Cultivator/Drill Combinations

Many arable farmers use a cultivator and drill combination on ploughed land to prepare a seedbed and sow the crop in a single pass. A more recent development makes it possible to plough, cultivate and drill at the same time with one tractor.

The most common type of cultivator/drill combination consists of a drill unit either mounted on a three-point linkage attachment on a power harrow or towed behind it with a bridge drawbar system. A power take-off shaft extension from the power harrow is provided when a pneumatic or air drill is used. Some models have a linkage arrangement which lifts the drill forwards over the harrow to bring its weight nearer the tractor. This improves the stability of the outfit in the transport position.

Power harrows have a high power require­ment and, where soils are suitable, many farmers prefer to use a tined cultivator and drill combination. These machines, usually built around a spring tined cultivator, are made in various widths with hydraulically folded wing sections on the wider models. High speed cultivator and drill combinations with a number of tillage implements and an air drill on a single chassis provide an alternative system of minimal culti­vations. These machines are used to prepare a tilth and sow seed on ploughed land or cultivate the soil and drill into a cloddy or trashy surface. An example of this type of drill, as shown in Figure 10, is carried on the packer roller (A) at the front and zero pressure rubber tyred roller (B) at the rear. Two rows of cultivator tines (C) are placed in front of the packer roller and four staggered rows of coulters (D) follow it. A land wheel (F) drives the metering unit in the hopper (E) and plastic seed tubes carry the seed to the coulters. The seed is covered by a row of inde­pendently mounted tines (G). The hopper is attached to the chassis by a closed hydraulic circuit suspension system so that its weight is distributed equally across the full width of the drill. This gives an even sowing depth to all coulters, no matter how much grain there is in the hopper.

Figure 10. A 3 m version of this high output combination cultivator drill requires a 75 kW (100 hp) tractor and the widest model with an 8 m sowing width needs a tractor of at least 185 kW (250 hp).

Figure 11. The grain drill, attached to the linkage on the power harrow, is lifted above the harrow for transport.

Figure 12. This studded roller force feed drill is attached to a three-point linkage on the spring tine cultivator and packer roller. A hydraulic ram lifts the drill above the harrow for transport.

Figure 13. High work rates can be achieved with a cultivator-drill combination. The drill has a mechanical metering system and the seed is delivered pneumatically to the coulters.

Direct Drills. The technique of direct drilling means that the seed is placed directly into stubble or another undisturbed surface. Some direct drills have very robust disc coulters which cut slots in the soil. Seed tubes place seed in the slots which is then covered with soil. Other direct drills have narrow shares carried on heavy duty spring tines with seed tubes attached to them. Another system employs a seeding mechanism attached behind the cutting table on a combine harvester which broadcasts seed into the stubble (Fig. 14).

Figure. 14. Oilseed rape can be direct drilled by broadcasting it directly into the stubble

behind a combine harvester cutter bar.

Weed control can be a problem with direct drilling and it is usual to spray off surface vegetation a few days before the field is drilled. Until recently, when the practice was banned, straw and stubble burning provided an excel­lent surface for direct drilling.

Combine Drills. Although no longer widely practised, some farmers prefer to drill grain and fertiliser at the same time with a combine drill. Most mechanical force feed drills have a roller feed mechanism for the fertiliser, similar to that for the seed, but the hopper is much larger with separate sections for the grain and fertiliser.

Combine drills with a pneumatic feed system have separate metering units and hoppers for the grain and fertiliser. Seed or fertiliser can be carried in the front and rear hoppers depending on the required application rates. The same type of metering unit is used for seed and fertiliser.

Figure 15. This pneumatic feed combine drill has a front-mounted hopper with a second one above the power harrow and drill combination.

When seed is carried in the front drill hopper it is blown to a cyclone which removes the air before it passes to a metering mechanism on the drill (Fig. 14). Another feed mechanism meters fertiliser from the rear hopper at the required rate. The seed and fertiliser are then conveyed by an airflow to the coulters.

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