row to 54, with the biggest in the world being the 48-row John Deere DB120. Such larger and newer planters comprise multiple modules called row units.[1] The row units are spaced evenly along the planter[1] at intervals that vary widely by crop and locale. The most common row spacing in the United States today is 30 inches.[1]

A Kinze 2200 planter
Various machines meter out seeds for sowing in rows. The ones that handle larger seeds tend to be called planters, whereas the ones that handle smaller seeds tend to be called seed drills, grain drills, and seeders (including precision seeders). They all share a set of similar concepts in the ways that they work, but there is established usage in which the machines for sowing some crops including maize (corn), beans, and peas are mostly called planters, whereas those that sow cereals are drills.

On smaller and older planters, a marker extends out to the side half the width of the planter and creates a line in the field where the tractor should be centered for the next pass. The marker is usually a single disc harrow disc on a rod on each side of the planter. On larger and more modern planters, GPS navigation and auto-steer systems for the tractor are often used, eliminating the need for the marker. Some precision farming equipment such as Case IH AFS uses GPS/RKS and computer-controlled planter to sow seeds to precise position accurate within 2 cm. In an irregularly shaped field, the precision farming equipment will automatically hold the seed release over area already sewn when the tractor has to run overlapping pattern to avoid obstacles such as trees.