Traditionally, land that was being converted from pasture into a crop was ploughed, which turned over the top 15 centimetres of soil. The land was left until the existing vegetation had died and then the surface was worked with equipment such as a grubber or set of harrows – tools that are dragged over the soil to break down the clods.
Often this equipment would have a roller or crumbler device that further reduced the size of clods, and compacted and flattened the soil surface to reduce moisture loss. Depending on the structure of the soil, two to four passes over the paddock might be required after ploughing to produce a seedbed with small, even-shaped soil particles.
There is a wide range of modern cultivation practices. For example, using power harrows or rotary hoes, which have moving spikes that are driven by the tractor’s power. These require powerful tractors and are energy-intensive, but may only require one to two passes to produce a suitable seedbed. This can reduce the time between one crop and the next.
Once a suitable seedbed has been produced, the seed is sown at the correct depth using a drill. Fertiliser may also be applied through the drill.
Although seeds should be evenly spaced, this is less important for crops like wheat, barley and peas than for maize and vegetable crops.
After sowing, the soil should be compacted with a roller to ensure good contact of the seed with the soil, and to prevent moisture loss.
About 75% of wheat is sown in autumn (May) and the rest in early spring (August/September). Barley is usually sown in mid-spring (September/October).
Towards the end of the 20th century some farmers began direct drilling, which doesn’t require ploughing. Existing vegetation is sprayed with herbicide and, after it has died, the seed is drilled directly into the soil. This saves cultivation costs and helps retain soil moisture.
Plant breeders select individual plants with desirable characteristics – such as high yield, good quality, and pest or disease resistance – and breed from those plants. After several generations of crossing and selecting these breeding lines, they will be tested in large plot and field trials. Finally, once the breeders are satisfied that their selection has significant advantages, the new cultivar is named and registered with the Plant Variety Rights Office. Some commonly used wheat cultivars are Regency, Domino, Monad, Torlesse and Hussar.
Some direct drills have knife-like T-shaped tines (spikes) to create small slots for the seed and fertiliser, while others create a V-shaped furrow. Rollers then cover the seed and compress the topsoil. As with conventional drilling, this is important to reduce moisture loss.
The cultivation and planting methods used depend on the soil type, the previous crop and the available equipment. Cultivation and drilling account for around 20% of the costs of producing an arable crop. Seed makes up around 10–15% of the costs, so it is important to create the best conditions for seed to grow into productive plants.