a machine for the uniform sowing of crop and grass seed by depositing the seeds in the soil at the required depth. Planters can also be used for sowing tree seeds in nurseries and for depositing mineral fertilizers in the soil.
Planters are classified according to the sowing method. Seed drills deposit seeds continuously using the row, narrow-row, wide-row, or band seeding method. Checkrow planters deposit clusters of seeds at the corners of squares or rectangles. Hill-drop planters distribute clusters of seeds in rows. Single-seed planters sow individual seeds at uniform intervals in wide rows. Broadcasters scatter fertilizers and seeds, such as grass seed for improving natural pastures, onto the surface of a field.
A distinction is made between general-purpose and special-purpose planters. General-purpose planters are used for sowing seeds of various crops; for instance, planters designed for grain seeds and grain-and-grass seeds can be used for sowing seeds for grain, bean, and olive crops, grass seed, and seed for bast crops. Special-purpose planters are designed for sowing seed for a single crop or a limited number of crops, for example, beet, cotton, corn, and vegetable crops. Planters may be combined with fertilizer attachments that deposit mineral fertilizers in the soil.
Planters are also classified according to the traction method used as tractor-driven (mounted or trailer-type), horse-drawn, or manually propelled. Only tractor-driven planters are manufactured in the USSR.
Each planter has one or two hoppers or several separate boxes for the seeds. A seeding mechanism feeds the seeds at a uniform rate from the hopper or boxes to seed spouts. Shares form furrows in the soil, and the seeds are deposited in the furrows. Covering devices deposit soil in the furrows and level the surface of the field. Some planters have stirrers located in the hopper; the stirrers prevent the seeds from sticking together in clumps and ensure better feeding of the seeds to the seeding mechanism. In broadcasters, a flat distributing device is mounted behind the seeding mechanism; the seeds fall uniformly from the device onto the field. The working elements, that is, the seeding mechanisms and stirrers, are rotated by a direct drive (in mounted planters) or by a support-wheel drive (in trailer-type planters) using chain or gear drives. Foreign planters use similar engineering designs.
In the USSR other types of planters are also used for planting crop seeds. They include combination planter-plows, planter-cultivators, and planter-stubble plows. Planter-plows are equipped with a plow body, seed hoppers with seeding mechanisms, and seed spouts. The machines simultaneously plow and deposit seeds in the furrows formed by the plow body. Planter-cultivators are designed to work soil previously worked by machines without moldboards; they are also able to plant seeds in stubble land. They simultaneously sow, loosen the soil, cut weeds, deposit mineral fertilizer in the rows, and turn over the seeded rows. Planter-stubble plows have stubble disks and spool-type seeding mechanisms with seed spouts. The seeds pass through the spouts into furrows formed by the disks and are later covered with soil.