Tools, devices and machines for sowing
A seed drill drops seed into rows in the right amount, spaces it evenly and covers it at the set depth in moist soil, and keeps sowing rows straight and level. They are divided into narrow- and wide-row, potato, hill and precision drills, and special ones for maize, cotton seed, beet, vegetables and grain; there are row and non-row (universal) kinds. A universal grain drill sows cereal and legume crops and also applies mineral fertiliser. Parts: seed boxes, sowing apparatus (roller or disc), seed tubes, coulters, covers and rollers. Seed is separated by a disc under the box and drops through the seed tube to the coulter. The coulter blades cut the soil and open a furrow, a wedge-shaped packer firms the furrow bottom, the cover fills the furrow with loose soil and a roller firms the top. Children do not approach a working drill and tractor; they only look at a stopped, switched-off machine with the teacher.
Modelling: show how a drill works with a card box, tube and plasticine: box = seed, tube = seed tube, plasticine blade = coulter. Do not touch a real machine.